Introduction

Improvement in the diagnostic capabilities of cardiac imaging procedures has been paralleled by an increase in their utilization. The American College of Cardiology has developed appropriate use criteria as a guide for appropriate referral for testing to help maintain accountability among referring and laboratory physicians.^1,2 Moreover, numerous guidelines provide recommendations as to how to balance image quality and radiation dose in cardiac imaging.^3,4 Notwithstanding these efforts, there have been concerns that inappropriate use of these procedures and inconsistent adherence to best practices have led to unwarranted ionizing radiation exposure, with subsequent potential for cancer risk among those exposed. This has prompted an in-depth evaluation of current practice patterns to review the extent to which radiation safety principles, namely justification and optimization, are incorporated to achieve patient-centered imaging quality.⁵

Quality healthcare delivery is accomplished when providers offer services based on the highest level of scientific evidence, establishing a definitive benefit in patient-centered outcomes.⁶ The measured outcomes, as defined by the Institute of Medicine's report on health care quality, include safety, patient-centeredness, equity, effectiveness, efficiency, and timeliness,⁶ all of which contribute to patient-centered imaging. An additional key component in quality improvement is refraining from offering services that are likely to be of limited or no benefit; this principle highlights a self-evident but important issue that unwarranted tests have the potential to cause harm from procedural overuse.⁶ Ultimately, the objective of radiological protection as it pertains to cardiovascular imaging procedures is to ensure that patients receive the full benefits of imaging while patients and operators are protected against potential harms, including but not limited to ionizing radiation.⁵ This is reflected in the two principles of medical radiation safety: justification and optimization. Optimization refers to achieving both patient-centered and diagnostic procedural outcomes while minimizing harm to the patient and operator. Justification focuses on patient-centered outcomes by ensuring that a procedure is medically appropriate. As mentioned previously, the appropriate use criteria are the key tools utilized to not only prevent unnecessary procedures, but also establish a framework of appropriate referral patterns to minimize overall patient harm. Many of the issues herein—detailing the specifics of consolidating the approaches of optimization and justification—were addressed in a symposium sponsored by the National Institutes of Health National Heart, Lung, and Blood Institute and National Cancer Institute held at Emory University in November 2012.⁵

As illustrated in a 2013 study by Busey et al., most patients undergoing computed tomography (CT) imaging or single-photon emission CT (SPECT) imaging are unaware or inadequately informed of the potential risk of ionizing radiation.⁷ The responsibility to fully inform patients, based on consensus from prior symposia and statements from radiological protection organizations, has been directed to both the referring and laboratory physicians.⁵ There must be a shared accountability among these providers to educate the patient population and justify each individual procedure that involves ionizing radiation in order to facilitate patient decision-making.⁵

In the ideal scenario, both the referring provider and laboratory physician should possess adequate knowledge to discuss the risks and benefits of a particular imaging study with the patient. Practically, the responsibility of patient education should be distributed between the referring provider and imager. The referring provider best appreciates a patient's clinical situation and can better contextualize how an imaging procedure benefits the patient. At the time of test ordering, the patient should, according to his or her level of understanding and health literacy, be informed of both potential benefits and potential risks associated with the imaging procedure, the latter including the harms of misdiagnosis and of radiation. Alarmism should be eschewed. This early disclosure is important because the patient would likely have little context to incorporate the information into decision-making if this information were first presented upon arrival to an imaging laboratory.⁵ On the other hand, the imaging provider likely has a better grasp on the specific amount of radiation to which the patient will be exposed and its associated health risks. Consequently, one responsibility of the laboratory physician should be to educate the referring provider by offering educational materials to aid the benefit-risk discussion with patients, with information incorporating topics of procedural justification and dose optimization practice of the laboratory.⁸ Professional societies play an important role in the development of such materials. An open dialogue between providers and patients should be encouraged, with additional information in the form of booklets or online data provided for those who seek it.⁵

Communicating radiation-related health risks is a complex and challenging process for many reasons, such as limited patient health literacy and difficulty understanding risk-based decisions.^5,9 Therefore, effective communication strategies need to be explored in order for patients to utilize information about radiation exposure in a meaningful way. With regard to setting the premise of the discussion, providers must understand that concerns regarding radiation exposure are prevalent in the community and that patients have mixed feelings about this topic. They have both positive emotions, associated with benefits in terms of diagnosis and prognosis, as well as negative ones, such as the fear of possibility of cancer.⁵ Once these feelings are acknowledged by the providers, the discussion can then proceed.

