Cat. No.: H46-2/91-151E
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This document is one of a series of safety codes prepared by the Bureau of Radiation and Medical Devices to set out requirements for the safe use of radiation-emitting equipment. Included in this code are sections for the specific guidance of the veterinarian, the operator and the health physicist concerned with safety procedures, equipment performance and protection surveys.
The safety procedures, equipment and installation guidelines detailed in this code are primarily for the instruction and guidance of persons employed in Federal Public Service departments and agencies, as well as those under the jurisdiction of the Canada Labour Code. Facilities under provincial jurisdiction may be subject to requirements specified under provincial statutes. The authorities listed in Appendix IV should be contacted for details of the regulatory requirements of individual provinces.
The words "must" and "should" in this code have been chosen with purpose. The word "must" indicates a recommendation that is essential to meet the currently accepted standards of protection, while "should" indicates an advisory recommendation that is highly desirable and should be implemented where applicable.
In a field in which technology is advancing rapidly and where unexpected and unique problems continually occur, the code cannot cover all possible situations. Blind adherence to rules cannot substitute for the exercise of sound judgement. Recommendations may be modified in unusual circumstances but only upon the advice of experts with recognized competence in radiation protection. This code will be reviewed and revised periodically, and a particular requirement may be reconsidered at any time if it becomes necessary to cover an unforeseen situation. Interpretation or elaboration on any point can be obtained by contacting the Bureau of Radiation and Medical Devices, Department of National Health and Welfare, Ottawa, Ontario K1A 1C1.
This code reflects the results of the work of many individuals. It was prepared and compiled by Mr. C. Lavoie and reviewed by the professional staff of the X-Ray Section, Bureau of Radiation and Medical Devices.
Appreciation is expressed to all organizations, agencies and individuals whose comments and suggestions helped in the preparation of this code.
Diagnostic radiology is an essential part of present-day veterinary practice. The need for radiation protection exists because occupational exposure to ionizing radiation can result in deleterious effects that may manifest themselves not only in exposed individuals but in their descendants as well. These are respectively called somatic and genetic effects. Somatic effects are characterized by observable changes occurring in the body organs of the exposed individual. These changes may appear from within a few hours to many years later, depending on the amount and duration of exposure of the individual. In veterinary medicine, the possibility that anyone may be exposed to enough radiation to create somatic effect is extremely remote. Genetic effects are more a cause for concern at the lower doses used in veterinary radiology. Although the radiation doses may be small and appear to cause no observable damage, the probability of chromosomal damage in the germ cells, with the consequence of mutations, does exist. These mutations may give rise to genetic defects and therefore make these doses significant when applied to a large number of individuals.
There are two main aspects of the problem to be considered. First, personnel working with X-ray equipment must be protected from excessive exposure to radiation during their work. Secondly, personnel in the vicinity of veterinary X-ray facilities and the general public require adequate protection.
This safety code is concerned with the protection of all individuals who may be exposed to radiation emitted by X-ray equipment used in the practice of veterinary radiology.
The principal aims of this code are:
To assist personnel in achieving these objectives, this safety code:
The owner is ultimately responsible for the radiation safety of a veterinary X-ray facility. It is the responsibility of the owner to ensure that the X-ray equipment provided for the responsible user and operators, and the facility in which such equipment is installed and used meet all applicable radiation safety standards.
The owner may delegate this responsibility to staff. How this responsibility is delegated will depend upon the number of staff members and on the amount of X-ray equipment owned. In any event, one or more persons must be designated to carry out the roles described below.
There must be at least one person designated as the responsible user (veterinarian, animal health technologist, registered radiology technician) to undertake responsibility for:
All operators must:
A female operator should be encouraged to notify her employer if she believes herself pregnant. Appropriate steps may then be taken to ensure that her work duties during the remainder of the pregnancy are compatible with the permissible dose equivalent limits, as set out in Appendix I.
