Medical imaging with computed tomography (CT) is an increasing source of population exposure to ionizing radiation, and a growing body of evidence, including the large study by Bastiani et al,1 indicates that patients have limited understanding about imaging, wish to be informed of the risks, but frequently are not.
Although CT provides considerable benefits in some settings, there is also broad agreement that it is frequently overused. Neck and back pain, headache, and suspected pulmonary embolism are but a few indications in which CT overuse has been highlighted. Not only do rates of CT imaging remain high despite efforts to control inappropriate use, but there is also troubling growth of imaging in patients with minor and less severe disease where the benefits are least likely to outweigh potential harms. Unindicated use of cervical spine imaging for minor injuries, for example, is substantially increasing emergency spine imaging.
The overuse of CT is a complex, multifaceted problem, associated in part with medical uncertainty, fear of malpractice, the near ubiquity of CT machines (which influences use to amortize their cost), and strong patient demand. However, a large part of the problem is a general misconception among patients and physicians that imaging with CT is mostly harmless, resulting in its unchecked growth. For physicians, the carcinogenic risk of cancer that may occur decades after exposure may seem so remote, it is easy for the immediate potential benefit of CT to eclipse thorough consideration of necessity. Yet overuse in diagnostic testing may bear near-term harms: too often giving false-positive results that may lead to a cascade of further testing, overdiagnosis resulting in unnecessary treatments, and time that could be spent on more meaningful treatments.2 These risks are not simple to understand or to explain to patients in the limited time clinicians have for consultation.
Moreover, extensive epidemiological and biological evidence suggest that exposure to radiation in the same range as that routinely delivered by CT increases a person's risk of developing cancer. In a recent systematic review and meta-analysis, Hauptmann et al3 observed excess cancer risks from low-dose ionizing radiation in the same dose range used in medical imaging, and the magnitude of cancer risks from these low-dose exposures was statistically comparable with the radiation dose-related cancer risks of atomic bomb survivors. A more recent systematic review reported an excess relative risk of cancer associated with CT exposures in childhood, finding that, for a CT examination delivering 10 mGy to the red bone marrow, leukemia risk increases by approximately 27%.4 In 2017, this was the average bone marrow exposure of 1 CT in a child and just slightly above the average bone marrow dose for an abdomen CT in an adult (R.S.-B., unpublished data, 2017). All told, exposure to CT is estimated to cause over 2% of cancers diagnosed annually in the US; in 2019 that would amount to 36 000 new cancers resulting from CT.5 In addition, with little standardization in practice, variation in radiation dose is a troubling phenomenon, with observed doses ranging widely across facilities for patients imaged for the same clinical reason.
It is in this context that the results of Bastiani et al1 should be understood. Motivated by the European Council Directive 2013/59/Euratom, which implemented legal requirements for justification and optimization in medical imaging, Bastiani et al conducted a multicenter, cross-sectional survey to assess patients’ knowledge of the risks of medical radiation, revealing “a lack of knowledge” regarding even basic radiation protection issues. Consistent with a growing body of evidence on these topics, a third of respondents could not identify CT as a radiation-based modality, and more than half did not know that chest CT delivers more radiation than chest radiography: the relative radiation dose is around 100 times higher. More poignantly, 44% of respondents believed their own knowledge of radiation risks was inadequate, and more than half received no information about risks before undergoing their examination. Although a higher educational level was modestly associated with greater knowledge, overwhelmingly, the study lines up with numerous others in depicting unsatisfactory awareness about medical imaging, which has not changed over the past 10 years.
Misunderstanding the potential harms of imaging hurts patients because they cannot appropriately balance the risks and benefits and engage knowledgably in their care. A patient-centered care approach would oblige health care clinicians, at a minimum, to disclose information on the risks, benefits, and alternatives to radiation-based imaging. It is not the numerical details of this communication that are as important as sharing the fact that imaging with ionizing radiation carries the potential for benefits and harm akin to other medical procedures. More research is needed to understand how best to communicate risks to patients, but withholding information should not be an option.
Patients frequently want to hear about risks from their referring physician, but often these clinicians do not possess adequate knowledge of the risks of specific imaging tests and how they relate to lifetime risk of cancer. In a survey of radiation knowledge among physicians from obstetrics, gynecology, family practice, emergency, and internal medicine, Hobbs et al6 found relatively low baseline knowledge across all specialties at all levels of training, including a quarter of respondents unable to identify which modalities involve ionizing radiation. This level of knowledge was statistically significantly improved following a brief educational presentation. Radiologists, on the other hand, generally have greater knowledge and training in the biological effects of radiation but have minimal interaction with patients.
It is the responsibility of clinicians who order tests to help patients make informed decisions about their health care. It is the responsibility of health leaders and systems to ensure ordering clinicians are equipped with the knowledge to do so. An American Board of Internal Medicine Foundation survey found 63% of physicians think they are in the best position to address the problem of unnecessary tests and procedures, and 92% think they have some responsibility for making sure patients avoid unnecessary care.7 If physicians do not have the requisite knowledge, they cannot meaningfully inform patients.
There is a role for radiologists. Shyu and Sodickson8 make a case for a collaborative relationship between radiologists and emergency department physicians where radiologists take on a direct consultative role; they may counsel ordering clinicians when imaging is not appropriate or when an alternative modality, such as ultrasonography, should be considered. Radiologists may directly inform patients of what strategies are in place to reduce excessive exposure while preserving diagnostic accuracy, and would also have to ensure such strategies exist at their institutions. Radiologists must also limit use of tests that have no value, perform examinations using radiation doses as low as reasonably achievable, and actively assess the doses that they use against benchmarks.
What is needed is a systemic and seismic shift in educating physicians and patients, in having candid conversations with patients around imaging that acknowledge the tradeoffs, and in justifying the use of all medical radiation exposure. In doing so, we improve the safety of medical imaging while reducing the physical, social, and economic toll of overuse and disease.
Published: October 13, 2021. doi:10.1001/jamanetworkopen.2021.29681
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Stewart C et al. JAMA Network Open.
Corresponding Author: Rebecca Smith-Bindman, MD, Department of Epidemiology and Biostatistics, University of California, San Francisco, 550 16th St, Box 0560, San Francisco, CA 94143 (email@example.com).
Conflict of Interest Disclosures: Dr Smith-Bindman is a founder of Alara Imaging, a company focused on collecting and reporting radiation dose information associated with computed tomography.
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