There are a few key topics to cover with the patient in terms of communication content. First, patients should be alerted that a given imaging procedure exposes them to ionizing radiation. Second, expected radiation dose from a procedure should be qualitatively compared with other forms of radiation, such as yearly background radiation or chest x-rays, with potential for risk of cancer explained. There is evidence suggesting that patients have greater comprehension about their risks when they can make comparisons with common situations (e.g., risk of dying from a car accident). Subsequently, physicians should provide perspective on how a patient's risk of cancer changes after ionizing radiation in comparison with an everyday scenario. For example, a typical coronary CT angiography in many laboratories may deliver an effective dose of 10 mSv, for which an estimated risk of fatal malignancy equaling 0.5 in 1000 individuals has been ascribed.¹⁰ Such a risk estimate is crude and does not incorporate patient-specific factors such as age, gender, and comorbidities; however, it does provide a figure that is roughly only a third of the lifetime risk of dying from a pedestrian accident, which is 1.6 in 1000 individuals.¹⁰ Third, the patient should be made aware of the benefits of the procedure and, when practicable, how the benefit-risk assessment plays a role in clinical decision-making. Finally, in some cases it may be worthwhile to explore alternative management decisions with the patient, including tests with different benefit-risk calculus and the option of no testing at all. Strategies to facilitate communication can include visual aids with graphs and charts, which increase patient engagement. In addition, using the "teach-back" method¹¹ and "plain language"¹² are different communication tools that can aid patient understanding.¹³

The proposed communication strategies can be utilized by providers to guide patient decision-making for cardiac imaging procedures. The next step is to decide if formal disclosure, such as written informed consent, should be established as a part of this process. Currently, most institutions across the nation do not incorporate written informed consent or discussion of the radiation risks into their standard practice.^14-18 Fully discussing the merits and disadvantages of informed consent is beyond the scope of this article. However, at least initiating discussions with patients regarding radiation exposure is a step that promotes trust between patient and physician. And establishing trust will help rectify patient misunderstandings, lessen fears of the risks of ionizing radiation, and provide transparency in a collaborative decision-making process.⁵

Furthermore, patient-to-physician discussion or informed consent about radiation exposure may be guided by the threshold of the expected amount of ionizing radiation to which a patient will be exposed. Established tiers of radiation include 3 mSv (average annual background radiation level in the United States), 20 mSv (recommended average annual occupational dose limit for adults),¹⁹ and 50 mSv (the single-year occupational dose limit for adults).²⁰ The degree of radiation burden will aid the depth of discussion between the patient and physician because the radiation-attributable risk will depend on exposure level.

For patients receiving an effective dose expected to be less than 3 mSv for an imaging procedure, the Emory symposium participants suggested that harms of radiation do not need to be discussed extensively. Written material can be provided to the patient, detailing the low risk associated with the degree of exposure that equals the average annual background radiation in the United States. However, for procedures in which the effective radiation dose is expected to reach 20 mSv or more, a deeper discussion and/or written informed consent was recommended. There are several imaging protocols that exceed 20 mSv, including 120 kV, helical, low-pitch, retrospectively gated coronary CT angiography, and dual-isotope nuclear stress tests on SPECT cameras.^21-23 Before such a high-dose protocol is performed, a benefit-risk discussion with the patient is recommended. Establishing these radiation thresholds that trigger discussion and informed consent may help formalize the disclosure process across different institutions and patient populations and perhaps steer clinicians toward lower-dose procedures not mandating the more detailed discussion or consent. Additionally, this standardized patient-to-physician interaction will give the provider some additional time to reflect on clinical decision-making as it applies to the principle of justification to help avoid procedural overuse.

