HYGIENIC REQUIREMENTS TO PLACING, EQUIPMENT, MAINTENANCE AND USING OF SEPARATE STRUCTURAL SUBDIVISIONS OF DENTISTRY ESTABLISHMENTS.HYGIENIC ESTIMATION OF STAY PATIENTS IN HOSPITAL, OCCUPATIONAL HYGIENE OF MEDICAL WORKERS, INCLUDING DENTISTRY.METHODS OF ESTIMATION OF RADIATION DANGER AND PARAMETERS OF PROTECTION FROM AN EXTERNAL IRRADIATION.
BASIC REQUIREMENTS FOR EQUIPMENT OF DENTAL OFFICES, CLINICS, PHYSICIAN OFFICES, DENTAL OFFICES AND LABORATORIES
Requirements for premises and equipment:
In the dental clinic should have a list of key areas:
1. Entrance and vestibule (separately for children and adults).
2. Front, help desk, cloakroom, archive and sanitary unit.
3. Offices and Deputy Head (head of the medical unit), accounting, sister-room hostess, support staff, sanitary units on each floor. It is recommended that development corridors for unilateral or bilateral partial schemes.
1. Offices of dentistry:
- The minimum area - 14m2,
for every additional seat should provide 7m2, height cabinets - not
- In one office location is allowed up to 3 seats;
- Every workplace separating
opaque partitions height
- Izolovovani space for cooking and sterilizing materials should have an area of at least 8m2 and be equipped with fume cupboards.
2. Offices of dental surgery:
- In one study no more than 2 workplaces;
- Office should have at least 5 areas, namely:
- Expectantly -
- Preoperative - not less than 10m2;
- Operating - 27m2 (with 2 seats should provide additional 7m2);
- Sterilization - 8m2;
- A room for temporary postoperative patients - 7-12m2.
3. Massage prosthodontics:
- Office should have at least 4 areas, namely:
- Expectantly -
- Actually orthopedic surgery - not less than 14m2;
- Sterilization - not less than 8m2;
- A room for temporary stay patients after orthopedic surgery.
4. Dental laboratories:
Laboratories should be placed near the offices of Prosthetic Dentistry, which shall include in its order:
- Main room - no more than 15
technicians and not less than
- Hipsuvalna - 4m2 1 workplace;
- Solder - 4m2 1 workplace;
- POLIMERIC - 4m2 per workplace;
- Polishing - 4m2 1 workplace;-cast - not less than 11m2per 1 workplace;
- Facilities for receiving, weighing, storage and delivery of products from gold.
5. Massage physiotherapy department:
- Expectantly - not less than 6m2;
- Room for electro - at least 6m2;
- Room for hypnotherapy is not less than 25m2;
- Physiotherapy is not less than 12m2.
Basic dental offices have some construction features:
- Floor plank linoleum, sealed connections;
- The use of plastic plytochnoho not allowed;
- The basis of sex under the linoleum is protected against the penetration of mercury special solution;
- Linoleum flooring should
climb the walls to a height of
Wall-cabinets should be smooth with no cracks, all-area and the junction of walls, ceilings and floors should be rounded with cornices and ornaments;
- Wall cabinets dental surgery
and sterilization imposed tiles to a height of
Data on the requirements for air-conditioning and lighting cabinets dental clinics are presented in Table. 1 and 2
Table 1: Requirements for air-conditioning cabinets dental clinics
Temperature, ° C
air velocity, m / s
Cold and Transformation
16 — 21
40 — 60
21 — 25
40 — 60
Table 2: Requirements for lighting offices dental clinics
Luminiscent lamp, lux
Incandence lamp, lux
manipulation, the basic premise dental prosthetic laboratories
Offices Administration hipsovochni,
2 — 3
Tasks of hospital hygiene:
Ø Preference to acceleration of recovery the patient, achievement of indemnification of functions, medical and psychological rehabilitation.
Ø Achievement for psychological and somatic comfort for the patients during stay in hospital institutions.
Ø Prevention of nosocomial infection
Ø Maintenance of epidemic and radiologic safety.
Ø Maintenance of healthy occupational environment for the medical personnel.
Ø A regulation of use of new disinfectants, detergents, polymeric materials, newest equipment and technologies in medical institutions.
Ø Formation of bases of a healthy life style at the personnel and patients MPI.
Ø Minimization of influence on an environment for construction and operation of medical institutions.
The main characteristic of all medical-preventive institutions is presence so called "hospital environment ". Hospital environment is a set of all factors of physical, chemical, biological and information nature, which carries out influence on an organism of the patient during treatment. There are microclimate of hospital premises, various radiation end wave influences, medicines, antiseptics and polymer material, special hospital strains of bacteria. These factors define dynamics of medical rehabilitation and health of patient and staff.
Before to buid any health facilities it’s recommended to arrange their planning with the authorized general plans and projects on the basis of the circuits of area development.
Fig. Situation plan of hospital
When they develop the general plans of
medical-preventive institutions it is necessary to take into account local
climatic conditions and to provide measures on protection of building and
nearby area from the adverse external factors. A choice of the ground area for
an arrangement of houses of hospitals, maternity houses and others in-patient
institutions should be agreed with local authorities and institutions of
environmental health service. The medical institutions have to settle down in
residential or suburb zones in conformity with the authorized plan and projects
of detailed planning of the residential area in view of its functional
application. General hospitals and maternity houses should be placed outside of
the centre of cities and settlements, the hospitals of emergency care have to
be under construction in view of the maximal approximation to groups of the
population, which they are served. The specialized hospitals or complexes with
capacity for over than on 1000 beds for
the patient stay during long time, and also special hospitals
(psychiatric, tuberculosis and other) is necessary to place in a suburb zone,
Hygienic requirements for the patient care institutions planning and accomplishment
The patient care institution site development area is selected taking into account several reasons:
- a distance from the farthest settlements of the population service zone: land plot must be connected with population service zone favorably (patient must be taken to the hospital in no more than 30 minutes);
- a distance from the possible air or soil pollution sources; the sources of noise, vibration, EMF, the emission of the industries, airports, railway stations, speed motorways and other, taking into account their sanitary and protection zones and “wind rose”;
- usage of the existing green area (park, wood);
- a flat countryside or a flank of hill towards the Southern points and others.
The site land area depends on the power, specialization and system of the hospital group of buildings site development (table 1).
The most suitable form of the hospital group of buildings land site is a rectangular one – with the sides’ ratio 1:2 or 2:3. The long axis should be oriented from the East to the West or from the North-East to the South-West (it provides the hospital constructions wards’ orientation towards the Southern points, but the operating rooms, delivery rooms, laboratories and X-ray departments – towards the Northern points (to prevent dazzling and overheating by solar rays)). Selecting the area, one should take into consideration the possibility of the hospital constructions joining the existing systems of water, sewerage, electricity, gas and heat supply, passages and drive conveniences.
Systems of hospital site development are:
- decentralized (pavilion), when each department is situated in the separate building;
- centralized-blocked, when all departments are situated in one (semidetached) building;
- mixed, when the majority of departments are situated in the central building but some separate ones (infectious diseases, children’s, psychiatric departments and so on) – in the isolated buildings.
The drawback of the centralized system is the difficulty of nosocomial infections prevention, decreased time or impossibility of the patients to stay outdoors.
The mixed system, when the infectious, psychiatric and children’s departments are situated in the separate buildings, has none of abovementioned drawbacks, and that’s why it is the most suitable.
The site land project of the patient care institution includes the following zones:
- a zone of the patient care buildings for non-infectious patients;
- a zone of the patient care building with infectious diseases;
- a polyclinic zone;
- a zone of morbid anatomical department;
- a household zone;
- a landscape zone.
The infectious, obstetric, children’s, tuberculosis and psychiatric departments should have separate landscape zone of their own.
The hospital site housing density depending on the amount of beds should
not exceed 10 – 15 %. Up to 60 – 65 % of the area should be occupied by all
kinds of green area; 20 – 25 % - a household zone, passages and passageways.
The size of the landscape zone should be not less than
The distances between the hospital buildings should be the following:
between the walls with wards and
doctors’ rooms windows – 2.5 of the opposite building height but not less than
between the radiological building and
other ones –
the morbid anatomical building and a
household one – at the distance of
between the buildings’ flanks – not less than
The admission department for somatic patients (in the central building) and the rooms for the patients’ discharge should be joined together and should include: the examination room, sanitary inspection room, the wards for temporary admitted patients’ stay, the resuscitation and intensive care room, sometimes – the X-ray room.
There should be separate admission and discharge departments for the children’s, obstetric, infectious, dermatovenerologic, tuberculosis and psychiatric departments.
The admission departments areas depend on the amount of patients supposed to be admitted during 24 hours.
The sanitary inspection room is planned according to the current principle and consists of: the examination room, cloakroom, bath-and-shower room, dressing room.
In the infectious, dermato-venerologic and tuberculosis departments the admitted patient’s clothing is referred to the disinfecting department which is situated in the separate building within the household zone.
The laundry, central nutrition unit, boiler-room, garages and other hospital premises are also situated within the household zone.
Hygienic requirements concerning hospital departments
Each hospital department is intended for patients with similar diseases.
It should include: ward sections for 25–30 beds, with 6–8 wards for 2–4 beds
with the area of
The optimal ward windows orientation in the Northern hemisphere is the South-East or South. But there should be 1-2 wards with the orientation towards the Northern points for severely ill patients or patients with fever. Beds should be located parallelly to the light conductive wall for a patient to be able to turn back from the dazzling effect of the direct solar radiation. The natural lighting indices (near the internal wall) should be the following: the daylight factor – 1,3-1,5 %, the lighting coefficient – 1:4-1:6, the angle of incidence – not less than 27°, the angle of aperture – not less than 5°, the coefficient of depth of premises – not more than 2. The artificial lighting should be general, 30-60 lux, and the night light – 10-15 lux with lamps in the lower part of the walls.
The wards ventilation should be achieved by means of exhaust ventilation ducts, presence of window leaves and windows which can be opened; the modern hospitals should be equipped with air-conditioners.
In the infectious diseases units the following rooms should be equipped: box wards (with every bed isolation), semi-boxes (the isolated wards with common lavatory and bathroom), and absolute boxes (the isolated wards with lavatory and bathroom).
The operating block of a surgical department should be situated in the
blind-ended projection or in the separate outhouse of the hospital. In the
operating block there should be following rooms: the operating room –
In the surgical departments there should be pure and purulent dressing rooms.
There are some peculiarities of the children’s departments and hospitals, tuberculosis, psychiatric and other specialized patient care institutions’ planning; they are explained in the normative documents and can be learned if it’s necessary.
ground in hospital area must be clean, dry, without sharp differences a relief.
The hospital area should be placed in aerodynamic shadow, so that the velocity
of air movement did not exceed 5 m/s. They electrify the area, supply it with
waterpipes and water drain, border on perimeter and protect by a strip of green
plantings with width not less than
an arrangement medical and maternity institutions in residential zone it is
necessary to place them not closer than
The hospital area should be gardened and
comfortable. The area of green plantings and lawns has to make not less than 60
% of the general area and area of garden zone -
it is necessary to place not closer than
Hygienic meaning of vegetations:
v Protection against wind, dust and noise
v Optimization of microclimatic conditions: they give a shadow, normalize a humidity of air and make an aerodynamic shadow
v Bactericide influence of phytoncides on bacterial pollution of air
v Oxygenation of air
v Fixing of dust by a grassy lawn
v Architectural-planning meaning
v Aesthetic and psychohygienic meaning
v They can be a potential source of allergens
v Some plants are poisonous
v Danger of traumatisation with sharp and rigid stalks of plants, with heavy fruits etc
v Adsorption of dust particles by plants surface
area located in territory of settlements should have a strip of green plantings
with width not less than
The bushes should be in width not less than
Now they use 3 basic systems of building of medical institutions. They are distinguished by a various degree of centralization and isolation of functional departments.
The centralized system of building of hospitals is characterized by the maximal concentration of medical service. Usually the hospital house represents a multi-storeyed structure the separate departmentes and services situated at various levels in general architectural space. In Ukraine the hospital could not have more than 9 floors.
The basic advantages of the centralized system is:
Ø Economy. At the expense of the small area and absence of duplication of the basic building volumes, functional departments, and engineering networks, the charges on construction and technical equipment of hospital decrease.
Ø The reduction of the vertical and horizontal ways of movement of the personnel and patients allows to raise efficiency of medical process.
Ø The large concentration of scientific and technical resources allows to develop departrments on the basis of this centralized type hospitals, which give the qualified and specialized medical care.
In the same time for this system has some drawback:
Ø The raised risk of nosocomial infections. Difficulty of isolation of departments with a various structure, presence of ascending flows of bacterial aerosols, intensification of loading on hospital environment lead to increased risk of disease.
Ø Deterioration of conditions of hospital environment. High concentration of technical equipment makes excessing of noise level. The microclimate of the top floors could be overcooling because of power wind drafts.
Ø The architectural flexibility of the centralized system is low usually.
The decentrilized system is characterized by organization of various functional departments in separate houses.
The essence of pavilion system is the arrangement of separate functional departments in 2-3 floor-houses. The basic advantage of this system is:
· Good isolation of various departments, that allows to prevent occurrence of nosocomial infections,
· Good conditions for observance medical care regimen
However, nowadays they were compelled to refuse decentralized system. It is connected with:
· The large expenses on building works and technical equipment
· Reduction of garden zone
· Increase of the length of movement for the personnel and patients. There are some technical decisions for reduction of the routes of the personnel, in particular underground type of communication, but it does not solve a problem
Presently most perspective is the mixed system of construction. It unites features of centralized and decentralized system. It has the most flexible architectural planning.
The territory of hospitals, maternity houses and other in-patent institutions should have convenient access roads with a firm covering. Internal roads and foot paths should be covered by the concret or asphalt.
The optimum capacity of multiprofile hospitals is accepted in 600-800 beds (allowable - 1000 beds).
In the territory of hospitals there should be the following zones:
1. Zone of medical departments: for the infectious patient, medical departments for noninfectious patient, for pediatric departments, for patrimonial houses and maternity departments, psychosomatic departments, dermato-veneralogical departments, radiologic departments
2. OPD and administrative zone
3. Garden zone
4. Zone of court yard
Separate entrances to the various hospital zones should be provided. For emergencies they provide “Ambulance Road” – the entrance and exit for ambulance should create one-flow driving in and out of the hospital department area.
The patologo-anatomic departments with a funeral zone should be isolated from ward departments and they should not be looked through windows of the departments, from the hospital garden, and also through windows of inhabited and public houses.
