02.02.06. Minimizing patient exposure
Ionizing radiation exposure to patients is kept “as low as reasonably achievable (ALARA)”
Risks of radiation
- Ionizing radiation used in medicine accounts for more than 90% of the total human-made radiation dose to the general population.1
- In general, the benefits of administering ionizing radiation for imaging and therapeutic purposes outweigh the risks, as long as radiation protection/safety guidelines are adhered to.2
- The benefit of administering ionizing radiation in medical imaging includes diagnosis or monitoring of a condition, and for therapeutic purposes.3,4
- The short-term risk of high doses of ionizing radiation is a tissue reaction. The long-term risks of ionizing radiation are carcinogenesis and heritable effects.3,4
- 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” (paragraph 26).5
- The ALARA 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 radiation.6
- 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 make an effort to keep radiation doses to a minimum while maintaining quality, every time.
Minimizing dose
- MRTs are responsible for taking steps to minimize ionizing radiation exposure to patients.7
- Managing patient radiation dose involves many factors that differ by discipline and procedure. Some important common factors include8,9:
- source of radiation,
- length of exposure,
- distance from the source of radiation, and
- other technical parameters.
- The ALARA principle is used when judging the appropriateness of an imaging procedure or planning for radiation therapy treatments10:
- 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;
- referral guidelines and recommendations such as those from Choosing Wisely Canada should be used to help determine imaging study appropriateness.10–13
- MRTs are responsible for quality control and proper preparation which will help minimize repeat procedures,7 for example:
- Images that are diagnostic, with clearly identifiable pathology, should not be repeated because of suboptimal image quality.14
- If there is uncertainty about the need for a repeat procedure, a radiologist or a knowledgeable MRT should be consulted.14
- 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 to be given to the patient prior to and following procedure/treatment.15
- MRTs are responsible for determining the need for additional radiation safety actions before a radiation exposure, for example16,17:
- recognition of patients and/or body parts that require special protection because of higher sensitivity to radiation;
- potential for radiosensitive devices (e.g., implanted cardiac devices) that 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.18,19
- Technical parameters to further reduce doses include1:
- filtration of low energy radiation;
- collimation of beams;
- use of dose-reduction technologies such as automatic exposure control (AEC) in radiography or dose-modulation in computed tomography20–22;
- appropriate focal spot-to-skin distance; and
- adaptation of technique for children and different body types.
- MRTs should consult their radiation safety/protection officer if they require additional information.
References
- Health Canada. Safety code 35: Safety procedures for the installation, use and control of x-ray equipment in large medical radiological facilities. Published online 2008. Accessed August 7, 2020. https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radiation/safety-code-35-safety-procedures-installation-use-control-equipment-large-medical-radiological-facilities-safety-code.html
- Hall EJ, Giaccia AJ. Radiobiology for the radiologist. 8th ed. Lippincott, Williams & Wilkins; 2018. Accessed August 7, 2020. https://shop.lww.com/Radiobiology-for-the-Radiologist/p/9781496335418
- Peck DJ, Samei E. How to understand and communicate radiation risk. Image Wisely. Published March 2017. Accessed August 27, 2020. https://www.imagewisely.org/Imaging-Modalities/Computed-Tomography/How-to-Understand-and-Communicate-Radiation-Risk
- Balter S, Miller DL. Patient skin reactions from interventional fluoroscopy procedures. Am J Roentgenol. 2014;202(4):W335-W342. doi:10.2214/AJR.13.12029
- ICRP. The 2007 recommendations of the International Commission on Radiological Protection. ICRP publication 103. Ann ICRP. 2007;37(2-4):1-332. doi:10.1016/j.icrp.2007.10.003
- Statkiewicz Sherer MA, Visconti P, Ritenour ER, Welch Haynes K. Radiation protection in medical radiography. 7th ed. Mosby Elsevier; 2015. Accessed August 7, 2020. https://www.elsevier.com/books/radiation-protection-in-medical-radiography/statkiewicz-sherer/978-0-323-17220-2
- Canadian Association of Medical Radiation Technologists. Member code of ethics and professional conduct. CAMRT. Published November 2015. Accessed June 23, 2020. https://www.camrt.ca/mrt-profession/professional-resources/code-of-ethics/
- 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. Pediatr Radiol. 2006;36(Suppl 2):110-112. doi:10.1007/s00247-006-0184-4
- Reynolds A. Patient-centered care. Radiol Technol. 2009;81(2):133-147.
- Canadian Association of Radiologists. 2012 CAR diagnostic imaging referral guidelines. Canadian Association of Radiologists. Published 2012. Accessed August 7, 2020. https://car.ca/patient-care/referral-guidelines/
- Canadian Association of Medical Radiation Technologists. Five things medical radiation technologists and patients should question. Choosing Wisely Canada. Published December 2018. Accessed August 27, 2020. https://choosingwiselycanada.org/medical-radiation-technology/
- Canadian Association of Nuclear Medicine. Five tests, treatments to question in nuclear medicine. Choosing Wisely Canada. Published February 2020. Accessed August 27, 2020. https://choosingwiselycanada.org/nuclear-medicine/
- Canadian Association of Radiologists. Five things physicians and patients should question in radiology. Choosing Wisely Canada. Published February 2020. Accessed August 27, 2020. https://choosingwiselycanada.org/radiology/
- Rosenkrantz AB, Fleishon HB, Hudgins PA, Bender CE, Duszak RJ. Characteristics of radiologists’ clinical practice patterns by career stage. Acad Radiol. 2020;27(2):262-268. doi:10.1016/j.acra.2019.03.025
- Pollard N, Lincoln M, Nisbet G, Penman M. Patient perceptions of communication with diagnostic radiographers. Radiography. 2019;25(4):333-338. doi:10.1016/j.radi.2019.04.002
- Amis ES, Butler PF, Applegate KE, et al. American College of Radiology white paper on radiation dose in medicine. J Am Coll Radiol JACR. 2007;4(5):272-284. doi:10.1016/j.jacr.2007.03.002
- Amis ES, Butler PF, American College of Radiology. ACR white paper on radiation dose in medicine: Three years later. J Am Coll Radiol JACR. 2010;7(11):865-870. doi:10.1016/j.jacr.2010.04.006
- Janiak BD, Rawson JV, Clayton SK. Unnecessary repeat radiologic examinations in the emergency department after interfacility transfer. J Am Coll Radiol. 2015;12(10):1079-1081. doi:10.1016/j.jacr.2015.05.015
- Center for Devices and Radiological Health. White paper: Initiative to reduce unnecessary radiation exposure from medical imaging. Published online February 2010. Accessed August 27, 2020. https://www.fda.gov/radiation-emitting-products/initiative-reduce-unnecessary-radiation-exposure-medical-imaging/white-paper-initiative-reduce-unnecessary-radiation-exposure-medical-imaging
- Lee RK, Sun JY, Lockerby S, Soltycki E, Matalon T. Reducing variability of radiation dose in CT: The new frontier in patient safety. J Am Coll Radiol. 2018;15(11):1633-1641. doi:10.1016/j.jacr.2017.10.009
- Dixon MT, Loader RJ, Stevens GC, Rowles NP. An evaluation of organ dose modulation on a GE optima CT660‐computed tomography scanner. J Appl Clin Med Phys. 2016;17(3):380-391. doi:10.1120/jacmp.v17i3.5724
- Ota J, Yokota H, Takishima H, et al. Breast exposure reduction using organ-effective modulation on chest CT in Asian women. Eur J Radiol. 2019;119:108651. doi:10.1016/j.ejrad.2019.108651
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