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Minimizing MRT exposure

 

Radiation exposure to MRTs is kept "as low as reasonably achievable (ALARA)"

 

+ Radiation limits

  • After extensive study of the deterministic and stochastic effects of radiation on the human body, the International Commission on Radiation Protection (ICRP) formed recommendations on dose limits for the people who work with radiation.1
  • In Canada, the Canadian Nuclear Safety Commission (CNSC) recommends dose limits for Nuclear Energy Workers (NEWs) and the provinces recommend doses for Radiation Workers.2
  • The effective dose limit for NEWs, as prescribed by the CNSC, is 100 mSv in 5 years (with a maximum of 50 mSv in any given year or an average of 20 mSv/yr for 5 years) for whole-body exposure.3-5
    • The cumulative lifetime dose should remain below 10 mSv multiplied by age3

  • The equivalent dose limit for Radiation Workers, as recommended by the ICRP (and Health Canada through Safety Code 35 ), is 20 mSv in a year for whole body exposure.6

+ Minimizing dose

  • The same factors that determine patient exposure to radiation apply for MRTs:3,7,8
    • Time of exposure (e.g., number of scans, time of exposure to the radioisotopes)
    • Distance from the source of radiation
    • Shielding with absorbent materials

 

  • The ALARA principle is used to guide the professional’s interaction with radiation:3,4
    • MRTs are aware of all possible sources of radiation in their environment –equipment (whether on or off), radiopharmaceuticals and patients
    • The least possible amount of time is spent in the proximity of a source of radiation
    • Immobilization devices should be used where possible, otherwise a family member or other healthcare professional may be asked to hold the patient
    • Shielding is used wherever possible, including mobile and stationary barriers, shielding garments and lead eye protection (or goggles)

 

  • MRTs likely to exceed a radiation dose of 1/20th of the recommended ICRP exposure limit are declared radiation workers and wear personal dosimeters to accurately monitor their exposure.4
  • Good planning and quality control can also help minimize exposure from certain sources of radiation.
    • CNSC regulations are followed for all components of construction or renovation of areas where radiation equipment will be placed9

+ References

  1. International Commission on Radiological Protection. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37 (2-4).
  2. Canadian Nuclear Safety Commission. Radiation Doses. Available at: http://nuclearsafety.gc.ca/eng/readingroom/radiation/radiation_doses.cfm. Accessed April 3, 2012.
  3. Adler AM, Carlton RR. Introduction to radiologic sciences and patient care. 3rd Ed. St. Louis, MO: Saunders; 2003.
  4. Health Canada. Safety Code 35: Safety Procedures for the Installation, Use and Control of X-ray Equipment in Large Medical Radiological Facilities. Available at: http://www.hc-sc.gc.ca/ewh-semt/pubs/radiation/safety-code_35-securite/section-a2-eng.php#a2.  Accessed May 31, 2012.
  5. Department of Justice Canada. Radiation Protection Regulations. Available at: http://laws-lois.justice.gc.ca/eng/regulations/SOR-2000-203/page-4.html#h-16 . Accessed May 30, 2012.
  6. Health Canada. Safety Code 35: Safety Procedures for the Installation, Use and Control of X-ray Equipment in Large Medical Radiological Facilities. Appendix 1: Dose Limits for Occupational Ionizing Radiation Exposures. Available at: http://www.hc-sc.gc.ca/ewh-semt/pubs/radiation/safety-code_35-securite/appendix-annexe-1-eng.php#app1.  Accessed May 31, 2012.
  7. Strauss KJ, Kaste SC. The ALARA (As Low As Reasonably Achievable) Concept in Pediatric Interventional and Fluoroscopic Imaging: Striving to Keep Radiation Doses as Low as Possible during Fluoroscopy of Pediatric Patients—A White Paper Executive Summary. Radiology 2006;240:621-622.
  8. Reynolds A. Patient-centered care. Radiol Technol 2009;81(2):133-147.
  9. Canadian Nuclear Safety Commission. GD-52: Design Guide for Nuclear Substance Laboratories and Nuclear Medicine Rooms. http://nuclearsafety.gc.ca/eng/lawsregs/guidancedocuments/published/html/gd52/index.cfm. Accessed April 3, 2012.

Related guidelines

>Personal protective equipment

 

 

Validation

June 1, 2012

 

 
Canadian Association of Medical Radiation Technologists
85 Albert St, Suite 1000, Ottawa, ON, K1P 6A4
phone: 613 234-0012 / 800 463-9729
fax: 613 234-1097
www.camrt.ca