Distance between houses with windows of chambers has to make 2,5 heights of opposite house, but not less than 24.
Infectious, maternity, psychosomatic, dermatovenerologic and the children's departments of hospitals should be placed in the separate houses. If hospital has the out-patient department, the last should situate close to periphery of a site.
Before front entrances to the hospitals,
polyclinics, SES, dispensaries and the maternity houses they are provided
grounds for the visitors by the account
In territory of infectious hospital (department) should be allocated a "clean" and "dirty" zone isolated by one from one strip of green plantings. On departure from a "dirty" zone there should be stipulated platforms for desinfection of transport.
Buildings of out-patient institution as rule do not have more than 5 floors.
The departments of children's hospitals for children till 3 years with the mothers should be placed not above than fifth floor, the chambers for infants and children's psychiatric departmentes - are not higher than the second floor.
Cleaning of territory has to be carried
out daily. For collecting of wastes and household dust they establish
containers with covers. These containers should be disinfected and washed
properly. Distance between a ground for dust container and ward and
medical-diagnostic departments should be not less than
Planning of medical and maternity hospitals have to provide optimum sanitary - hygienic and antiepidemic modes and conditions of patient stay, work and rest of the personnel.
Structure of institutions and planning of its premises have to exclude an opportunity of crossing or another contact of "clean" and "dirty" flows.
Maternity houses - specialized stationary institutions, which provide health care for pregnant women in childbirth, recently delivered women, newborns, to the gynecologic patients (at presence of gynecological department).
They offer to place in basement of medical-diagnostic departments warehouses, sanitary - household premises for the personnel (wardrobes, shower-room), sanitary care unit, buffets and restaurants for the personnel, central laundry, premises for collecting and sorting of a dirty linen, premises for desinfecting of bad pans, oil-clothes and beds, premises of preservation, regeneration and heating of a medical muds; storehouse of radioactive dross and linen polluted with radioactive substances.
It’s forbidden to place medical-diagnostic departments, workshops using hazardous materials and reception wards in basement of hospital.
X-ray rooms and laboratories of radiodiagnostic should not be adjacent on a horizontal or vertical with chambers for the pregnant woman and children. It is forbidden to place x-ray studies under premises of shower, lavatories and other possible sources of water.
Premises of hospitals, maternity houses and others should be illuminated by day light. The illumination by the second light or only artificial illumination is used in premises of barns, toilets, bathrooms, enema room, rooms of personal hygiene, shower and wardrobe rooms for the personnel, thermostate, microbiological banks, preparation and operational, apparatus, narcosis, photolaboratories and some other premises which do not require natural illumination. Operation room projected with natural illumination, it is necessary to focus on the north.
The corridors of ward sections
(departments) should have natural illumination. Distance between light pockets
should not exceed
For protection from blinding actions and overheating in summer time from direct solar rays in medical stationary located in 3 and 4 climatic areas aperture wrapped up on sector of horizon 70-240º of northern latitude they have to use solar protection equipment.
Table 7.3 Window orienting in the hospitals
< 45 N
45 - 55 N
> 55 N
Operation, IT wards, delivery room
N, NE, NW
N, NE, NW
N, NE, NW, E
N, NE, NW, SE, E
N, NE, NW, SE, E
N, NE, NW, S, SE, E
TB and Infection wards
S, SE, E, NE*, NW*
S, SE, E, NE*, NW*
S, SE, SW, NE*, NW*
* — not more than 10% of all beds
The artificial illumination should answer assignment of a premise, be sufficient, regulated and safe, to prevent the dazzling and other adverse influence on the human organism and internal hospital environment.
The general artificial illumination is necessary stipulated in everything, without exclusions, premises. For illumination of separate functional zones and workplaces, they use local illumination.
The artificial illumination of hospital premises is provided with luminescent and bulb lamps.
We use combined lighting (general and local illumination) in the hospital wards. In one-bed chambers the general illumination is provided. In chambers of children's and psychiatric departments, intensive therapy, the reanimation, in postoperation chambers they provide only ceiling fixtures of general illumination. For night shifts they use lamps in niches near doors
The emergency illumination is provided at dressing, manipulation, procedural, ATS, assistant, drugstores, reception wards, laboratories of the urgent analysis, X-ray-operation room, and on the nurse stations.
All hospitals should be equipped by centralized water supply, ssewege system, ventilation (if it’s necessary - by systems of air conditioning), rubbish-collector with rubbish chamber, elevators as needed, electrical and telephone networks. If necessary they use centralized vacuum rubbish collectors and other equipment.
Fig. General plan of hospital
For waste treatment from hospital catering service in hospitals they establish fat-catching device. The treatment of waste from hospitals including infectious is carried out by municipal sewer system. At absence of municipal sewege systemthey use system of local waste treatment.
For all health facilities should be provided reserve (emergency) hot water supply. They could use electrical boilers or second input of hot water supply. For heating it’s used water heating system with maximal water temperature in heating devices 85oC (Using water steam heating in the hospitals is prohibited).
The heating radiating concrete panels can be used in following premises: operation, preoperation, resuscitation wards, narcosis, delivery, premises of electrolight treatment, psychiatric departments of hospitals, therapy rooms, rooms for premature babies, injured children, little children and newborns infection wards, combustiological wards, complete and incomplete boxes, premises of blood bank, storerooms for sterile materials and medications, x-ray rooms, laboratories and experimental - biological clinics (vivaria).
The toilets for the patient should be equipped with cabins, hangers, drying devices for hands, mirrors. In lavatories of female ward sections there should be equipped cabins of women hygiene with ascending shower (bidet).
The quantity of sanitary devices (toilet pans) for the patient in ward departments of hospitals should be accepted at the rate of 1 device per 15 men and per 10 women, but not less than 1 device. The quantity of pissuare in male lavatories has to equate to quantity of another sanitary devises. The sizes of lavatory cabins for the patient should be not less than 1,5 (1,1) m with obligate opening of doors outside. In sanitary - household premises for the attendants it is necessary to accept:
1. Quantity of sanitary devices for the medical staff - not less than 2 devices for the women and 1 device for the men; but not less than 1 sanitary unit on each department
2. Quantity of shower cabins - 1 shower cabin per 10 employees in infectious and phthysiatric departments, in other departments - 1 shower cabin on 15 employees in the largest shift. If less number of the personnel it is necessary to provide 1 shower cabin on department.
Lavatory for the patient in ward departments for hundicapped patients should have special equipment (racks, folding ), that the seriously ill patient can use of sanitary devices.
The houses of medical and patrimonial houses should be equipped with systems of balanced ventilation, except for infectious departments. In the last should be established the exhausting ventilation. The exhausting ventilation from chambers has to be carried out through individual channels, which prevents of air movement by the vertical.
They use exhausted from operational,
narcosis, resuscitation, patrimonial and X-ray rooms, as a rule, from two
zones: 40 %- from upper zone (
Ventilation systems in operation, narcosis, resuscitation, maternity and other wards with severe sanitary should be equipped with bacterial filters.
Reception ward of hospital has following functional tasks:
· Reception, registration and distribution of patients
· Previous diagnostics
· The decision of a question about necessity of in-patient or out-patient treatment
· Sanitary treatment of patients
· Prevention of communicable diseases
· Shifting needed patients to other health facilities
· Discharging the patient and distribution of an information.
The number of patients are receipted by the reception ward depend on the number of beds in the hospital and its specialization::
· 2 % of beds number - in TB, mental and rehab hospitals
· 15 %- in emergency hospitals and maternity houses
· 10 %- in other hospitals.
In obstetric departments the reception premises (examination room, sanitary treatment unit) should be provided as combined for physiological department and department of a pathology of pregnancy and separately for observation and gynecologic departments. The movements the patient of all departments, including stairs and elevators, should be isolated one from one.
If it’s necessary they organize traumatological shifts, their offices should be placed on the ground floors of houses.
For reception of the infectious patient they provide isolator room which connected to examination room of the ward.
Ward department is the basic functional structural element of in-patient medical institutions. The basic types of ward departments is: noninfectious department (for adult and children) and infectious departments, maternity department
If children departments has 60 or more beds they should be placed in separate buildings. Infectious and TB departments are placed only in separate buildings.
Ward department consists of ward sections and general premises located between the sections. The general premises include the medical and diagnostic offices, catering service premises etc.
The ward section represents the isolated complex of rooms and medical-auxiliary premises providing care for patients with homogeneous diseases. The quantity of beds in ward section, as a rule, is not less 20 and no more than 30 (except for psychiatric).
The quantity of 1 bed rooms in observation obstetric department, department of a pregnancy pathology and also in hematological, neurosurgical and urologic departments for adult persons and children should be not less than 15 %, and in others departments - not less than 7 % of quantity of beds in department.
The quantity of 2 beds rooms in the specified departments has to make not less than 15 %. In all other departments project not less than two 3 bed rooms in each section.
The best ratio is 20%of one-bed, 20% for two-bed and 80% for three and four-bedrooms.
In infectious stationary basic structural unit of ward department could be not a ward, but complete or uncompleted box or boxed room. Boxes provide a complete isolation of the patient. There are 1-2 bed boxes using in Ukraine.
Box has two exits: to the department and to outdoor environment. The patient never leave box through the department door, they pass only through external exit with tambour. The access of the medical personnel to box is provided from a "conditionally clean" corridor through sluices, where medical staff should change their gowns, wash and disinfect hands. The doors in the sluices should be placed on the slanting line. Boxed department have the largest maneuverability and carrying ability, it is important for small departments.
Incomplete boxes distinguish from boxes because they have no an external exit. They also are provided on 1 and 2 beds. The mode of non-boxed department differs from boxed one by that the patients are brought in incomplete boxes through a general corridor department. In boxed departments it is recommended to use 25 % of all beds in boxes per 1 bed, other - in 2 beds boxes. In everyone ward section should be provided two incomplete boxes on 1-2 beds.
In noninfectious departments for children older one year and for adults they use rooms having not more than 4 beds. Capacity of rooms for infants, and also for newborns in observation obsteric department should be not more than on 2 beds each.
Recommended percent of boxes in section for children younger 3 years is 100 %.
At presence of the gynecological departments in structure of health institution it should be isolated from obstetrics and other “clean” departments. Women in the childbirth and pregnant women are divided into 2 flows in the filter of reception department . One flow is made by women in childbirth and pregnant women, which are directed at department of a pathology of pregnancy and physiological department, other - in observation department.
The reception in observation department of the maternity house is for the pregnant women and women in the childbirth who have:
· a fever (temperature of a body 37,6 oC and more without other expressed symptoms)
· long waterless interval (waters break in 12 and more hours before the reception in hospital)
· trombophlebitis of any localization (acute or chronic form in a stage of an exacerbation)
· inflammatory diseases of kidneys and urine tracts (acute stage, an exacerbation of chronic process during pregnancy, symptomless bacteriuria- 100000 CCU/ml and more)
· signs of any urogenital infection (colpitis, cervicitis, choriamnionitis etc)
· clinical or laboratoric data about TORCH infection (TORCH - toxoplasmosis, rubeola, cytomegalovirus, herpes, listeriosis, veneral diseases (STD))
· intrauterinal death of fetus
· acute respiratory disease (influenza, tonsillitis), signs of inflammatory diseases (pneumonia, otitis)
· skin diseases of infectious ethyology
· Tuberculosis (closed forms of any localization at absence of specialized hospital). (Pregnant women and women in the childbirth with the open form of a tuberculosis are should be hospitalized in the specialized maternity houses (department); if there are not presented - in boxes or isolators of observation department with the following transferring in tuberculosis dispensary)
· skin diseases (noninfectious)
· at absence of the medical documentation
· for an abortion on medical and social indication in ІІ the period of pregnancy
· malignant tumors
· women have the anomalies of development of a fetus, which revealed during pregnancy (at absence of specialized hospitals)
· women in the childbirth (in terms 24 hours after deliveries in case of childbirth outside of medical institution)
They transfer the pregnant women, women in the childbirth and women recently delivered if these women have:
· increase of temperature of a body 38oС and higher (at three times measuring)
· fever with not clear genesis (temperature of a body up to 37,5oС), that lasts more than 1 day
· postpartum inflammatory disease (endometritis, mastitis, wound infection т. і.)
· extragenital infectious diseases which do not require transferring in specialized in-patient department (ARVI, herpes etc.)
The pregnant women, women in the childbirth and women recently delivered, which suffer on infectious diseases, are subject to hospitalization and transferring in the appropriate infectious hospitals. The observation department should be placed or in the separate house, be isolated, above it there should not be an obstetric department.
At presence of gynecological department to it the separate reception is provided. Gynecologic department is necessary completely isolated from obstetric departments.
The operational block
The operational block is structural unit of hospital using for surgical operations.
The operational blocks are divided into general and specialized (traumatologic, cardiologic, neurosurgical). By an attribute of presence one department (aseptic) or two (aseptic and septic) operation room are divided on aseptic and combined.
The operational block has such functional zones:
І. The sterile zone: an operational room
ІІ. A zone of restrictions
· group of premises for preparation to operation: preoperation, wardrobe for overalls, narcosis room,
· group of premises for the equipment: apparatus room (AABC, hypotemia)
· group of premises of postoperation wards
· group of auxiliary premises, which contain also sluice at an entrance to operational room
ІІІ. A zone of the limited access:
· group of premises for diagnostic researches
· group of premises for preparation tools and equipment for operation: sterilization, instrumental-material (instrumental-financially)
· group of premises of the personnel: offices of the surgeons, office of the doctor - anaesthesiologist, room of the nurses-anaesthesiologists, room of attendants
· auxiliary premises: sluices at an entrance in septic and aseptic of department, room to the central board, plasters і and that similar
· warehouse premises: blood bank etc
Fig. The operational block
It is necessary to accept quantity operational in CR, interregional and urban regional hospitals: 1 on everyone 30 beds to a surgical structure and 1 on 25 beds in hospitals of emergency care. The ratio of septic and aseptic operational in operational blocks of general hospitals is necessary 1:3, but it is not less than one septic operational room per block.
The quantity of beds in post-operation ward is accepted as 2 bed per operation room. At presence of departments of anaestasiology and reanimation or the reanimations and ІТ department, postoperation wards are not provided, and their quantity is taken into account of beds of department of anaestesiology and reanimation.
Postoperation room are being placed in separate isolated section at the operational block, or in structure of branch anaestasiology and reanimation or the reanimations and ІТ department or it's isolated in structure of surgical department.