All students, operators-in-training and personnel not experienced in the use of X-ray equipment must work only under the direct supervision of a qualified operator. Dose equivalent limits for students and operators-in-training should not be greater than the limits set for members of the public.
In the planning of any veterinary X-ray facility, account must be taken of the expected maximum workload of the equipment, use factors of the barriers and occupancy factors for areas adjacent to the facility. Allowance should be made for possible future changes in any of these parameters, such as increased operating X-ray tube voltage and workload or an increase in the degree of occupancy of surrounding areas.
It is particularly advantageous to make visual inspections during construction of a new facility to ensure compliance with specifications and to identify faulty material or workmanship. Deficiencies can be remedied more economically at this stage than later. Such inspections should verify the thickness and density of all barriers, including lead sheets, concrete walls and shielding glass used in viewing windows.
Certain basic principles must be observed when determining the shielding requirements for a room used routinely for veterinary radiological procedures.
In general, radiation levels close to the X-ray equipment are such that the above limits are exceeded even at very low workloads. Reductions in radiation intensity can be accomplished by interposing physical barriers or increasing the distance between the sources of radiation and the persons to be protected.
The shielding required to reduce radiation levels to acceptable values may be determined on the basis of distance, nominal X-ray tube voltage, and workload. To ensure that the radiation levels are always below acceptable limits, the maximum expected workload should be used.
The procedures described below must be followed to protect personnel working with or in the vicinity of X-ray equipment.
A radiation protection survey of a facility is intended to demonstrate not only that the X-ray equipment itself functions properly and according to applicable standards, but also that the equipment is installed and used in a way that maximum radiation safety for operators and others. Therefore it is important that X-ray facilities be inspected at regular intervals.
Before routine operation of any new facility, the owner of the facility must contact the appropriate agency to enquire about the inspection procedures in that jurisdiction. Some jurisdictions may require the facility to be declared in compliance with applicable government regulations prior to operation. In an existing facility, a survey must be carried out after any change that may increase radiation output of the equipment or affect protection of the operator or others, e.g. alterations of protective barriers, replacement of the X-ray machine with one capable of operating at a higher X-ray tube voltage, changes in operating procedures or increased workload.
The results of such surveys and conclusions drawn by a qualified expert must be submitted to the owner or responsible user in a written report. All such written reports must be retained by the owner or responsible user.
The survey report must present any unusual findings about the equipment itself, the installation or operating procedures that could affect the safety of operators or other persons in the vicinity of the X-ray facility. The survey report should also include the results of investigations of any unusually high exposures from previous personal dosimetry reports and recommend whether other persons should use personal dosimeters.
The survey report must include at least the following:
All veterinary X-ray equipment and accessories for such equipment sold in Canada must conform to the Radiation Emitting Devices Act and the Food and Drugs Act. There are no specific standards promulgated for veterinary X-ray equipment under the Radiation Emitting Devices Act, but this equipment must comply with the general provisions of the Act. The requirements of the Food and Drugs Act are specified in the Medical Devices Regulations promulgated under this Act. It is the responsibility of the manufacturer or distributor to ensure that the equipment conforms to the requirements stated in these Acts.
Modifications to these requirements may be made from time to time to keep abreast of changing technology in the field of radiation protection and veterinary medicine. Information on the applicability and currency of the Radiation Emitting Devices Act and the Medical Devices Regulations may the obtained by contacting the Bureau of Radiation and Medical Devices, Department of National Health and Welfare, Ottawa, Ontario K1A 1C1.
Whenever possible and to the extent that is practical, existing X-ray equipment should be upgraded to incorporate as many as possible of the safety and performance features described below. New X-ray equipment should also incorporate as many as possible of the safety and performance features described.
To ensure maximum protection for staff and visitors, all X-ray equipment should at least meet certain basic requirements.
