Radiation exposure to patients is kept “as low as reasonably achievable (ALARA)”
- Radiation used in medicine accounts for more than 90% of the total man-made radiation dose to the general population1.
- In general, the benefits of administering ionizing radiation for imaging and therapeutic purposes outweigh the risks (which refers to possible long-term or short-term effects) as long as radiation protection/safety guidelines are adhered to2.
- The aim of radiation protection, according to the International Commission on Radiation Protection is to “Contribute to an appropriate level of protection for people and the environment against the detrimental effects of radiation exposure without unduly limiting the desirable human actions that may be associated with such exposure”3
- The ALARA (As Low As Reasonably Achievable) principle is the philosophy that radiation dose should be managed in order to obtain the required medical images or therapy while minimizing the detrimental effects of radiation4.
- The ALARA principle is based on a non-threshold model, meaning that any level of radiation, no matter how small, has the potential of producing a biological effect.
- MRTs must always make an effort to keep radiation doses to a minimum while maintaining quality.
- Managing patient radiation dose involves many factors that differ by discipline and procedure5,6.
- Some important common factors include5,6:
- Source of radiation
- Length of exposure
- Distance from the source of radiation
- Technical parameters
- The ALARA principle is used when judging the appropriateness of an imaging procedure, or planning for radiation therapy treatments7:
- Use of radiation is optimized to obtain maximum benefit with the minimum of exposure
- Relative risks and benefits are weighed against feasible alternatives – modalities that do not use ionizing radiation are considered to limit patient exposure to radiation
- MRTs are responsible for quality control and proper preparation which will help minimize repeat procedures, for example:
- Images that are diagnostic, with clearly identifiable pathology, should not be repeated because of suboptimal image quality
- If there is uncertainty about the need for a repeat procedure, a radiologist or a more experienced MRT is consulted
- Proper quality control of the equipment and, in the case of nuclear medicine, of the radiopharmaceutical is assured prior to undertaking the procedure
- Appropriate instructions are given to the patient prior to and following procedure/treatment
- MRTs are responsible for determining the need for additional radiation safety actions before a radiation exposure, for example8:
- Recognition of patients and/or body parts that require special protection because of higher sensitivity to radiation
- Potential for devices (e.g., implanted cardiac devices) which may be in the proximity of the radiation field
- Use of appropriate scanning borders (taking into account the patients’ histological diagnosis) when performing CT simulation
- Proper documentation helps to ensure that diagnostic examinations are preserved for future use, circumventing the need for a repeat investigation.
- Technical parameters to further reduce doses include1:
- Filtration of low energy radiation
- Collimation of beams
- Selection of automatic exposure control (AEC) sensors
- Shielding (when appropriate)
- Appropriate focal spot-to-skin distance
- Adaptation of technique for children and different body types
- MRTs can consult with their radiation safety/protection officer for additional information.
Health Canada. Safety Code 35: Safety Procedures for the Installation, Use and Control of X-ray Equipment in Large Medical Radiological Facilities. Available from: http://www.hc-sc.gc.ca/ewh-semt/pubs/radiation/safety-code_35-securite/index-eng.php. [Accessed 12 Dec 2019]
Hall EJ, Giaccia AJ, eds. Radiobiology for the Radiologist. 8th ed. Philadelphia, PA: Lipincott, Wolters Kluwer; 2018.
International Commission on Radiological Protection. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37 (2-4).
Statkiewicz Sherer MA, Visconti P, Ritenour ER, et al. Radiation Protection in Medical Radiography. 7th ed. Maryland Heights, MO: Mosby Elsevier, 2013.
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.
Reynolds A. Patient-centered care. Radiol Technol 2009;81(2):133–147.
Canadian Association of Radiologists. 2012 CAR Diagnostic Imaging Referral Guidelines. Available from: https://car.ca/patient-care/referral-guidelines/. [Accessed 12 Dec 2018]
Amis ES, et al. American College of Radiology White Paper on Radiation Dose in Medicine. J Am Coll Radiol 2007;4:272-284.