For maintenance of free transportation the
patient width of door apertures is necessary to be not less than
For control on the hospital environment they use following indicator of air pureness:
· Oxygen: 20-21 %. Very stable size, does not decrease even at intensive consumption (restoration for the infiltration).
· Carbonic gas:
· · very clean air < 0,05%
· · rather clean air < 0,07%
· · satisfactorily clean air < 0.1%
· Dust pollution:
· It is no more than 500 particles in 1 cm3
· ·clean air < 0,1 мг/м3
· dirty air > 0,15 мг/м3
· Oxydation of air:
· clean air - up to 6 mg О2/м3
· · is moderate - polluted - up to 10 мг О2/м3
· · dirty - up to 12 мг О2/м3
In canalized dwelling place there are:
1. complex of local treatment units with thermal decontamination in liquid and solid phase of waste. It has high effectiveness of decontamination. Power is about 100 m3/day
2. complex of local treatment units with septic-dehelminthizator. (25 m3/day)
3. complex of local treatment units with a septic (25 m3/day)
4. complex of local treatment units with the contact defenders (10-15 m3/day)
5. complex of local treatment units with a 2-level septic (100-150 m3/day). It's used in Odessa infectious hospital, for example.
6. complex of local waste buildings with a aerotank of continued aeration and mechanic aerator (400 (!) m3/day)
7. complex "Rapid Lock" (to 840 (!) m3/day)
8. complex of local treatment units with circular oxygenation channel (COC). It's used for waste treatment of tuberculosis hospitals if volume of waste is up to 700 m3/day
9. complex of local treatment units with emsher and biofilter. They use it for waste treatment of tuberculosis hospitals if volume of waste is up to 500 m3/day
10. complex of local treatment units with septic and biofilter ( for small tuberculosis hospitals, waste to 50 m3/day)
For canalized areas they use:
11. complex of local treatment units with ground fields of filtration (irrigation). The scheme are being used if volume of wastes is 50-100 m3/day and there is sandy soil.
of local treatment units with underground fields of filtration. Waste pipes
(drenas) is placed on the depth
13. complex of local treatment units with sand-gravel filters
14. complex of local treatment units with filtering trench
For waste treatment in tuberculosis hospitals they use two-stages of biologic purification.
Fig. Ward section of teraputic department
Fig. Ward section of children department
Fig. Ward section of infection department
Fig. Typical ward section
Nosocomial infections (i.e., infections acquired in the hospital) have become acute problem in human medicine because of increases in drug-resistant microbial strains and increases in the use of invasive procedures for patient support and monitoring. Compliance with handwashing protocols is perhaps the most important means of preventing nosocomial infection. Careful attention to aseptic technique and judicious use of antibiotics are also essential.
Nosocomial infections (NI) -infectious diseases connected to stay, inspection and treatment in medical-preventive institutions or reference (manipulation) in these for the help.
The concept "hospitalismus", which quite often use as a synonym of the term "hospital infection ", is wider and unites all diseases caused by specificity of environment of medical institutions. There are traumatic hospitalismus, mental (psychogenic) and infectious hospitalismus (NI). Joining to the basic disease, nosocomial infections worsen its decursus and prognosis.
Plasmid resistance is characterized by gradual change of types of sensitivity of many kinds of microorganisms for one or several antibiotics (tetracycline, ampicilline, cephalosporines etc.), and it’s typical for Enterobacteriaceae and Acinetobacter, Pseudomonas, H. influenzae. The resistance trasfer factor is conjugative plasmid. Sudden or gradual change of types cross resistance of one kind of microbs to two antibiotics (aminoglicoside + b-lactam antibiotic, tetracycline and aminoglicosides) characterizes stability connected to permeability. Last type of resistance is realized for Pseudomonas, Serratia, Staphylococci, Enterococci. Poliresistent strains are especially dangerous for children and weak persons, especially elderly people and patients suffering from immunodeficites of any origin. They represent group of risk.
The transfer of microorganisms can occur:
1. by an aerogenic way.
2. by fecal-oral way
3. by parenteral introduction
4. by the contact
HOSPITAL AND HOSPITALISM
The medicine is
one of the most abundant spheres of labor activity of society. It calculates
more than 170 medical specialties. In the system of public health services of
The work of the doctor should be referred to such kind of activity, which do not take part in production, creating material or spiritual values, at the same time ensures indispensable conditions for creation of such values, curing the people and reverting them to productive work.
The conditions and nature of labor activity of the doctors and other specialists of medical area require constant attention to protection of their health, because the activity of the medical worker bound with influencing both unfavorable working conditions, and dangerous factors of manufacturing environment on a workstation. These factors encounter a broad spectrum of manufacturing harmful factors.
а) Psycho physiological (psycho-emotional stress, specific work pose, excessive stress of analisatorysystems and other),
b) Physical (no comfortable microclimate, poor luminance of workstations, noise, chattering, ultrasonics, laser, radio irradiations,Ionizing radiation),
c) Biological (promoters of infection illnesses, parasite - insect, helminthes, Etc.),
d) Chemical (medical drugs, drug facilitiess and other).
It is known, that more than a half of professional diseases of the doctors - (59,8 % and more) is caused by physical and mental overstrain, and also the influence of the chemical factors.
Hygienic characteristics of occupational hazards for different medical personnel
The occupational exercise load and hazards of the surgical specialties doctors include:
- the number of surgical interventions – up to 150 per year in general surgery, 170 – in otorhinolaryngology, 370 – in obstetrics and gynecology. The number and complexity of the operations increase with the raising the level of the surgeon’s skill;
- the forced body position with the trunk frontal bending and the prolonged static tension of muscles of the shoulder girdle, back and stretched forward arms;
- the hot microclimate of the operating room with high streams of the radioactive heat from the artificial lighting sources (shadowless lamp);
- the ionizing radiation during the X-ray examinations, especially in traumatology, vascular surgery, neurosurgery;
- the toxic effect of the narcosis agents (nitrous oxide, halothane, chloroform, diethyl ether) and anesthetics;
- high mental and nervous-emotional exertion, connected with the complexity and duration of the surgical intervention, possible post-operative complications and responsibility for patient’s life.
Among the diseases afflicting the surgical specialties doctors with temporary disability the most widespread are the diseases of nervous system, cardio-vascular system, digestive system and acute respiratory diseases.
Among chronic diseases of these specialists such diseases, as the diseases of cardio-vascular system, neurasthenias, connected with high psycho-emotional and physical load should be mentioned. They are: angina pectoris, hypertension, vegeto-vascular dystonia and neurasthenia.
There are frequent diseases due to the prolonged standing at the surgical table: radiculitis, osteochondrosis, dyskinesia, varix dilatation of the lower extremities.
Surgeons’ disabilty or necessity to change their occupation in 60 – 80 % cases can be explained by chronic intoxication with narcotic agents and anesthetics, in 11 – 20 % cases - by the infectious diseases, 9 – 10 % cases - by physical and nervous overexertion.
Hygienic peculiarities of labour conditions and health status of the therapeutic doctors depend on the patient service forms. In case of polyclinic, district service, the leading role belongs to the excess physical load, which depends on the year season (amount of calls), the size of the doctor’s district and the type of the buildings (detached houses or many-storeyed buildings, elevator’s presence or absence). These specialists may also suffer from psycho-emotional exertion and different physical factors’ unfavourable effect – X-ray, UHF, ultrasound, laser and other diagnostic and physiotherapeutic measures, chemical harmful substances – the pharmacological preparations, from which nurses suffer more frequently.
Occupational diseases of therapeutic doctors, first of all of the phthisiatricians, infectiologists, specialists in skin and venereal diseases, helminthologists, the laboratory assistants at the bacteriological, virological, helminthological laboratories include the corresponding infections; phthisiatricians, X-ray doctors, radiologists suffer from dermatitis, eczemas, toxicodermia, melanomas, leucosis, skin cancer, radiation sickness; psychiatrists – psychoneurosis and others.
One of the main occupational hazards for dental doctors is their forced standing with the bending and turning trunk position which leads to the prolonged static tension of the corresponding muscles groups; noise and vibration due to drilling machine, sight exertion, blinding effect of the photopolymer lamp, penetration of mercury fumes from the mercury amalgam into the respiratory organs, fumes of the polymer materials solvents, danger of infection from the patient with the upper respiratory tract diseases during the incubation or convalescence stage, while performing the manipulations connected with the patient’s mucosal membrane or blood contact.
Abovementioned hazards can result in bearing disorder (34 – 45%), varix dilatation of the lower extremities (19 – 49%), signs of the vibration diseases (paresthesia, loss of hands’ temperature sensibility and perceptibility, Dupuytren's contracture).
The visual analyzer exertion can lead to the accommodation spasm, so-called false myopia, and sore eye.
AIDS, prion disease, hepatitis B and C can be transmitted through saliva, gum tissue and open wound.
Measures for improvement of the medical personnel labour conditions
One of the main conditions of the medical personnel labour protection and successful patient treatment is planning of architectural solution of the medical institutions, the base of this solution are the building norms and rules (BN&R-II 69–78 “Patient care institutions”). These norms consist of the list of all necessary premises depending on the hospital specialization, departments, their interposition, the area measures, cubic capacity, and special requirements to the location, area, protective properties of walls and floor and ceiling in the X-ray, radiological, and physiotherapeutic departments’ walls and overlap. Special norms and requirements to the buildings of the infectious, tuberculosis etc. departments and hospitals exist.
Sanitary norms and rules (SN&R) and the State Standard № 12.1.005 – 76 “The air of working zone. General sanitary and hygienic requirements” imply the creation of the optimal microclimate conditions in separate functional premises of hospitals, natural and artificial lightning, sanitary appliance etc. The modern operation rooms also are assumed to have the local ventilation (aspirators) in the zone of the anesthesiologist’s working place, the systemic laboratory control of the anesthetics concentration in the air. The most effective prophylactic measure against the anesthetics’ toxic effect for the operating brigade members is the transition to the intravenous narcosis and spinal anesthesia.
Personal protective equipment of body, eyes and respiratory organs are widely used.
To be protected from the ionizing and non-ionizing electromagnetic radiation, methods based on physical laws of radiation decay, which are stated in the legislative and organization direction are used. They include the protection by means of the radiation sources capacity limitation, distance, time, and shielding.
Thus, the legislation implies limit doses of the ionizing radiation, maximum allowable concentrations of radionuclides in the air of working zone (Norms of radiation safety of Ukraine (NRSU)-97), their maximal allowable activities at the working place and other.
In order to keep health of medical personnel with harmful labour conditions, the legislation establishes the half day:
- 4-hour-day – for medical workers directly connected with the bare radionuclides;
- 5-hour-day – for personnel connected with sealed sources of the ionizing radiation (gamma-, X-ray), also for morbid anatomists, prosectors, forensic medical experts, anatomists;
- 5.5-hour-day – for doctors of the tuberculosis, psycho-neurological centers, physiotherapeutists, dentists;
- 6-hour-day – at the infectious, tuberculosis, psychiatric, narcological, balneal, radon, laboratory departments.
The leading position in the system of medical
personnel health care is occupied by preventive and periodical medical
examinations, regulated by the Order of the former USSR Ministry of Public
Health (MPH) №
555 from 29.09.1989 and by the Order of Ministry of Public Health of
Issues of the medical personnel labour protection
are also implied by the “Law on labour protection of
Hygienic features of the working conditions and state of health of the doctors of surgical specialities.
Surgical specialities are: the general surgery, thoracal surgery, urinology traumathology and orthopedics, neurosurgery, obstetrics and gynecology, ophthalmology, oncology, facial surgery, surgical odontology, reanimation and anesthesiology. Except for enumerated, to surgical specialities referred anatomy, pathological anatomy, forensic medicine, surgical dermatology and other.
The professional feature of activity of the surgeons is multicomponent character of their working process. Except doing operations, as main activity of the doctors of a surgical profile, the considerable endurance of operating time is spent for inspecting patients, diagnostic, postoperative routines, morning conferences, planning how to do operations, filling in documentation (case history, protocols of operations), talking with the relatives of the patients, for the manager of departaments, hospitals - administrative duties, and so on.
Operational loading of the doctors of a surgical profile, by countings of the explorers, compound: in communal surgery – more than 150 operations for one year, more than 3 for one week; in otholaryngology, accordingly, - more than 170 and to 4; in an obstetrics and gyneacology - 370 and 7 (including abortions, abrasions - 230 and 5). With improvement of professional skill of the surgeon increase both amount, and complication of operations. Operational, rentgenodiagnostical and reanimational loading increase also at daily duties of the emergency.
By physiological feature of work activity of the surgeon in operational is obliged working pose, with static stress of the muscle system. Is established, that 37,6 % of all period of the operation a trunk of the surgeon pitched forward and 27 % - with additional rotation in one or other side, and only 26 % of time its trunk is in vertical position.The blood pressure in legs is increased in 2 times, in the field of a basin - on 50 %. Takes place lack of bloodsupply of brain. From here - headaches,
The working area of the surgeon, occupies up to
In the summer temperature of air
in operation room can reach
At conducting operations in conditions of hyperbaric oxigenation the surgeons and their helpers will experience the effect of warming microclimate, heightened atmospheric pressure and heightened infiltration into an organism of azote. The pressure in hyperbaric operational room reaches З and more atmospheres, that is considered predrug, in relation to azote. But the poor cubage in an barocamera, sometimes necessity of pressure increase up to 7-8 atmospheres, can condition of nitrogen narcosis for terms of operational team. The unfavorable operating constructs also process of a compression and, in particular, decompressions. Under operating of azote for terms of operational crew occur euphoria, the behavior (groundless laughter, slowing-down of motive reactings, decrease of attention, clearness of manipulations) is inflected.
The feature of a compression is
the rise of air temperature in barocamera from original, for example 20С, up to
27 and even 37 degrees. At a decompression, on the contrary, temperature is
slashed till 17-
The relative humidity at a compression is increased from 40-60% till 70-84%. At a radiodiagnosis, radiognostics, surgical manipulations in traumatology the doctors and their helpers will experience the influence of ionizing radiation.
It is necessary to mark, that on the participants of surgical crews, except the indicated physical factors, the toxiferous chemical agents affect. It, first of all, chemicals, which are used foringalation narcosis: dioxide of azote (Mine), Ftorotanum (fluotane, halotane), Aether ethanol, Chloroformium (three - chlorethanum), three-clorethilenum, cyclopropane, chlorethyl and other.
Concentration of Fortnum in air of operational room in different space from a mask of the patient compounds 80-216 mg/m3, nitrous oxide 234-1770 mg/m3', and their concentration is augmented proportionally to the duration of an operation, in particular at a semiopen circuit of breathing.