Protective aprons, gloves and thyroid shields used for veterinary X-ray examinations must provide attenuation equivalent to at least 0.5 mm of lead at X-ray tube voltages of up to 150 kVp. The lead equivalent thickness of the material used must be permanently and legibly marked on the protective device. Protection must be provided throughout the glove, including fingers and wrist.
Protective aprons, gloves and thyroid shields must be stored and maintained according to manufacturers' recommendations. It is also recommended that protective aprons, gloves and thyroid shields are checked by radiographing them annually or when damage is suspected.
The irradiation necessary to produce a radiogram of satisfactory diagnostic quality depends not only on the loading technique and the film-screen combination employed but also on the handling and processing of the film. Improper processing of radiographic film can cause films of poor diagnostic quality that may require an increase in loading factors or repeat irradiations. This would lead to an increase in the exposure level of scatter and leakage radiations to the staff. Adherence to the following guidelines on darkroom design, film processing and film storage will improve the diagnostic quality of films and ultimately reduce radiation levels in the facility.
The guidelines and procedures outlined in this section are primarily directed toward occupational health protection. Adherence to these guidelines will also provide protection to visitors and other individuals in the vicinity of an X-ray facility. However, the safe work practices and procedures for using various types of X-ray equipment should be regarded as a minimum to be augmented with additional requirements, when warranted, to cover special circumstances in particular facilities.
To achieve optimum safety, operators must make every reasonable effort to keep exposures to themselves and to other personnel as low as reasonably achievable, with the limits specified in Appendix I being regarded as maximum values not to be exceeded.
For the purpose of radiation protection, individuals may be classified in one of two categories: those exposed to radiation during the course of their work (radiation workers), and others. Maximum permissible levels are given for both categories in the following table. These dose equivalent limits are based on the latest recommendations of the International Commission on Radiological Protection (ICRP) as specified in ICRP Publication 60.
Permissible dose equivalent limits for radiation workers apply only to irradiation resulting directly from their occupations and do not include irradiation from other sources such as medical diagnoses and background radiation.
|Annual permissible dose equivalent limits|
organ or tissue
|Other workers and
members of the public
|Whole body||20 mSv||1 mSv|
|Lens of the eye||150 mSv||15 mSv|
|Skin||500 mSv||50 mSv|
|Hands||500 mSv||50 mSv|
|All other organs||500 mSv||50 mSv|
To determine the shielding necessary for a veterinary X-ray facility, certain preliminary information is essential. In many instances the thickness of lead or concrete required to reduce radiation levels to the maximum permissible level can be determined directly from Tables 1 and 2 of this Appendix. In other cases, contact the appropriate agency to enquire about shielding requirements and calculations. In both instances answers to the following questions are required.
The tabulated values give the minimum amount of lead or concrete shielding required to reduce the exposure in uncontrolled areas to 17.5 µGy (2 mR) in one week. These thicknesses of shielding are for a single source of radiation. If more than one source irradiates the location of interest, the contribution from each source must be taken into account in determining the amount of shielding required. Planned and existing structural materials should be fully considered when calculating a barrier requirement.
The thicknesses of lead and concrete required have been rounded off to the next highest 0.05 mm and 0.5 cm respectively.
Note: lead sheet is commercially available only in discrete thicknesses given in Table 3.
mm of lead required at
a source distance of
cm of concrete required at
a source distance of
mm of lead required at
a source distance of
mm of conrete required at
a source distance of
Commonly used construction materials provide a certain degree of protection against X-radiation. This degree will depend on the type and thickness of the material in question and on the X-ray tube voltage at which the equipment is operated. In some cases a judicious use of common building materials or a careful selection of location and orientation of the X-ray unit may eliminate the need for additional shielding without compromising the X-ray safety of the installation.
