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Protection of Workers and Patients in Radiology

All exposures should be kept As Low As Reasonably Achievable (ALARA), economic and social factors being taken into account, for the workers, patients and general public.

Medical and supporting staff whose work involves the use of diagnostic x-rays can reduce their occupational exposures through adequate shielding of the x-ray facility and proper functioning of x-ray equipment (See Diagnostic X-ray Facility Protection), and by following radiation safety procedures during day-to-day operations. X-ray employees should read and understand the safety requirements contained in the facility’s radiation safety manual.

Details on the best ways to achieve the optimization of worker exposure can be found in the following guides:

 
  • The exposure of patients to ionizing radiation for diagnostic purposes must be justified – Referral rules should be implemented for this purpose.
  • When justified, the exposure of patients must be optimized, i.e. diagnostic images should be obtained at the lowest patient dose possible.
 
  1. Justification of a practice: Any practice involving exposure to radiation must be justified by the benefit it provides
  2. Optimization of radiation protection: all exposures should be kept As Low As Reasonably Achievable (ALARA), economic and social factors being taken into account
  3. Dose limitation: Dose limits must be applied to provide an adequate standard of protection to radiation workers

Note: Dose limits apply only to occupational exposure; they do not apply to the exposure of patients.

 

Occupational exposures to medical x-rays in British Columbia are regulated provincially by WorkSafeBC (WSBC) and federally by Health Canada. Based on WSBCs Occupational Health and Safety Regulations, the dose limits for workers are:

  • an annual effective dose of 20 mSv (whole-body dose)
  • an annual equivalent dose of:
    • 150 mSv to the lens of the eye
    • 500 mSv to the skin, averaged over any 1 cm2 regardless of the area exposed, and
    • 500 mSv to the hands and feet

In addition to these dose limits, WSBC has also defined an Action Level of 1.0 mSv/y. If the exposure of the worker exceeds or may exceed an annual dose of 1.0 mSv, employers must:

  • provide and ensure the proper use by workers of an acceptable dosimeter or radiation badge;
  • perform radiation surveys to measure radiation levels in work areas; and
  • provide written instructions on safe and proper procedures and practices related to the use of the radiation-emitting device.

Other requirements are listed in WSBCs Occupational Health and Safety Regulations Part 7.

 

Special limits are imposed for pregnant workers as an additional control to enhance the protection of the unborn child. ICRP guidance for pregnant workers can be found in Pregnancy and Medical Radiation (ICRP 84) or as a PowerPoint presentation. The worker should inform the employer once she knows of her pregnancy. Once the worker has declared her pregnancy, the dosimeter reporting period can be changed to 2-week intervals. Special limits apply for the pregnant worker for the remainder of her pregnancy -- in WSBCs Occupational Health and Safety Regulations is the lesser of:

  • effective dose of 4 mSv
  • dose limit specified for pregnant workers under the Nuclear Safety and Control Act or any successor legislation, and the regulations under that Act.

RIN 5 - Foetal Dose from Maternal Diagnostic X-ray Examinations document provides guidance for practitioners in the radiology field when addressing embryo dose.

 

For more information, refer to RIN 7 - Update On Personal Dosimetry Services, which provides an advisory on personal radiation dosimetry services in Canada. 


RIN 13 - Procedures for Reporting and Investigating High Occupational Radiation Exposure Notifications. An employer may receive a notification from the dosimetry service provider or from the National Dose Registry (NDR) of Canada (NDR), indicating that an employee has exceeded an applicable dose limit. These notifications can result from a high dose on an individual badge or from the accumulation of the doses received from badges worn during the year. The employer is responsible for taking action on receipt of a notification.


RIN 21 - Guideline for Wearing Radiation Monitoring Devices [Personal Dosimeters] or TLDs: provides guidance to owners/operators in facilities where ionizing radiation is used on the need for wearing personal radiation monitoring devices (i.e. dosimetry badges).


RIN 22 - Guidelines for Workers Assisting During Medical X-ray Procedures provides guidance for workers who assist in medical procedures that involve the use of x-ray equipment.

 

The following three dosimetry service providers are currently approved in Canada:

They offer whole-body and extremity thermo-luminescent dosimetry services (TLD). Monitoring periods are usually quarterly but more frequent monitoring is also available for pregnant workers. In cases where the dose limits are exceeded, the client is notified. 


WorkSafeBC (WSBC) requires that: “Unless exempted by the Board, if a worker exceeds or may exceed the action level (1 mSv/y), the employer must ensure that the worker is provided with and properly uses an acceptable personal dosimeter”. It further requires that the employer must ensure that every worker who exceeds, or may exceed, the action level is fully informed of any potential reproductive hazards associated with radiation exposure. The Canadian Nuclear Safety Commission, on the other hand, requires that if there is reasonable probability that a worker who, by the nature of his/her work involving nuclear substances, may exceed the dose limit for the public of 1 mSv/y, should be informed of the risks of radiation exposure and be considered as a Nuclear Energy Worker (NEW).

 

The basic steps to reduce exposure to radiation are:

  • minimize time exposed to the radiation-emitting device or source to as short as possible;
  • increase distance from the radiation-emitting device or source to as far as practicable;
  • wear protective items that provide effective shielding such as lead aprons, thyroid collars, and gauntlets.

More information about lead aprons is provided in RIN 10 - Proper Selection, Care, Quality Control and Disposal of Lead Aprons. Protective items should be checked regularly for defects, cracks or holes because the level of protection provided by these items can be compromised by such defects. Guidance on when to reject defective aprons and other lead apparel is provided in a BCCDC 2003 Report entitled Rejection Criteria for Defects in Lead Apparel Used for Radiation Protection of X-ray Workers. Facility owners can choose to establish a more restrictive criteria as may be appropriate to their circumstances.

 
SOURCE: Protection of Workers and Patients in Radiology ( )
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