Concentration of inhalation narcotics in a zone of breathing of members of surgical crews depends on time of a surgical intervention (at the operation on lungs concentration to Ftorotanum reaches 1000-1500 mg/m3 ), cubage of operational room, activity of drugs.
From the point of view of hygiene of work the speed of elimination of drugs from an organism is also important. It was found, that diethyle Aether has rather quick output from an organism. The signs of Ftorotanum are discovered in exhaled air of the anaesthesiologist in 64 hours after operation. At once after the operation the concentration of Ftorotanum in exhaled air is equal 42мg/м3. It is considered, that takes place material cumulating of Ftorotanum at its repetitive inflow in an organism. Chloroformium is not stored in an organism, and the ethanol stays for two days.
During operations anaesthesiologists, surgeons, gyneacologists are in a state of a high mental and nervous - emotional stress. At continuous operations (3-6 hours) are degraded speed of oculomotorius reactings, the coordination of moves of a hand and fingers, slashed memory and attention, the brake processes in a CNS dominate.
The frequency of cardiac pumps of the surgeon, anaesthesiologist that are getting ready to the operation is higher on 5-10 pumps/min, reaching 88-110 pumps/min, increasing in accountable periods of the operation.
After operational interferences,
depending on their endurance, for the surgeons the diameter of legs is larger
Among diseases of the surgeons with a temporary disability on the main place comes the acute respiratory diseases, influenza, illnesses of organs of blood circulation, digestion, nervous system.
Among chronic diseases of the surgeons, gyneacologists, which are discovered by results of the deepened medical browses, the greatest specific weight is borrowed by the diseases of the system of blood circulation, by nervosisms, which are interlinked with high psycho-emotional and physical stress. In them most often the pains are localized in the field of heart, high arterial pressure, considerable changes of ECG, dissonances of the nervous system. The high case rate on gyneacological diseases, failure of pregnancy are discovered in the women - surgeons, which is interlinked, except of a psycho-emotional stress, with effect of anestetics and drugs.
The greatest amount of occupational diseases of
the medical workers recorded for the doctors, including surgeons, in age of the
highest working activity - 25-50 years. Behind frequency the greatest amount of
cases of occupational diseases of the medical workers beloongs to zymotic
illnesses, of which one most often are sick, except for infectionists and
ftiziatres, also surgeons, pathologists, stomatologists, otolaryngologists,
doctors - laboratory assistants. In
The considerable and continuous loading on a nervous - emotional and intellectual orb of the doctor - surgeon assists forming for him(it) of an idiopathic hypertensia, ischemic illness of heart, neurotic dissonances. A veheto-vascular dystonia, nervosism are discovered in the anaesthesiologists in 30 %.
The series of occupational diseases of the doctors is occupied by illnesses, which one are developed from a forced position of a body, stress of separate muscle groups; a radiculitis, osteochondrosis, discynesias, epicondylites - for the orthopedist - traumatologists.
Among reasons of progressing of occupational diseases for the doctors - surgeons select: a hypersensibility of an organism, absence or inefficiency of individual means of protection, non-compliance of the safety regulations, sanitary regulations, irregularity and deterioration of medical engineering, instruments, rigging.
Among diseases, which one has reduced in physical inability, 60 % are necessary on destiny of illnesses of chemical ethyology, 20 % - on illnesses conditioned by the biological factors, and till 10 % - on illnesses aroused by the physical factors and an overstrain of organs and systems.
As a result of originating professional disease the doctors were forced to inflect a place of operation through illnesses of chemical ethyology in 80 % of cases, through illnesses aroused by the biological factors in 11 % of cases and in 9 % through a functional overstrain.
Hygienic features of the working conditions and state of health of the doctors of a therapeutic profile.
To specialities of a therapeutic profile are referred: therapy with its derivation (gastroenterology, pulmonology, cardiology), phthisiology, zymotic illnesses, dermatovenerology, neurology, psychiatry, pedonosology, emergency.
From the point of view of features of operation and influencing of the unfavorable factors on the doctors of the enumerated specialities it is necessary to arrange on polyclinical, with a local principle of service ill, and on working in a hospital.
Among unfavorable psycho-emotional factors, the influencings will experience one of the divisionals theraputists, the carrying role belongs to excessive physical loading, which one depends on a season of year (amount of calls), sizes of a medical lease, such as building (one – multistore building, availability or absence of lifts).
Besides the divisionals theraputists and pediatrists, ER doctors, doctors - psychiatrists, the neuropathologists score constant psycho-emotional stress. It is conditioned by gravity of illness of the patients, complication of diagnostic, boundedness of possibilities of the doctor to help ill, feature of contacts of the doctor with ill and their with close.
The particular unfavorable operating on the doctors of a therapeutic profile is done by modern facilitiess of a hardware of medical entities - X-ray equipments, source of a radoactive radiation, electronic, ultrahigh-frequency, superhigh-frequency, ultrasonics, laser sets, source of ultraviolet radiation, chemical factors - pharmacological drugs, which one operate on medical staff by the way of solutions, gases, vapors and aerosolums.
For the doctors of leprosoriums, infectionists, dermato-venerologists, helmintologists, laboratory assistants antiplague, bacteriological, virologic, helmintological labs, desinfectors, epidemiologists particular professional unfavorable factors – exciters of the applicable zymotic diseases.
Among diseases of the doctors - theraputists with a temporary disability on the main place the acute respiratory diseases, influenza, illnesses of organs of blood circulation, digestion, nervous system. Thus the doctors - theraputists are sick considerably frequently and lengthy in matching with the doctors - surgeons, which work in a hospital (accordingly 103,4 cases and 128 dawned and 48,4 cases and 76,9 dawned disabilities on 100 working).
In pattern of chronic diseases trough theraputists the main rank places occupied by illnesses of digestion organs - (chronic cholecystitis, gastrityes, peptic ulcer of a stomach, duodenum), illness of the nervous system and sense organs. Are then routed: an ischias, radiculites conditioned by often variation of stay in building and outdoor at service or at home. It is necessary to note, that the considerable proportion of the doctors are engaged in services of the colleagues without the applicable decor of disease in medical documents. This feature essentially influences quality and endurance of treatment, entirety of the registration and, accordingly on an index of a case rate, that is why officially, of taking medical advices up to 600 cases on 1000 working, and on retrospective interrogation - up to 1500 on 1000 register.
To occupational diseases of the doctors of a therapeutic profile belong:
- The zymotic and stray diseases, homogeneous with theme, ill on which one are handled by the doctor, medical sister, laboratory assistant, desinfectors, (lepra, tuberculosis, plague, cholera, malignant anthrax, rabies, brucellosis, helminthiases etc.);
- The diseases, which one can arise at service of sources of ionizing radiation - X-ray, gamma - therapeutic vehicles and installations, at the robot with opened radionuclides (acute, chronic radial illness, leukoses, radial cataract, carcinoma cutaneum, hyperceratosis, papillomas, dermatitises, eczema, toxicodermias, melanodermias etc.);
- The diseases, which are caused by service of physiotherapeutic rigging - oscillators a UHF, UV, hydrosulphuric, radon cabinets т of separations engine driven laundries, autoclave installations, etc. (radioundular illness, photo-ophthalmia, traumas, casualties);
- The diseases, which are caused by operation with medicines, drug, disinfectants, other chemical combinations (acute and chronic poisonings, medicamental allergy, dermatoses etc.);
- The diseases, which one are developed at continuous immediate service mentally ill - professional psychoneurosis),
- Disease conditioned by considerable constant psycho-emotional stress (an idiopathic hypertensia, stenocardia with their complications).
Hygienic features of the working conditions and state health of the doctors - stomatologists.
Stomatological of a speciality are divided on a therapeutic odontology. A surgical odontology, facial cosmetic surgery, etc.
By one of main professional unfavorables for the doctor - stomatologist is a forced position of a body, which one is tracked by static stress of separate muscle systems. Depending on a construction of stomatological seat for the patient the stomatologist works standing or sitting.
At usage of seats and instrumentation of vertical constructions the doctor - stomatologist works standing rakish trunks 34 % of operating time. At usage of seats of a horizontal construction - sitting rakish and bending of a backbone in the side of the patient 75 % of operating time, and with a strong tilt and bending of a backbone - 22 % of operating time.
The muscle loading of the stomatologists by operation in a pose costing increases in 1,6 times, and rakish trunks - almost in 10 times. By operation in a pose sitting rakish trunks the muscle loading is augmented in 4 times.
Operation with minor defects in dents, their restricted accessibility to examining predetermine a stress of the visual evaluator and excessive convergence of an eye owing to nearing an organ of vision to plant of distinguishing.
From among the essential physical unfavorable factors for the doctors - stomatologists there is a noise from operation of a drill, compressors, sucktions. In particular dangerous is local chattering from operation of a drill, which one is transmitted to arms of the stomatologist.
The applying of photopolymeric valves of local lighting predetermines influencing on the doctor of powerful visible and uv radiation, and usage of polymeric materials and know-hows is tracked inflow in a zone of breathing of toxiferous matters of a miscellaneous genesis.
The operation with mercurial amalgams is tracked by influencing on medical staff of vapors of metallical Hydrargyrum.
One of most relevant professional unfavorable for the doctor - stomatologist is hazard of a taint from the patient with diseases of the upper respiratory paths, which one flow past in mild, defaced, atypic to the shape, or are in a stage of incubation. Besides the potential hazard of originating of zymotic disease exists at implementation of manipulations, conducted with contact to a saliva, tissue an ash, blood of the ill or infected faces.
Medical examination of a state of health of the doctors - stomatologists has shown, that at continuous one way loading are expanded a tendon, owing to the joints, and bones are misplaced. The offset in a knee joint results in variations in coxofemoral, talocrural joints, progressing flat stops. The resistant variations of a backbone are step-by-step developed, there is a scoliosis, kyphosis, lordosis in cervical, thoracal, lumbar departments. Doctor working in a standing pose rakish trunks frequently results in disease of a gall bladder. The deduction od bile is degraded, the gallstones are gained, the internal organs are cramped, diaphragmal breathing becomes complicated.
By the studies of the german scientist Shebil (1971), in 70 % of the young specialists - stomatologists in 6-30 months after beginning of their activity there are this or that signs, which one testify to disease in them of a sceletal musculation.
The work of the stomatologist in a sitting pose near horizontal stomatological seat with deflection of a trunk from a vertical on 25-30 degrees with homing of a shoulder girdle on 28 degrees stagnation of a blood in organs of abdominal cavity, basin, progressing of a cholecystitis, less often than peptic ulcer, radiculitis, ischias. Thus take place (as well as for the doctors of a surgical profile) padding gains on upheaval and holding of arms in suspended position, which one assists even greater and is quick in occurring fatigue. Forced working outside of and the static stress of a locomotorium will call pains in a backbone, neuralgia in a shoulder girdle, necks, hemostasis in legs, platipedia, osteochondrosis.
Necessity of precise, thin manipulations during medical operation, stereotyped moves, statico-dynamic stress of muscles of fingers, hand
Arms, shoulder girdle, the holding of instruments not by gains of a fist, and fingers of arms (in a position – holding of a pencil), but with considerable physical gains, will call a hypertrophy of separate groups of muscles. Thus are so-called professional pains. Step-by-step accrueing, result to spastic contraction of all group of muscles, down to shoulder girdles.
Owing to operating local chattering from a drill occur of tag of percussive illness: tiredness, cramp and pain in fingers, feel of a numbness of arms, losses tactile and thermoesthesia.
As a result of a constant stamping of the hand lever metallical instruments on the same place can be developed contracture of Duipuirtene.
The stress of the visual evaluator can result in to a spastic stricture of accommodation and originating of a so-called artificial myopia, and the operation with photopolymeric valves can invoke a photo-ophthalmia, combustions of a cornea, clouding of crystalline. In this connection the characteristic complains on tiredness of vision, feel of “sand in eyes ", discomfort.
The operation with mercurial amalgams can be the reason originatings for the doctors - stomatologists, medical sisters, tooth techniques of micromercuralism.
The greater 25 zymotic diseases, including HIV, prion illness, hepatitises B and C passed through a saliva, tissue an opened wound. The often placer mining of arms by a sweeper can assist progressing micogenues eczemas, disgydrosis, epidermofitias.
Measures on environmental sanitation of the working conditions of the medical workers.
By one of main conditions of environmental sanitation and protection of operation of the medical workers, the creation of optimal conditions for effective conducting of the medical process is plane-architectual solution of treatment-and-prophylactic entity. The building of major hospitals (on 600-1000 beds) significally meliorates the working conditions of the medical workers. This building is carried out presently according to building norms. These norms stipulate the enumeration of indispensable buildings, according to assigning of hospital, separation, two corridor system, oversizes of main functional buildings, operational, minor surgery, procedural, manipulating. For the doctors foreseen " rooms of psychological discharging ", specialized gymnastics, room of personal hygiene of staff.
So, at budgeting surgical separations the
insulated building of two surgery blocks - aseptic and septic, with airlock
passes to department is stipulated. In a surgery block the gateway servers,
supplementary puttings are guessed a floor broker, preoperational, sterylazing,
narcosis, hardware, putting for a synthetic circulation of blood, putting for
staff. The surgery block should be endured in the separate body, with the
covered transferrings to the major body, to separation. Should be isolated
clean and purulent Minor surgery. The floor space of a floor broker - at the
rate of 36-
The acceptance separation of the surgical departament, as against other, should be provided with rentgenodiagnostical facilitiess, operational (for immediate surgeries behind biotic indexs), antiseptic rigging and facilitiess, etc.
Designed separate special building both sanitary regulations and rules for tubercular, infectious diseases hospitals and separations, rentgenological cabinets, separations, labs, clinical-diagnostic, bacteriological, helmintological, virologic labs, hydrosulphuric, radon departments, psychiatric, antileprosoric hospitals, protesing labs, disinfectant servers engine driven laundries, boiler-houses, which one are esteemed in the applicable partitions of guidings from municipal hygiene.
The relevant value in environmental sanitation of the working conditions of the medical workers has rational arranging of medical furniture and machineries in the medical cabinet.
The sanitary regulations and norms - stipulate creations of optimal microclimatic conditions in separate functional buildings of hospital entities, ventilating system, conditioning of air, natural and synthetic lighting, sanitary - hardware (cold and ardent water facilities, communal and special water drain).