X-ray shielding properties of some common construction materials and their combinations are given below. Note that thicknesses of different materials that provide equivalent attenuation under one set of conditions may behave quite differently under other conditions. The materials described in Table 4 are not well suited for use as primary shielding. They should be regarded as materials for use in secondary shielding.
|Material||Thickness of concrete (cm)|
|50 kVp||70 kVp||85 kVp||100 kVp||125 kVp||150 kVp|
|Table 4 footnote 1||10||10||10||10||10||10|
|Table 4 footnote 2||7||7||7||7||7||7|
|Table 4 footnote 3||2.3||2.3||2.3||2.3||Table 4 footnote *||Table 4 footnote *|
|Table 4 footnote 4||0.5||0.5||0.5||0.5||Table 4 footnote *||Table 4 footnote *|
|Table 4 footnote 5||0.8||0.8||0.8||0.8||Table 4 footnote *||Table 4 footnote *|
|Table 4 footnote 6||1.0||1.0||1.0||1.0||Table 4 footnote *||Table 4 footnote *|
|Table 4 footnote 7||1.4||1.4||1.4||1.4||Table 4 footnote *||Table 4 footnote *|
|Table 4 footnote 8||1.2||1.2||1.2||1.2||1.2||1.2|
|Table 4 footnote 9||2.4||2.2||2.2||2.2||2.2||2.2|
Table 4 footnotes
To reduce the radiation level to the film to 1.75 µGy (0.2 mR) for weekly workloads of:
Distance from X-ray tube to stored film
|lead mm||concrete cm||lead mm||concrete cm||lead mm||concrete cm||lead mm||concrete cm|
|Storage time for primary barriers|
|For secondary barriers|
|lead mm||concrete cm||lead mm||concrete cm||lead mm||concrete cm||lead mm||concrete cm|
Radiation Health Section
Occupational Health Branch
Division of Policy and Professional Services
Government of Alberta
10709 Jasper Avenue
Edmonton, Alberta T5J 3N3
Worker's Compensation Board of British Columbia
P.O. Box 5350 Stn Terminal
Vancouver, British Columbia
Radiation Protection Section
Manitoba Cancer Treatment and Research Foundation
100 Olivia Street
Radiation Protection Services
Department of Health and Community Services
Government of New Brunswick
P.O. Box 5100
348 King Street
Fredericton, New Brunswick
Medical and Hygiene Services
Employment and Labour Relations
Government of Newfoundland
P.O. Box 8700
St. John's, Newfoundland
Occupational Health and Safety Division
Safety and Public Services
Government of the Northwest Territories
Yellowknife, Northwest Territories
Department of Health and Fitness
Government of Nova Scotia
7th Floor, Joseph Howe Building
P.O. Box 488
Halifax, Nova Scotia
Radiation Protection Service
Ontario Ministry of Labour
81 Resources Road
Division of Community Hygiene
Department of Health and Social Services
Government of Prince Edward Island
P.O. Box 2000
Charlottetown, Prince Edward Island
Division de la radioprotection
Ministère de l'environnement Gouvernement du Québec
5199 est, rue Sherbrooke
Radiation Safety Unit
Department of Human Resources, Labour and Employment
Government of Saskatchewan
1870 Albert Place
Occupational Health and Safety
Government of the Yukon Territory
P.O. Box 2703
Whitehorse, Yukon Territory
The unit of COULOMB/KILOGRAM (C/kg) has not found acceptance as the replacement of the ROENTGEN (R) as a unit of irradiation.
Following the lead of the International Electrotechnical Commission, the AIR KERMA (in GRAYS) replaces the EXPOSURE (in ROENTGENS) as the measure of irradiation. The relationship between the two units is as follows:
The GRAY (Gy) replaces the RAD (rad) as the unit of absorbed dose. The relationship between the two units is as follows:
The SIEVERT (Sv) replaces the REM (rem) as the unit of DOSE EQUIVALENT. The relationship between the two units is as follows:
Note: m = milli = 10-3; µ = micro = 10-6
Further details on the topics covered in this safety code may be obtained from the references listed below.