Although our discussion has focused on the adult patient, children with congenital and acquired heart disease represent a vulnerable population that requires specific mention, due both to the potential for multiple radiation-involving cardiac imaging procedures and to the increased longitudinal risk of radiation-associated malignancy in children.⁴ Application of the radiation safety principles of justification and optimization is especially of critical importance in children.⁴

There are numerous optimization strategies that have been proposed and implemented for cardiac CT and nuclear cardiac imaging. Specific methods include, for example, electrocardiogram-triggered prospective imaging and iterative reconstruction methods for cardiac CT and stress-only imaging and weight-based dosing in nuclear cardiology.⁴ Nevertheless, even when such methods are used to minimize radiation exposure, potential for harm still exists with every procedure. Several surveys have inquired whether parents of children undergoing such imaging procedures would want to know the risks, namely those of ionizing radiation. Notably, the clear majority preferred to be informed of these potential harms.^24,25 In light of this expressed preference, the decision-making process that incorporates a balance of benefits and risks should be clearly communicated and shared among the physician, the patient, and the patient's family when deemed appropriate. In adult cardiac imaging, there are recommended radiation dose thresholds that can be used to guide the extent of communication for verbal and/or written consent.⁴ Perhaps utilizing these dose thresholds as a frame of reference for pediatric patients as well could facilitate varying levels of communication between the patient and provider. When discussion with the patient's family occurs, both the justification for the procedure and efforts that would be made to optimize radiation dose should be explained insofar as possible, also reflecting the family's level of health literacy.