It is necessary to conduct systematic laboratory check of concentration of anestetics in operational with the purpose of debarment overflow them MAC: for a Aether - 300 mg/m3, Ftorotanum - 20 mg/m3, inhalanum - 200 mg/m3, Chloroformium - 5 mg/m3, cloraethilum - 50 mg/m3, Trilenum - 10 mg/m3.
At usage simultaneously several anestetics the total of ratioes of their actual concentrations to them GDK should not exceed unities.
However, the most effective preventive action against toxiferous operating of anaestetics on members of operational crew is transferring to intravenous narcosis and spinecord anaesthesia.
Concerning other chemical combinations, with which one the medical staff can work, first of all it is necessary to determine, that it is necessary to conduct operations with medicines, disinfectants, acids, meadows in fume hoods, for the patients - in inhalation cabs. Besides it is necessary to utillize individual means of protection - rubber gloves, defensive oculars, masks, respirators, film skirts and even an overalls. For arms with the purpose the preventing to progressing of allergic reactings is necessary to utillize defensive creams. With same purpose it is necessary to prefer tablet medicines.
Designed marginal levels of bacterial air pollution of hospital buildings. So, in operational up to 500 colony / м3 air to the operation, 1000 colonies / м3 after the operation is enabled; in chambers of reanimation and intensive care - not the greater 750 staffs / м3, and pathogenous of a staphylococcus -к 4-х/м3. In genitive halls - up to 2000 colony / m3, and staphylococcuses and streptococcuses - not greater 24-х/м3.
For support of purity air of hospital buildings, except for natural and the forced ventilation, will do air conditionaires ВОПР-09, ВОПР-1,5, which resolve to reduce dustivity and bacterial contamination of air during 15 minutes at 7-10 of time. In surgery blocks, minor syrgery, children's chambers, genitive halls rather effective uv radiation by germicidal lamps ЛБ-30, БУВ-ЗОП etc., straight light in absence of the people.
The uv radiation of hospital buildings in presence of the people, except for germicidal effect, assists a heightening of a resistance of an organism of the medical workers (as well as patients) to zymotic and other illnesses, do general stimulating, D-vitaminsynthesizing effect, pigmentsynthesizing effect. Nevertheless in this case there can be a hazard of a photo-ophthalmia, if the vision hits in a zone forward(straight) uv-radiation.
PHYSICAL BASICS OF RADIATION HYGIENE
Radiation hygiene is a branch of hygienic science and sanitary practice, purpose of which is to provide safety for people working with sources of ionizing radiation and for population as a whole.
Tasks of radiation hygiene include:
- sanitary legislation in radiation factor sphere;
- preventive and regular sanitary control at objects, that use sources of ionizing radiation;
- hygiene and protection of personnel working with sources of ionizing radiation and personnel working in adjacent premises and on the territory of supervised zones;
- inspection of radiation level of objects of the environment (atmospheric air, air of work zone, water of reservoirs, drinking water, food substances, soil and others);
- inspection of collection, storage, removal and neutralization of radioactive waste, their entombment etc.
Radioactivity is spontaneous transformation of atoms’ nuclei of chemical elements with change of their chemical nature or energy state of nucleus, accompanied by nuclear radiation.
Radioactive nuclide is radioactive atom with certain mass number and charge (atomic number).
Radioactive isotopes are radioactive atoms with equal charge (atomic number) and different mass numbers i.e. with equal number of protons and different number of neutrons in nucleus.
Types of nuclear transformation:
α-decay is typical for heavy (with great mass number) elements and consists in takeoff of α-particle (helium nucleus by its nature, consisting of 2 protons and 2 neurons) from the nucleus of atom, and a nucleus of new chemical element with mass number, smaller by 4 and charge, smaller by 2 appears as a result:
When losing α-particle, the nucleus of atom finds itself in excited state with excess of energy that evolves in the form of γ-radiation, i.e. α-decay is always accompanied by γ-radiation.
β- electron decay is a process when electron takes off from nucleus of atom (from one of neutrons) and, as a result, this neutron transforms into proton and a new element with the same mass number and charge, bigger by 1 is generated:
where ν- is neutrino.
The nucleus, excited after losing electron radiates γ-quantum in all cases.
Beta-plus decay is process when positron takes off from the nucleus of atom (one of protons) and, as a result, proton transforms into neutron and a new chemical element with the same mass number and charge, smaller by 1 is generated:
Electron K-capture is when nucleus (one of protons) captures an electron from the nearest K-orbit and, as a result, this proton transforms into neutron and nucleus of new chemical element with the same mass number and charge, smaller by 1 is generated:
Electrons migrate to the vacant place at the K-orbit (consecutively from other orbits) and freed energy is irradiated as a typical roentgen radiation.
Spontaneous fission of the nucleus is typical for heavy transuranous elements, where ratio of neutrons and protons is more than 1.6. As a result of it nuclei of two new elements are generated, where ratio n:p is closer to 1 and «superfluous» neutrons leave atoms in form of a neutron radiation:
In that way in a qualitative sense nuclear changes are characterized by: kind of decay, kind of radiation, half-life period – time, during which half of initial amount of atoms are decayed. (According to the law of radioactive decay, the amount of atoms N that decay during time t is proportional to initial amount of atoms): N=N0·e-λt.
From hygienic and choice of method of radioactive waste decontamination points of view, all radioactive nuclides are divided into short-living (T1/2 < 15 days) and long-living (T1/2 > 15 days): the short-living are aged in gravity trap until radioactivity decreases, and after that are disposed into sewerage or are removed, and long-living are removed and buried in special mortuary.
Quantitative measure of radioactive decay is activity (Q) - the amount of decays of atoms during unit time.
Unit of activity in System International (SI) is Becquerel (Bq) - one decay per second (s-1). Because this unit is very small, kiloBecquerel (kBq) and megaBecquerel (MBq) are in use.
Curie (Cu) is off-system unit of activity - it is the activity of 1g of chemically pure radium and it is equal to 3.7·1010 Bq (decays per second). Vice versa this unit is very big, that is why milliCurie (mCu), microCurie (μCu), picoCurie (pcCu) are in use.
radioactive nuclides, for which γ-radiation is typical, activity is
calculated through gamma-equivalent - a ratio of γ-radiation of given
radioactive nuclide to γ-radiation of radium. Gamma coefficient of radium
is 8.4 R/hour - it is the dose rate, generated by 1 mg of radium at the
of radium (mg-equ. Ra) is activity unit of radioactive nuclide,
γ-radiation of which is equivalent (equal in value) to γ-radiation of
1 mg of Ra at the distance
In a qualitative sense ionizing radiations are characterized by:
- kind of radiation: - corpuscular (α-, β-, n), electromagnetic (γ-, roentgen: typical at K-capture, deceleration – in roentgen tube).
- energy of radiation, that is measured in Joule in SI. (This is energy that is necessary for heating of 1 dm3 of distilled water by 1 C°. Off-system unit is electron volt (eV) - energy that electron gets in electrostatic field with difference of potentials equal to 1 V. As this unit is very small, derivations of this unit, such as kilo electron volt (keV), mega electron volts (MeV) are in use.
- penetrating power (path length) - the distance, which radiation passes in the medium, it interacts with (in m, cm, mm, μm).
- ionizing power: total – amount of couples of ions that are formed along the whole path length of particle or quantum; linear density of ionization – amount of couples of ions per unit of path length.
Qualitative characteristics of ionizing radiation are doses (D).
1. Absorbed dose – quantity of energy of ionizing radiation that was absorbed by unit of mass of irradiated medium. Unit of measurement of absorbed dose in SI is Gray (Gy).
is absorbed dose of radiation that is equal to energy of 1 Joule absorbed in
Absorbed dose in the air is measure of quantity of ionizing radiation that interacts with the air. It is measured in Joule/kg of air mass i.e. in Gy. The old notion of absorbed dose in the air is exposure dose that is bulk density of the air ionization. The unit of exposure dose is roentgen (R).
is dose of roentgen or γ-radiation that makes 2.08·109 couples
of ions per 1 cm3 of the standard dry air (0 C°,
760 mm Hg, mass
2. Absorbed dose rate in the air (ADR) is increase of dose per unit of time or radiation level. It is measured: in SI – Gy/hour; off-system unit (old) unit is Roentgen per hour (R/hour), milliRoentgen per hour (mR/hour), microRoentgen per second (μR/sec). Because all dosimetric devices that are in use in Ukraine at present are calibrated in those units, results of measurements must be re-calculated in SI (Gray-, milli-, micro-, nanoGray/hour): 1 mR/hour = 8.73 μGy/hour = 6.46 μSv/hour.
3. Equivalent dose (H) is dose of any kind of ionizing radiation that causes the same biological effect as standard (sample) roentgen radiation with energy 200 KeV.
Radiation weighting factor (WR) is used for calculation of equivalent dose, it is the coefficient, that takes into account the relative biological effect of different kinds of ionizing radiation. For roentgen, gamma-, beta-radiation of different energy it is equal to 1, for α-particles and heavy nuclei it is equal to 20, for neutrons with energy <10 KeV – 5; 10-100 KeV – 10; 100 KeV-2 MeV – 20; 2-20 MeV – 10; >20 MeV – 5.
H = D ×WR
Unit of equivalent dose is Sievert (Sv), it is a dose of any kind of ionizing radiation that makes the same biological effect as 1 Gray of standard roentgen radiation (with energy 200 KeV). Derived quantities such as millisievert (mSv), microsievert (μSv) are also in use in practice.
Effective dose is the sum of equivalent doses that were received by separate organs and tissues during non-uniform irradiation of the organism, multiplied by tissue weighting factor: for gonads – 0.20; for red bone marrow, lungs, stomach – 0.12; for other organs and tissues – 0.05.
Unit of measurement of effective doses is Sievert also.
Population equivalent and population effective doses are sums of appropriate individual does of separate contingents of population (personnel of atomic industry corporations, atomic energetics, population living in borders of controlled zones) that are measured in man-Sievert and are used for prognostics of stochastic (probable) effects of irradiation – leucosis and other malignant tumors.
Principles of providing of radiation safety for personal in radiological deaprtments of hospitals and for population at the use of ionizing radiations in medical establishments, in particular, in the roentgenologic separation (cabinet) of stomatology policlinic
Quantities and units of radiation dose
Interactions of X-ray and gamma photons always set electrons in motion with sufficient energy to ionize and excite atoms and molecules. An electron therefore deposits energy in its wake. Around 10-100 ionizations/ m caused by an electron are generated at diagnostic X-ray energies (approximately 33 eV/ion pair). The concept of linear energy transfer, LET (unit keV/ m) can be used to describe this phenomenon together with the concept quality factor Q, explained later. In addition, part of the energy of the electron is absorbed by secondary electrons, so-called delta particles; they in turn have sufficient energy to cause new ionizations.
Exposure implies that ions are generated in air as a consequence of the passage of radiation. Ions can be measured with an ionization chamber, which is an air space between two conducting plates coupled to the positive and negative poles of a voltage source. The exposure = the number of ions with negative (or positive) charges divided by the mass of air in the ionization chamber. The SI-unit is C/kg (C = coulomb). The older unit is roentgen R = 2,58 10-4 C/kg.
This quantity is the energy per unit mass, which matter has absorbed from radiation. The SI-unit is the gray Gy = J/kg (the old unit was rad = 0.01 Gy). At X-ray and isotope imaging energies (15-500 keV) one R exposure causes approximately 10 mGy (one rad) absorbed dose in all other tissues except in bone, where the absorbed dose at low energies (around 20 keV) reaches up to around 40 mGy.
When energy has been absorbed in tissue the biological effect varies depending on the organ in question, the type of radiation and energy, dose rate, exposure time etc. These are incorporated in the concept quality factor Q, by which the absorbed dose must be multiplied to get the equivalent dose. Its unit is sievert Sv = J/kg (= 100 rem, the old unit).
In X-ray and isotope imaging, Q is approximately 1, because X and gamma radiation deposit relatively small amounts of energy in tissue. Another concept, effective dose, describes the probability of damage to different organs with a weighting coefficient, which is high for radiation sensitive organs such as gonads, bone marrow, lungs, colon, breast etc. and small for other tissues, e.g. muscle. The sum of the weighting factors equals to 1.
From the foregoing it is clear that in diagnostic imaging, the units Gy and Sv, as well as R, rad and rem, have about the same numeric values, although the concepts have different meanings.
One useful concept in dosimetry is the rate, with which a given amount of radiation strikes tissues, for instance kerma rate and exposure rate mR/min, R/h etc. Activity (see the chapter Radioisotopes and radio pharmaceuticals) is also a concept which incorporates the function of time. Whether X-rays from an X-ray device or gamma radiation from radionuclides are discussed, the same concepts can be used to describe radiation phenomena and the biological effects of radiation.
Ionization and excitation result in fragmentation of molecular bonds with potentially harmful consequences to cell structure, metabolism and organ function. Injuries are divided into genetic and somatic ones. The former can appear in descendants after a long time has elapsed, and the latter may occur quickly (acute consequences) or after a considerable delay. In the peaceful usage of ionizing radiation acute toxicity does not occur.
A distinction is also made between stochastic and non-stochastic effects of radiation. Stochastic implies that even a single "hit" of radiation to one cell or to a small cell group can cause a biological consequence. Damage may be either hereditary (in gonads) or carcinogenic (in tissue). There is no threshold, i.e. the extent of the damage does not depend on absorbed dose (cancer is contracted or not), although the probability of an adverse event increases with dose. This stochastic nature of radiation is therefore the basis of conservative radiation protection.
The non-stochastic effect of radiation has a definite threshold (normally different for every tissue and organ). These have been found from past experience, e.g. in cancer treatment with radiotherapy during this century. Diagnostic radiation examinations (where skin dose varies between 0.1 mSv and 0.1 Sv / examination) expose the patient to very small doses so the consequences of non-stochastic effects do not evolve. One clear exception is the dose to a fetus, particularly during the sensitive period of organogenesis. Therefore, the indications for pediatric examinations involving ionizing radiation must be examined particularly closely.
It is estimated that if 200 000-2 000 000 people get a dose of l mSv (the same as the background dose per year without radon) it is probable that one person will develop cancer. It is, however, impossible to separate so few cases from cancers caused by other factors, such as environmental toxins and unknown reasons etc.
Many other factors such as the type of radiation and energy, LET value, dose rate, time between exposures or fractionation of dose, different sensitivity of tissues for radiation, biological variations etc. have a significant effect on the likelihood of injury.