References

1. Hendel RC, Patel MR, Allen JM, et al. Appropriate use of cardiovascular technology: 2013 ACCF appropriate use criteria methodology update: a report of the American College of Cardiology Foundation appropriate use criteria task force. J Am Coll Cardiol 2013;61:1305-17.
2. Wolk MJ, Bailey SR, Doherty JU, et al. ACCF/AHA/ASE/ASNC/HFSA/HRS/SCAI/SCCT/SCMR/STS 2013 multimodality appropriate use criteria for the detection and risk assessment of stable ischemic heart disease: a report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and Society of Thoracic Surgeons. J Am Coll Cardiol 2014;63:380-406.
3. Fazel R, Gerber TC, Balter S, et al. Approaches to enhancing radiation safety in cardiovascular imaging: a scientific statement from the American Heart Association. Circulation 2014;130:1730-48.
4. Hill KD, Frush DP, Han BK, et al. Radiation Safety in Children With Congenital and Acquired Heart Disease: A Scientific Position Statement on Multimodality Dose Optimization From the Image Gently Alliance. JACC Cardiovasc Imaging 2017;10:797-818.
5. Einstein AJ, Berman DS, Min JK, et al. Patient-centered imaging: shared decision making for cardiac imaging procedures with exposure to ionizing radiation. J Am Coll Cardiol 2014;63:1480-9.
6. Institute of Medicine (US) Committee on Quality of Health Care in America. Crossing the Quality Chasm: A New Health System for the 21st Century. Washington (DC): National Academies Press; 2001.
7. Busey JM, Soine LA, Yager JR, Choi E, Shuman WP. Patient knowledge and understanding of radiation from diagnostic imaging. JAMA Intern Med 2013;173:239-41.
8. Fazel R, Dilsizian V, Einstein AJ, Ficaro EP, Henzlova M, Shaw LJ. Strategies for defining an optimal risk-benefit ratio for stress myocardial perfusion SPECT. J Nucl Cardiol 2011;18:385-92.
9. Tversky A, Kahneman D. Judgment under Uncertainty: Heuristics and Biases. Science 1974;185:1124-31.
10. Gerber TC, Carr JJ, Arai AE, et al. Ionizing radiation in cardiac imaging: a science advisory from the American Heart Association Committee on Cardiac Imaging of the Council on Clinical Cardiology and Committee on Cardiovascular Imaging and Intervention of the Council on Cardiovascular Radiology and Intervention. Circulation 2009;119:1056-65.
11. Federal Plain Language Guidelines (Plain Language Action and Information Network website). May 2011. Available at: http://www.plainlanguage.gov/howto/guidelines/FederalPLGuidelines/FederalPLGuidelines.pdf. Accessed 01/09/2018.
12. Health Literacy Universal Precautions Toolkit, Tool 5: The Teach-Back Method (North Carolina Program on Health Literacy website). 2014. Available at: http://www.nchealthliteracy.org/toolkit/tool5.pdf. Accessed 01/09/2018.
13. Schillinger D, Piette J, Grumbach K, et al. Closing the loop: physician communication with diabetic patients who have low health literacy. Arch Intern Med 2003;163:83-90.
14. National Research Council (US) Committee on Health Effects of Exposure to Low Levels of Ionizing Radiations (BEIR VII). Health Effects of Exposure to Low Levels of Ionizing Radiations: Time for Reassessment? Washington (DC): National Academies Press; 1998.
15. Baerlocher MO, Detsky AS. Discussing radiation risks associated with CT scans with patients. JAMA 2010;304:2170-1.
16. Brink JA, Goske MJ, Patti JA. Informed decision making trumps informed consent for medical imaging with ionizing radiation. Radiology 2012;262:11-4.
17. Semelka RC, Armao DM, Elias J Jr, Picano E. The information imperative: is it time for an informed consent process explaining the risks of medical radiation? Radiology 2012;262:15-8.
18. Paterick TE, Jan MF, Paterick ZR, Tajik AJ, Gerber TC. Cardiac imaging modalities with ionizing radiation: the role of informed consent. JACC Cardiovasc Imaging 2012;5:634-40.
19. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP publication 103. Ann ICRP 2007;37:1-332.
20. NRC Regulations 10 Code of Federal Regulations 20.1201 Subpart C--Occupational Dose Limits (United States Nuclear Regulatory Commission website). Available at: https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1201.html. Accessed 10/14/2017.
21. Cousins C, Miller DL, Bernardi G, et al. ICRP PUBLICATION 120: Radiological protection in cardiology. Ann ICRP 2013;42:1-125.
22. Halliburton SS, Abbara S, Chen MY, et al. SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT. J Cardiovasc Comput Tomogr 2011;5:198-224.
23. Einstein AJ, Moser KW, Thompson RC, Cerqueira MD, Henzlova MJ. Radiation dose to patients from cardiac diagnostic imaging. Circulation 2007;116:1290-305.
24. Boutis K, Cogollo W, Fischer J, Freedman SB, Ben David G, Thomas KE. Parental knowledge of potential cancer risks from exposure to computed tomography. Pediatrics 2013;132:305-11.
25. Larson DB, Rader SB, Forman HP, Fenton LZ. Informing parents about CT radiation exposure in children: it's OK to tell them. AJR Am J Roentgenol 2007;189:271-5.

Keywords: Background Radiation, Comorbidity, Angiography, Decision Making, Diagnostic Errors, Diagnostic Imaging, Electrocardiography, Exercise Test, Health Literacy, Heart Diseases, Informed Consent, Isotopes, National Cancer Institute (U.S.), Neoplasms, Patient Harm, Patient Participation, Patient Safety, Prospective Studies, Quality Improvement, Radiation Dosage, Radiation Protection, Radiation, Ionizing, Retrospective Studies, Risk Assessment, Cardiac-Gated Single-Photon Emission Computer-Assisted Tomography, Tomography, Emission-Computed, Single-Photon, Unnecessary Procedures, Vulnerable Populations, X-Rays

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