Because injuries from small doses can partly be stochastic the starting point of radiation protection is to avoid and reduce somatic and genetic doses to as low a level as possible (ALARA, As Low As Reasonably Achievable). The consequences of small doses given over long periods of time are partly unknown, and as the time for a carcinoma to appear can be decades, damages caused by low level radiation are often impossible to separate from diseases caused by other factors. On the other hand it is important to use sufficient radiation to achieve good quality images. These examinations, which are clinically indicated, must be performed with sufficient radiation to achieve an image of diagnostic value.
The dose can be measured or estimated at different depths in the patient, or in different parts of the environment. Terms like skin dose (or surface or entrance dose), depth dose, dose in patient's centre, exit dose (approximately the same as dose to the screen without a grid) and organ dose are fairly self-evident. Dose diminishes as the depth at which it is measured increases. In the diagnostic examination of the body only a 1/100-1/1000
part of the initial dose penetrates through. Dose decreases also without matter, even in air. Radiation intensity (as well as light intensity) decreases in inverse proportion to the square of the distance from the focus.
Fig. shows how skin dose and exit dose are changed with patient thickness when the exposure of film to a constant blackness (optical density) is made with an automatic exposure meter. In this case exit dose does not depend on thickness, because a screen-film combination always requires a certain amount of radiation.
Many features of X-ray devices and properties of patient tissues influence the dose needed for good image quality.
There are big differences in the properties of different imaging methods and in radiation detectors. Screen-film-combinations are always used in practise instead of film alone. Screen sensitivities vary from speed value 20 to 1600 (that of the reference screen-film-combination being 100), when the speed of the film alone has a value of about l. Consequently corresponding alterations can be found in patient doses.
The first rule in the radiation protection of personnel is to go outside the X-ray laboratory when a patient exposure is made. In fluoroscopic examinations one must work l) quickly, 2) with sufficient protective clothing, and 3) at an appropriate distance from radiation sources. These three measures are of primary importance in both X-ray and isotope work. The staff who are most likely to be exposed to radiation are those who work with fluoroscopic devices (radiologists, surgeons etc.), nurses who hold small children or non-cooperative patients, as well as staff working with the nuclear medicine imaging of patients.
National and international radiation legislation and recommendations are universally in use. According to these regulations, for instance, examination rooms, devices and working conditions must be adapted so that doses are diminished to as low a level as possible and that the quality of images and examinations attains the highest possible level. The most recent ICRP recommendation (publication 60, 1991) puts the maximum dose level of 20 mSv per one year to the whole body of personnel. This value is 40% of the earlier maximum limit, which shows the increasingly conservative attitude in radiation protection.
One should remember that the dose to personnel from scattered radiation is 100-1000 times smaller than the dose in the entrance field on the patient's skin. Therefore it is essential for the radiation worker to avoid putting his hands in the primary radiation field (use lead gloves). The patient's body can also serve as good protection, if one can place oneself in such a position that one does not directly see the entrance field of radiation.
Radiation Detection and Measurements
Two types of methods are used to measure
external dose. One consists of using instruments such as survey meters, surface
contamination meters, and neutron detectors. These instruments comprise the gas
filled detectors (Geiger-Müller or proportional detectors), the
scintillation detectors, and some special detectors for neutrons.
When performing monitoring the following actions are required:
1. Check first if the right method (direct or indirect monitoring) is required for the type of radionuclide used.
2. Check if the instrument has been calibrated less that a year ago (check the sticker on your instrument) ensure that the battery and HV (when there are available) indicators are in the correct range.
3. Measure the background before reading the values in the work area.
4. Subtract the background after taking readings in the work area.
5. With the remaining number and the instrument's efficiency for that particular radionuclide (see sticker), estimate the level of contamination.
6. Take the necessary actions to reduce the contamination below the set limits.
The second method for measuring external dose is personal dosimetry.
This consists of whole body Thermoluminescent Dosimeters (TLDs), extremity TLDs, and neutron dosimeters. The TLDs are contracted with a licensed company and the dose is measured every three months. The results are reported to the UTRPS and to the Health Canada. After checking each report and comparing it to the administrative action levels, the UTRPS sends the results to the workers. These dose measurement results are strictly confidential.
With respect to internal dosimetry, U of T performs two types of bioassays. A baseline measurement for each person starting the usage of sufficiently large quantities of radioactive Iodine, Tritium, or other radionuclides is performed before starting the work. This measurement is important as a reference, but will not be used as a substitute for background of our measurements.
The first type of bioassay is dedicated to Iodine users (I-131 and I-125) and consists of measuring the concentration of radioactive Iodine in the thyroid. This measurement must be performed shortly after the time of use, but not later than 4 days post-usage.
The second type of bioassay is urinalysis. Because most radionuclides used at U of T can be detected in body fluids, this is a very good method to check for possible ingestion or inhalation of various radionuclides. Urinalysis is performed shortly after usage of radionuclides, but no later than 4 days post-usage. If radionuclides are discovered in someone's body, an estimate of the inhaled or ingested quantity is performed, and compared with the annual Allowable Limit on Intake (ALI) for that particular radionuclide. Immediate action is taken to stop the intake by analysing the work practices, changing the work procedures, etc.
As stated earlier, the possession, storage, use and disposal of radioactive materials is highly regulated at the international, federal, provincial, municipal, and local (U of T) levels.
U of T Policy, Standards and Procedures for Radiation Safety
A number of radiation safety policies have been developed and adopted by the UTRPA.
Training is considered the first important step in radiation safety. All radioisotope users must have either U of T radiation safety training or equivalent, which must be recognised by the RPS. One-hour administrative training is required for all users, including those with equivalent radiation training. When applying for a new user's TLD, the permit holder must sign the application and send it to the RPS. A Radiation Safety Officer will check if the new radioisotope user was trained or will contact the new user to arrange for radiation training. At the end of the course, the applicant must pass a written examination. Upon successful completion of the course and examination, a Radiation Safety Officer will administer a short oral quiz in the laboratory where the radioisotope work is being conducted, before providing a radiation course certificate.
A comprehensive set of procedures and standards for radiation safety has been developed and maintained by the RPS. There are procedures for ordering, receiving and transferring of radioactive materials , both from outside and within U of T. Special procedures have also been developed for the disposal of radioactive materials .
Procedures for working with radioactive materials are developed for each particular use by the permit holder. These are audited by the RPS. Special evaluation of the procedures will be performed:
- When an external exposure above the administrative action limit is recorded
- When an intake is discovered during bioassay
- In the case of a self-declared pregnant worker
Procedures and checklists are established for commissioning a new radioactive laboratory. Laboratories are classified as basic, intermediate or high depending on the amount and type of radioactive materials to be used. During commissioning, radiation signs and labels are posted inside the laboratory. Depending on the type of laboratory, special security may be required. Radioactive materials should always be kept locked to prevent access by unauthorised persons. Strict record keeping of received, stored, used, and disposed radioactive materials , as well as contamination monitoring , is also required. These records must be available for the last three years of radioactive use in the laboratory.
To prevent any accidental ingestion of radioactive materials, food and beverages are strictly prohibited inside the radioactive laboratories. After performing experiments with radioactive materials, contamination monitoring must be performed by each user. Results of the monitoring must be recorded and made available to the RPS Radiation Safety Officer and/or CNSC inspectors.
A special procedure is required for checking sealed sources with activities greater than 1mCi (37 MBq). Also, decommissioning of radioactive labs or instruments with radioactive sources is performed according to special procedures.
U of T Radiation Emergency Procedures
During the course of normal operations with radioactive materials, a spill can occur resulting in contamination of personnel or lab equipment and areas. Also, external irradiation can be encountered from a strong gamma or neutron source left unshielded. Appropriate actions must be taken during such incidents to prevent unnecessary doses to personnel and further spread of contamination.
In case of serious injury, medical attention takes precedence over radiological or other concerns. Dial 416-978-2374 or the Campus Police immediately and inform U of T RPS or Campus Police about the incident, injury, and that radioactive materials are involved. Alert everyone in the area and take all reasonable precautions to limit the spread of radioactive contamination or further exposures. Never risk external or internal contamination to save equipment or an experiment.
In case of a radioactive spill, contact RPS immediately if internal irradiation (inhalation/ingestion of radioactive material) is suspected, if excessive external dose is suspected, if significant contamination of personnel is suspected, or in the case of contamination of large areas. In this case, besides the general emergency procedures listed above follow the radioactive spill instructions.
In any clean-up of a radioactive spill, always clean the area until measurements indicate that the contamination is below the contamination limits before removing radioactive warning signs. If there is any questions of the effectiveness of the spill clean up, contact the RPS or U of T Campus Police.
In case of an emergency involving strong gamma or neutron sources, evacuate the area and contact the U of T RPS or Campus Police. Determine the limits of the area with dose rates above 2.5 mSv/hr (0.25 mrem/hr). Restrict access to that area by using radioactive signs and/or tape, closing the doors, etc. Guard the area until RPS/U of T Police representatives arrive.
In case of emergencies involving radiation-producing machines (X-ray), turn off the machine and unplug or shut off the circuit breaker for the machine. In the case of injury to personnel, call 416-978-2374 or the U of T Campus Police, notify the laboratory supervisor, and record all information about the incident (eg. operating voltage and current, exposure time, distance from radiation source).
Radiation protection and patient dose
Both ionizing and non-ionizing radiation as well as ultrasound are used in medical imaging methods. Somatic (occurs in own tissues) or genetic (in descendants) damage in patients or personnel are always a risk of examinations which employ ionizing radiation. Photons of non-ionization radiation (radio wave radiation in a strong magnetic field), as well as ultrasound, carry insufficient energy to cause injuries at diagnostic energy levels. Consequently, radiation protection is needed in practice only in X-ray and isotope examinations and in radiotherapy.
There are many factors which influence image quality. By increasing the amount of radiation (and patient dose) image quality can be increased to a certain level, but simultaneously several factors in the imaging chain can diminish quality. The quality control of imaging methods should be arranged such that high image quality with a dose as low as reasonably achievable (ALARA) is maintained.
The purpose of radiation protection is to eliminate the acute toxicity of radiation exposure and diminish the somatic and genetic risks to patients and personnel. It is useful to remember that the natural background radiation in the Nordic Countries varies between 3-6 mSv (300-600 mrem) per year. There is radiation coming from space, soil (radon gas is a very considerable source of radiation) and construction materials, as well as from our own tissues. Background radiation can vary depending on residential area, life style, etc. This value of 3-6 mSv is the same order as the skin dose from an X-ray image of the body.
The occurrence of particular health effects from exposure to ionizing radiation is a complicated function of numerous factors including:
- Type of radiation involved. All kinds of ionizing radiation can produce health effects. The main difference in the ability of alpha and beta particles and Gamma and X-rays to cause health effects is the amount of energy they have. Their energy determines how far they can penetrate into tissue and how much energy they are able to transmit directly or indirectly to tissues.
- Size of dose received. The higher the dose of radiation received, the higher the likelihood of health effects.
- Rate the dose is received. Tissue can receive larger dosages over a period of time. If the dosage occurs over a number of days or weeks, the results are often not as serious if a similar dose was received in a matter of minutes.
- Part of the body exposed. Extremities such as the hands or feet are able to receive a greater amount of radiation with less resulting damage than blood forming organs housed in the torso. See radiosensitivity page for more information.
- The age of the individual. As a person ages, cell division slows and the body is less sensitive to the effects of ionizing radiation. Once cell division has slowed, the effects of radiation are somewhat less damaging than when cells were rapidly dividing.
- Biological differences. Some individuals are more sensitive to the effects of radiation than others. Studies have not been able to conclusively determine the differences.
The effects of ionizing radiation upon humans are often broadly classified as being either stochastic or nonstochastic. These two terms are discussed more in the next few pages.
Stochastic effects are those that occur by chance and consist primarily of cancer and genetic effects. Stochastic effects often show up years after exposure. As the dose to an individual increases, the probability that cancer or a genetic effect will occur also increases. However, at no time, even for high doses, is it certain that cancer or genetic damage will result. Similarly, for stochastic effects, there is no threshold dose below which it is relatively certain that an adverse effect cannot occur. In addition, because stochastic effects can occur in individuals that have not been exposed to radiation above background levels, it can never be determined for certain that an occurrence of cancer or genetic damage was due to a specific exposure.
it cannot be determined conclusively, it often possible to estimate the
probability that radiation exposure will cause a stochastic effect. As
mentioned previously, it is estimated that the probability of having a cancer
Radiation-induced hereditary effects have not been observed in human populations, yet they have been demonstrated in animals. If the germ cells that are present in the ovaries and testes and are responsible for reproduction were modified by radiation, hereditary effects could occur in the progeny of the individual. Exposure of the embryo or fetus to ionizing radiation could increase the risk of leukemia in infants and, during certain periods in early pregnancy, may lead to mental retardation and congenital malformations if the amount of radiation is sufficiently high
Cancer is any malignant growth or tumor caused by abnormal and uncontrolled cell division. Cancer may spread to other parts of the body through the lymphatic system or the blood stream. The carcinogenic effects of doses of 100 rads (1 Gy) or more of gamma radiation delivered at high dose rates are well documented, consistent and definitive.
Although any organ or tissue may develop a tumor after overexposure to radiation, certain organs and tissues seem to be more sensitive in this respect than others. Radiation-induced cancer is observed most frequently in the hemopoietic system, in the thyroid, in the bone, and in the skin. In all these cases, the tumor induction time in man is relatively long - on the order of 5 to 20 years after exposure.
Carcinoma of the skin was the first type of malignancy that was
associated with exposure to x-rays. Early x-ray workers, including physicists
and physicians, had a much higher incidence of skin cancer than could be expected
from random occurrences of this disease. Well over 100 cases of radiation
induced skin cancer are documented in the literature. As early as
Leukemia is a cancer of the early blood-forming cells. Usually, the leukemia is a cancer of the white blood cells, but leukemia can involve other blood cell types as well. Leukemia starts in the bone marrow and then spreads to the blood. From there it can go to the lymph nodes, spleen, liver, central nervous system (the brain and spinal cord), testes (testicles), or other organs. Leukemia is among the most likely forms of malignancy resulting from overexposure to total body radiation. Chronic lymphocytic leukemia does not appear to be related to radiation exposure.
Radiologists and other physicians who used x-rays in their practice before strict health physics practices were common showed a significantly higher rate of leukemia than did their colleagues who did not use radiation. Among American radiologists, the doses associated with the increased rate of leukemia were on the order of 100 rads (1 Gy) per year. With the increased practice of health physics, the difference in leukemia rate between radiologists and other physicians has been continually decreasing.
Among the survivors of the nuclear bombings of
The questions regarding the leukemogenicity of low radiation doses and of the existence of a non-zero threshold dose for leukemia induction remain unanswered, and are the subject of controversy. On the basis of a few limited studies, it was inferred that as little as 1-5 rads (10-50 mGy) of x-rays could lead to leukemia. Other studies imply that a threshold dose for radiogenic leukemia is significantly higher. However, it is reasonable to infer that low level radiation at doses associated with most diagnostic x-ray procedures, with occupational exposure within the recommended limits, and with natural radiation is a very weak leukemogen, and that the attributive risk of leukemia from low level radiation is probably very small.
Genetic information necessary for the production and functioning of a new organism is contained in the chromosomes of the germ cells - the sperm and the ovum. The normal human somatic cell contains 46 of these chromosomes; mature sperm and ovum each carry 23 chromosomes. When an ovum is fertilized by a sperm, the resulting cell, called a zygote, contains a full complement of 46 chromosomes. During the 9-month gestation period, the fertilized egg, by successive cellular division and differentiation, develops into a new individual. In the course of the cellular divisions, the chromosomes are exactly duplicated, so that cells in the body contain the same genetic information. The units of information in the chromosomes are called genes. Each gene is an enormously complex macromolecule called deoxyribonucleic acid (DNA), in which the genetic information is coded according to the sequence of certain molecular and sub-assemblies called bases. The DNA molecule consists of two long chains in a spiral double helix. The two long intertwined strands are held together by the bases, which form cross-links between the long strands in the same manner as the treads in a step-ladder.
The genetic information can be altered by many different chemical and physical agents called mutagens, which disrupt the sequence of bases in a DNA molecule. If this information content of a somatic cell is scrambled, then its descendants may show some sort of an abnormality. If the information that is jumbled is in a germ cell that subsequently is fertilized, then the new individual may carry a genetic defect, or a mutation. Such a mutation is often called a point mutation, since it results from damage to one point on a gene. Most geneticists believe that the majority of such mutations in man are undesirable or harmful.
In addition to point mutations, genetic damage can arise through chromosomal aberrations. Certain chemical and physical agents can cause chromosomes to break. In most of these breaks, the fragments reunite, and the only result may be a point mutation at the site of the original break. In a small fraction of breaks, however, the broken pieces do not reunite. When this happens, one of the broken fragments may be lost when the cell divides, and the daughter cell does not receive the genetic information contained in the lost fragment. The other possibility following chromosomal breakage, especially if two or more chromosomes are broken, is the interchange of the fragments among the broken chromosomes, and the production of aberrant chromosomes. Cells with such aberrant chromosomes usually have impaired reproductive capacity as well as other abnormalities.
Studies suggest that the existence of a threshold dose for the genetic effects of radiation is unlikely. However, they also show that the genetic effects of radiation are inversely dependent on dose rate over the range of 800 mrad/min (8 mGy/min) to 90 rads/min (0.9 Gy/min). The dose rate dependence clearly implies a repair mechanism that is overwhelmed at the high dose rate. Geneticists estimate that there are 320 chances per million of a "spontaneous" mutation in a dominant gene trait of a person. The radiation dose that would eventually lead to a doubling of the mutation rate is estimated to be in the range of 50-250 rads (0.5-2.5 Gy).
Nonstochastic (Acute) Effects
Unlike stochastic effects, nonstochastic effects are characterized by a threshold dose below which they do not occur. In other words, nonstochastic effects have a clear relationship between the exposure and the effect. In addition, the magnitude of the effect is directly proportional to the size of the dose. Nonstochastic effects typically result when very large dosages of radiation are received in a short amount of time. These effects will often be evident within hours or days. Examples of nonstochastic effects include erythema (skin reddening), skin and tissue burns, cataract formation, sterility, radiation sickness and death. Each of these effects differs from the others in that both its threshold dose and the time over which the dose was received cause the effect (i.e. acute vs. chronic exposure).
There are a number of cases of radiation burns occurring to the hands or fingers. These cases occurred when a radiographer touched or came in close contact with a high intensity radiation emitter. Intensity on the surface of an 85 curie Ir-192 source capsule is approximately 1,768 R/s. Contact with the source for two seconds would expose the hand of an individual to 3,536 rems, and this does not consider any additional whole body dosage received when approaching the source.
More on Specific Nonstochastic Effects
The hemopoietic syndrome encompasses the medical conditions that affect the blood. Hemopoietic syndrome conditions appear after a gamma dose of about 200 rads (2 Gy). This disease is characterized by depression or ablation of the bone marrow, and the physiological consequences of this damage. The onset of the disease is rather sudden, and is heralded by nausea and vomiting within several hours after the overexposure occurred. Malaise and fatigue are felt by the victim, but the degree of malaise does not seem to be correlated with the size of the dose. Loss of hair (epilation), which is almost always seen, appears between the second and third week after the exposure. Death may occur within one to two months after exposure. The chief effects to be noted, of course, are in the bone marrow and in the blood. Marrow depression is seen at 200 rads and at about 400 to 600 rads (4 to 6 Gy) complete ablation of the marrow occurs. In this case, however, spontaneous regrowth of the marrow is possible if the victim survives the physiological effects of the denuding of the marrow. An exposure of about 700 rads (7 Gy) or greater leads to irreversible ablation of the bone marrow.
The gastrointestinal syndrome encompasses the medical conditions that affect the stomach and the intestines. This medical condition follows a total body gamma dose of about 1000 rads (10 Gy) or greater, and is a consequence of the desquamation of the intestinal epithelium. All the signs and symptoms of hemopoietic syndrome are seen, with the addition of severe nausea, vomiting, and diarrhea which begin very soon after exposure. Death within one to two weeks after exposure is the most likely outcome.
Central Nervous System
A total body gamma dose in excess of about 2000 rads (20 Gy) damages the central nervous system, as well as all the other organ systems in the body. Unconsciousness follows within minutes after exposure and death can result in a matter of hours to several days. The rapidity of the onset of unconsciousness is directly related to the dose received. In one instance in which a 200 msec burst of mixed neutrons and gamma rays delivered a mean total body dose of about 4400 rads (44 Gy), the victim was ataxic and disoriented within 30 seconds. In 10 minutes, he was unconscious and in shock. Vigorous symptomatic treatment kept the patient alive for 34 hours after the accident.
Other Acute Effects
Several other immediate effects of acute overexposure should be noted. Because of its physical location, the skin is subject to more radiation exposure, especially in the case of low energy x-rays and beta rays, than most other tissues. An exposure of about 300 R (77 mC/kg) of low energy (in the diagnostic range) x-rays results in erythema. Higher doses may cause changes in pigmentation, loss of hair, blistering, cell death, and ulceration. Radiation dermatitis of the hands and face was a relatively common occupational disease among radiologists who practiced during the early years of the twentieth century.
The reproductive organs are particularly radiosensitive. A single dose of only 30 rads (300 mGy) to the testes results in temporary sterility among men. For women, a 300 rad (3 Gy) dose to the ovaries produces temporary sterility. Higher doses increase the period of temporary sterility. In women, temporary sterility is evidenced by a cessation of menstruation for a period of one month or more, depending on the dose. Irregularities in the menstrual cycle, which suggest functional changes in the reproductive organs, may result from local irradiation of the ovaries with doses smaller than that required for temporary sterilization.
The eyes too, are relatively radiosensitive. A local dose of several hundred rads can result in acute conjunctivitis.
As discussed in the introduction, concern over the biological effect of ionizing radiation began shortly after the discovery of X-rays in 1895. Over the years, numerous recommendations regarding occupational exposure limits have been developed by the International Commission on Radiological Protection (ICRP) and other radiation protection groups. In general, the guidelines established for radiation exposure have had two principle objectives: 1) to prevent acute exposure; and 2) to limit chronic exposure to "acceptable" levels.
Current guidelines are based on the conservative assumption that there is no safe level of exposure. In other words, even the smallest exposure has some probability of causing a stochastic effect, such as cancer. This assumption has led to the general philosophy of not only keeping exposures below recommended levels or regulation limits but also maintaining all exposure "as low as reasonable achievable" (ALARA). ALARA is a basic requirement of current radiation safety practices. It means that every reasonable effort must be made to keep the dose to workers and the public as far below the required limits as possible.
Regulatory Limits for Occupational Exposure
Many of the recommendations from the ICRP and other groups have been
incorporated into the regulatory requirements of countries around the world. In
1) the more limiting of:
- A total effective dose equivalent of 5 rems (0.05 Sv) or The sum of the deep-dose equivalent to any individual organ or tissue other than the lens of the eye being equal to 50 rems (0.5 Sv).
2) The annual limits to the lens of the eye, to the skin, and to the extremities, which are:
- A lens dose equivalent of 15 rems (0.15 Sv)
- A shallow-dose equivalent of 50 rems (0.50 Sv) to the skin or to any extremity.
The shallow-dose equivalent is the external dose to the skin of
the whole-body or extremities from an external source of ionizing radiation.
This value is the dose equivalent at a tissue depth of
The lens dose equivalent is the dose equivalent to the lens of the eye from an external source of ionizing radiation. This value is the dose equivalent at a tissue depth of
The deep-dose equivalent is the whole-body dose from an external
source of ionizing radiation. This value is the dose equivalent at a tissue
The total effective dose equivalent is the dose equivalent to the whole-body.
Declared Pregnant Workers and Minors
Because of the increased health risks to the rapidly developing embryo and fetus, pregnant women can receive no more than 0.5 rem during the entire gestation period. This is 10% of the dose limit that normally applies to radiation workers. Persons under the age of 18 years are also limited to 0.5rem/year.
Non-radiation Workers and the Public
The dose limit to non-radiation workers and members of the public are two percent of the annual occupational dose limit. Therefore, a non-radiation worker can receive a whole body dose of no more that 0.1 rem/year from industrial ionizing radiation. This exposure would be in addition to the 0.3 rem/year from natural background radiation and the 0.05 rem/year from man-made sources such as medical x-rays.
Controlling Radiation Exposure
When working with radiation, there is a concern for two types of exposure: acute and chronic. An acute exposure is a single accidental exposure to a high dose of radiation during a short period of time. An acute exposure has the potential for producing both nonstochastic and stochastic effects. Chronic exposure, which is also sometimes called "continuous exposure," is long-term, low level overexposure. Chronic exposure may result in stochastic health effects and is likely to be the result of improper or inadequate protective measures.
The three basic ways of controlling exposure to harmful radiation are: 1) limiting the time spent near a source of radiation, 2) increasing the distance away from the source, 3) and using shielding to stop or reduce the level of radiation.
The radiation dose is directly proportional to the time spent in the radiation. Therefore, a person should not stay near a source of radiation any longer than necessary. If a survey meter reads 4 mR/h at a particular location, a total dose of 4mr will be received if a person remains at that location for one hour. In a two hour span of time, a dose of 8 mR would be received. The following equation can be used to make a simple calculation to determine the dose that will be or has been received in a radiation area.
Dose = Dose Rate x Time
When using a gamma camera, it is important to get the source from the shielded camera to the collimator as quickly as possible to limit the time of exposure to the unshielded source. Devices that shield radiation in some directions but allow it pass in one or more other directions are known as collimators. This is illustrated in the images at the bottom of this page.
Increasing distance from the source of radiation will reduce the amount of radiation received. As radiation travels from the source, it spreads out becoming less intense. This is analogous to standing near a fire. The closer a person stands to the fire, the more intense the heat feels from the fire. This phenomenon can be expressed by an equation known as the inverse square law, which states that as the radiation travels out from the source, the dosage decreases inversely with the square of the distance.
Inverse Square Law: I1/ I2 = D22/ D12
The third way to reduce exposure to radiation is to place something between the radiographer and the source of radiation. In general, the denser the material the more shielding it will provide. The most effective shielding is provided by depleted uranium metal. It is used primarily in gamma ray cameras like the one shown below. The circle of dark material in the plastic see-through camera (below right) would actually be a sphere of depleted uranium in a real gamma ray camera. Depleted uranium and other heavy metals, like tungsten, are very effective in shielding radiation because their tightly packed atoms make it hard for radiation to move through the material without interacting with the atoms. Lead and concrete are the most commonly used radiation shielding materials primarily because they are easy to work with and are readily available materials. Concrete is commonly used in the construction of radiation vaults. Some vaults will also be lined with lead sheeting to help reduce the radiation to acceptable levels on the outside.
Half-Value Layer (Shielding)
As was discussed in the radiation theory section, the depth of penetration for a given photon energy is dependent upon the material density (atomic structure). The more subatomic particles in a material (higher Z number), the greater the likelihood that interactions will occur and the radiation will lose its energy. Therefore, the denser a material is the smaller the depth of radiation penetration will be. Materials such as depleted uranium, tungsten and lead have high Z numbers, and are therefore very effective in shielding radiation. Concrete is not as effective in shielding radiation but it is a very common building material and so it is commonly used in the construction of radiation vaults.
Since different materials attenuate radiation to different degrees, a convenient method of comparing the shielding performance of materials was needed. The half-value layer (HVL) is commonly used for this purpose and to determine what thickness of a given material is necessary to reduce the exposure rate from a source to some level. At some point in the material, there is a level at which the radiation intensity becomes one half that at the surface of the material. This depth is known as the half-value layer for that material. Another way of looking at this is that the HVL is the amount of material necessary to the reduce the exposure rate from a source to one-half its unshielded value.
Sometimes shielding is specified as some number of HVL. For example, if a Gamma source is producing 369 R/h at one foot and a four HVL shield is placed around it, the intensity would be reduced to 23.0 R/h.
Each material has its own specific HVL thickness. Not only is the HVL material dependent, but it is also radiation energy dependent. This means that for a given material, if the radiation energy changes, the point at which the intensity decreases to half its original value will also change. Below are some HVL values for various materials commonly used in industrial radiography. As can be seen from reviewing the values, as the energy of the radiation increases the HVL value also increases.
Approximate HVL for Various Materials when Radiation is from a Gamma Source
Half-Value Layer, mm (inch)
Approximate Half-Value Layer for Various Materials when Radiation is from an X-ray Source
Half-Value Layer, mm (inch)
Peak Voltage (kVp)
Note: The values presented on this page are intended for educational purposes. Other sources of information should be consulted when designing shielding for radiation sources
Since X-ray and gamma radiation are not detectable by the human senses and the resulting damage to the body is not immediately apparent, a variety of safety controls are used to limit exposure. The two basic types of radiation safety controls used to provide a safe working environment are engineered and administrative controls. Engineered controls include shielding, interlocks, alarms, warning signals, and material containment. Administrative controls include postings, procedures, dosimetry, and training.
Engineered controls such as shielding and door interlocks are used to contain the radiation in a cabinet or a "radiation vault." Fixed shielding materials are commonly high density concrete and/or lead. Door interlocks are used to immediately cut the power to X-ray generating equipment if a door is accidentally opened when X-rays are being produced. Warning lights are used to alert workers and the public that radiation is being used. Sensors and warning alarms are often used to signal that a predetermined amount of radiation is present. Safety controls should never be tampered with or bypassed.
When portable radiography is performed, it is most often not practical to place alarms or warning lights in the exposure area. Ropes and signs are used to block the entrance to radiation areas and to alert the public to the presence of radiation. Occasionally, radiographers will use battery operated flashing lights to alert the public to the presence of radiation. Portable or temporary shielding devices may be fabricated from materials or equipment located in the area of the inspection. Sheets of steel, steel beams, or other equipment may be used for temporary shielding. It is the responsibility of the radiographer to know and understand the absorption value of various materials. More information on absorption values and material properties can be found in the radiography section of this site.
As mentioned above, administrative controls supplement the engineered
controls. These controls include postings, procedures, dosimetry, and training.
It is commonly required that all areas containing X-ray producing equipment or
radioactive materials have signs posted bearing the radiation symbol and a
notice explaining the dangers of radiation. Normal operating procedures and
emergency procedures must also be prepared and followed. In the
Instruments used for radiation measurement fall into two broad
- rate measuring instruments and - personal dose measuring instruments.Rate measuring instruments measure the rate at which exposure is received (more commonly called the radiation intensity). Survey meters, audible alarms and area monitors fall into this category. These instruments present a radiation intensity reading relative to time, such as R/hr or mR/hr. An analogy can be made between these instruments and the speedometer of a car because both are measuring units relative to time.
Dose measuring instruments are those that measure the total amount of exposure received during a measuring period. The dose measuring instruments, or dosimeters, that are commonly used in industrial radiography are small devices which are designed to be worn by an individual to measure the exposure received by the individual. An analogy can be made between these instruments and the odometer of a car because both are measuring accumulated units.
The radiation measuring instruments commonly used in industrial radiography are described in more detail in the following pages.
The survey meter is the most important resource a radiographer has to determine the presence and intensity of radiation. A review of incident and overexposure reports indicate that a majority of these type of events occurred when a technician did not have or did not use a survey meter.
There are many different models of survey meters available to measure radiation in the field. They all basically consist of a detector and a readout display. Analog and digital displays are available. Most of the survey meters used for industrial radiography use a gas filled detector.
Gas filled detectors consists of consists of a gas filled cylinder with two electrodes. Sometimes, the cylinder itself acts as one electrode, and a needle or thin taut wire along the axis of the cylinder acts as the other electrode. A voltage is applied to the device so that the central needle or wire become an anode (+ charge) and the other electrode or cylinder wall becomes the cathode (- charge). The gas becomes ionized whenever the counter is brought near radioactive substances. The electric field created by the potential difference between the anode and cathode causes the electrons of each ion pair to move to the anode while the positively charged gas atom is drawn to the cathode. This results in an electrical signal that is amplified, correlated to exposure and displayed as a value.
Depending on the voltage applied between the anode and the cathode, the detector may be considered an ion chamber, a proportional counter, or a Geiger-Müller (GM) detector. Each of these types of detectors have their advantages and disadvantages. A brief summary of each of these detectors follows.
Ion Chamber Counter
Ion chambers have a relatively low voltage between the anode and cathode, which results in a collection of only the charges produced in the initial ionization event. This type of detector produces a weak output signal that corresponds to the number of ionization events. Higher energies and intensities of radiation will produce more ionization, which will result in a stronger output voltage.
Collection of only primary ions provides information on true radiation exposure (energy and intensity). However, the meters require sensitive electronics to amplify the signal, which makes them fairly expensive and delicate. The additional expense and required care is justified when it is necessary to make accurate radiation exposure measurements over a range of radiation energies. This might be necessary when measuring the Bremsstrahlung radiation produced by an X-ray generator. An ion chamber survey meter is sometimes used in the field when performing gamma radiography because it will provide accurate exposure measurements regardless of the radioactive isotope being used.
Proportional counter detectors use a slightly higher voltage between the anode and cathode. Due to the strong electrical field, the charges produced in the initial ionization are accelerated fast enough to ionize other electrons in the gas. The electrons produced in these secondary ion pairs, along with the primary electrons, continue to gain energy as they move towards the anode, and as they do, they produce more and more ionizations. The result is that each electron from a primary ion pair produces a cascade of ion pairs. This effect is known as gas multiplication or amplification. In this voltage regime, the number of particles liberated by secondary interactions is proportional to the number of ions produced by the passing ionizing particle. Hence, these gas ionization detectors are called proportional counters.
Like ion chamber detectors, proportional detectors discriminate between types of radiation. However, they require very stable electronics which are expensive and fragile. Proportional detectors are usually only used in a laboratory setting.
Geiger-Müller (GM) Counter
Geiger-Müller counters operate under even higher voltages between the anode and the cathode, usually in the 800 to 1200 volt range. Like the proportional counter, the high voltage accelerates the charges produced in the initial ionization to where they have enough energy to ionize other electrons in the gas. However, this cascading of ion pairs occurs to a much larger degree and continues until the counter is saturated with ions. This all happens in a fraction of a second and results in an electrical current pulse of constant voltage. The collection of the large number of secondary ions in the GM region is known as an avalanche and produces a large voltage pulse. In other words, the size of the current pulse is independent of the size of the ionization event that produced it.
The electronic circuit of a GM counters counts and records the number of pulses and the information is often displayed in counts per minute. If the instrument has a speaker, the pulses can also produce an audible click. When the volume of gas in the chamber is completely ionized, ion collection stops until the electrical pulse discharges. Again, this only takes a fraction of a second, but this process slightly limits the rate at which individual events can be detected.
Because they can display individual ionizing events, GM counters are generally more sensitive to low levels of radiation than ion chamber instruments. By means of calibration, the count rate can be displayed as the exposure rate over a specified energy range. When used for gamma radiography, GM meters are typically calibrated for the energy of the gamma radiation being used. Most often, gamma radiation from Cs-137 at 0.662 MeV provides the calibration. Only small errors occur when the radiographer uses Ir-192 (average energy about 0.34 MeV) or Co-60 (average energy about 1.25 MeV).
Since the Geiger-Müller counter produces many more electrons than a ion chamber counter or a proportional counter, it does not require the same level of electronic sophistication as other survey meters. This results in a meter that is relatively low cost and rugged. The disadvantages of GM survey meters are the lack of ability to account for different amounts of ionization caused by different energy photons and noncontinuous measurement (need to discharge).
Comparison of Gas Filled Detectors
The graph to the right shows the relationship of ion collection in a gas filled detector versus the applied voltage. In the ion chamber region, the voltage between the anode and cathode is relatively low and only primary ions are collected. In the proportional region ,the voltage is higher, and primary ions and a number of secondary ions (proportional to the primary ions originally formed) are collected. In the GM region, a maximum number of secondary ions are collected when the gas around the anode is completely ionized. Note that discrimination between kinds of radiation (E1 and E2) is possible in the ion chamber and proportional regions. Radiation at different energy levels forms different numbers of primary ions in the detector. However in the GM region, the number of secondary ions collected per event remains the same no matter what the energy of the radiation that initiated the event. The GM counter gives up the ability to accurately measure the exposure due to different energies of radiation in exchange for a large signal pulse. This large signal pulse simplifies the electronics that are necessary for instruments such as survey meters.
Pocket dosimeters are used to provide the wearer with an immediate reading of his or her exposure to x-rays and gamma rays. As the name implies, they are commonly worn in the pocket. The two types commonly used in industrial radiography are the Direct Read Pocket Dosimeter and the Digital Electronic Dosimeter.
Direct Read Pocket Dosimeter
A direct reading pocket ionization dosimeter is generally of the size and shape of a fountain pen. The dosimeter contains a small ionization chamber with a volume of approximately two milliliters. Inside the ionization chamber is a central wire anode, and attached to this wire anode is a metal coated quartz fiber. When the anode is charged to a positive potential, the charge is distributed between the wire anode and quartz fiber. Electrostatic repulsion deflects the quartz fiber, and the greater the charge, the greater the deflection of the quartz fiber. Radiation incident on the chamber produces ionization inside the active volume of the chamber. The electrons produced by ionization are attracted to, and collected by, the positively charged central anode. This collection of electrons reduces the net positive charge and allows the quartz fiber to return in the direction of the original position. The amount of movement is directly proportional to the amount of ionization which occurs.
By pointing the instrument at a light source, the position of the fiber may be observed through a system of built-in lenses. The fiber is viewed on a translucent scale which is graduated in units of exposure. Typical industrial radiography pocket dosimeters have a full scale reading of 200 milliroentgens but there are designs that will record higher amounts. During the shift, the dosimeter reading should be checked frequently. The measured exposure should be recorded at the end of each shift.
The principal advantage of a pocket dosimeter is its ability to provide the wearer an immediate reading of his or her radiation exposure. It also has the advantage of being reusable. The limited range, inability to provide a permanent record, and the potential for discharging and reading loss due to dropping or bumping are a few of the main disadvantages of a pocket dosimeter. The dosimeters must be recharged and recorded at the start of each working shift. Charge leakage, or drift, can also affect the reading of a dosimeter. Leakage should be no greater than 2 percent of full scale in a 24 hour period.
Digital Electronic Dosimeter
Another type of pocket dosimeter is the Digital Electronic Dosimeter. These dosimeters record dose information and dose rate. These dosimeters most often use Geiger-Müller counters. The output of the radiation detector is collected and, when a predetermined exposure has been reached, the collected charge is discharged to trigger an electronic counter. The counter then displays the accumulated exposure and dose rate in digital form.
Some Digital Electronic Dosimeters include an audible alarm feature which emits an audible signal or chirp with each recorded increment of exposure. Some models can also be set to provide a continuous audible signal when a preset exposure has been reached. This format helps to minimize the reading errors associated with direct reading pocket ionization chamber dosimeters and allows the instrument to achieve a higher maximum readout before resetting is necessary.
Audible Alarm Rate Meters and Digital Electronic Dosimeters
Audible alarms are devices that emit a short "beep" or "chirp" when a predetermined exposure has been received. It is required that these electronic devices be worn by an individual working with gamma emitters. These devices reduce the likelihood of accidental exposures in industrial radiography by alerting the radiographer to dosages of radiation above a preset amount. Typical alarm rate meters will begin sounding in areas of 450-500 mR/h. It is important to note that audible alarms are not intended to be and should not be used as replacements for survey meters.
Most audible alarms use a Geiger-Müller detector. The output of the detector is collected, and when a predetermined exposure has been reached, this collected charge is discharged through a speaker. Hence, an audible "chirp" is emitted. Consequently, the frequency or chirp rate of the alarm is proportional to the radiation intensity. The chirp rate varies among different alarms from one chirp per milliroentgen to more than 100 chirps per milliroentgen
Personnel dosimetry film badges are commonly used to measure and record radiation exposure due to gamma rays, X-rays and beta particles. The detector is, as the name implies, a piece of radiation sensitive film. The film is packaged in a light proof, vapor proof envelope preventing light, moisture or chemical vapors from affecting the film.
A special film is used which is coated with two different emulsions. One side is coated with a large grain, fast emulsion that is sensitive to low levels of exposure. The other side of the film is coated with a fine grain, slow emulsion that is less sensitive to exposure. If the radiation exposure causes the fast emulsion in the processed film to be darkened to a degree that it cannot be interpreted, the fast emulsion is removed and the dose is computed using the slow emulsion.
The film is contained inside a film holder or badge. The badge incorporates a series of filters to determine the quality of the radiation. Radiation of a given energy is attenuated to a different extent by various types of absorbers. Therefore, the same quantity of radiation incident on the badge will produce a different degree of darkening under each filter. By comparing these results, the energy of the radiation can be determined and the dose can be calculated knowing the film response for that energy. The badge holder also contains an open window to determine radiation exposure due to beta particles. Beta particles are effectively shielded by a thin amount of material.
The major advantages of a film badge as a personnel monitoring device are that it provides a permanent record, it is able to distinguish between different energies of photons, and it can measure doses due to different types of radiation. It is quite accurate for exposures greater than 100 millirem. The major disadvantages are that it must be developed and read by a processor (which is time consuming), prolonged heat exposure can affect the film, and exposures of less than 20 millirem of gamma radiation cannot be accurately measured.
Film badges need to be worn correctly so that the dose they receive accurately represents the dose the wearer receives. Whole body badges are worn on the body between the neck and the waist, often on the belt or a shirt pocket. The clip-on badge is worn most often when performing X-ray or gamma radiography. The film badge may also be worn when working around a low curie source. Ring badges are worn on a finger of the hand most likely to be exposed to ionizing radiation. A LIXI system with its culminated and directional beam would be one example where monitoring the hands would be more important than the whole body.
Thermoluminescent dosimeters (TLD) are often used instead of the film badge. Like a film badge, it is worn for a period of time (usually 3 months or less) and then must be processed to determine the dose received, if any. Thermoluminescent dosimeters can measure doses as low as 1 millirem, but under routine conditions their low-dose capability is approximately the same as for film badges. TLDs have a precision of approximately 15% for low doses. This precision improves to approximately 3% for high doses. The advantages of a TLD over other personnel monitors is its linearity of response to dose, its relative energy independence, and its sensitivity to low doses. It is also reusable, which is an advantage over film badges. However, no permanent record or re-readability is provided and an immediate, on the job readout is not possible.
How it works
A TLD is a phosphor, such as lithium fluoride (LiF) or calcium fluoride (CaF), in a solid crystal structure. When a TLD is exposed to ionizing radiation at ambient temperatures, the radiation interacts with the phosphor crystal and deposits all or part of the incident energy in that material. Some of the atoms in the material that absorb that energy become ionized, producing free electrons and areas lacking one or more electrons, called holes. Imperfections in the crystal lattice structure act as sites where free electrons can become trapped and locked into place.
Heating the crystal causes the crystal lattice to vibrate, releasing the trapped electrons in the process. Released electrons return to the original ground state, releasing the captured energy from ionization as light, hence the name thermoluminescent. Released light is counted using photomultiplier tubes and the number of photons counted is proportional to the quantity of radiation striking the phosphor.
Instead of reading the optical density (blackness) of a film, as is done with film badges, the amount of light released versus the heating of the individual pieces of thermoluminescent material is measured. The "glow curve" produced by this process is then related to the radiation exposure. The process can be repeated many times.