The fisherman's cards: how to address past and future radiation exposures in clinical decision making

Accounting for radiation exposure from previous CT exams while deciding on the next exam: What do referring clinicians think?

PURPOSE

To obtain clinicians' views of the need to account for radiation exposure from previous CT scans and the advisability of a regulatory mechanism to control the number of CT scans for an individual patient.

METHODS

A convenience survey was conducted by emailing a link to a three-question electronic survey to clinicians in many countries, mostly through radiology and radiation protection contacts.

RESULTS

505 responses were received from 24 countries. 293 respondents (58%) understand that current regulations do not limit the number of CT scans that can be prescribed for a single patient in a year. When asked whether there should be a regulation to limit the number of CT scans that can be prescribed for a single patient in one year, only a small fraction (143, 28%) answered 'No', 182 (36%) answered 'Maybe' and 166 (33%) answered 'Yes'. Most respondents (337; 67%) think that radiation risk should form part of the consideration when deciding whether to request a CT exam. A minority (138; 27%) think the decision should be based only on the medical indication for the CT exam. Comparison among the 4 countries (South Korea, Hungary, USA and Canada) with the largest number of respondents indicated wide variations in responses.

CONCLUSIONS

A majority of the surveyed clinicians consider radiation risk, in addition to clinical factors, when prescribing CT exams. Most respondents are in favor of, or would consider, regulation to control the number of CT scans that could be performed on a patient annually.

Radiation risk issues in recurrent imaging

Millions of patients benefit from medical imaging every single day. However, we have entered an unprecedented era in imaging practices wherein 1 out of 125 patients can be exposed to effective dose >50 mSv from a single CT exam and 3 out of 10,000 patients undergoing CT exams could potentially receive cumulative effective doses > 100 mSv in a single day. Recurrent imaging with CT, fluoroscopically guided interventions, and hybrid imaging modalities such as positron emission tomography/computed tomography (PET/CT) is more prevalent today than ever before. Presently, we do not know the cumulative doses that patients may be receiving across all imaging modalities combined. Furthermore, patients with diseases with longer life expectancies are being exposed to high doses of radiation enabling radiation effects to manifest over a longer time period. The emphasis in the past on improving justification of imaging and optimization of technique and practice has proved useful. While that must continue, the current situation requires imaging device manufacturers to urgently develop imaging technologies that are safer for patients as high doses have been observed in patients where imaging has been justified through clinical decision-support and optimized by keeping doses below the national benchmark doses. There is a need to have a critical look at the fundamental principles of radiation protection as cumulative doses are likely to increase in the coming years.

Radiation concerns in frequent flyer patients: Should imaging history influence decisions about recurrent imaging?

Radiation risks from diagnostic imaging have captured the attention of patients and medical practitioners alike, yet it remains unclear how these considerations can best be incorporated into clinical decision making. This manuscript presents a framework to consider these issues in a potentially at-risk population, the so called "frequent flyer" patients undergoing a large amount of recurrent imaging over time. Radiation risks from the low-dose exposures of diagnostic imaging are briefly reviewed, as applied to recurrent exposures. Some scenarios are then explored in which it may be helpful to incorporate knowledge of a patient's imaging history. There is no simple or uniformly applicable approach to these challenging and often nuanced clinical decisions. The complexity and variability of the underlying disease states and trajectories argues against alerting mechanisms based on a simple cumulative dose threshold. Awareness of imaging history may instead be beneficial in encouraging physicians and patients to take the long view, and to identify those populations of frequent flyers that might benefit from alternative imaging strategies.

Paediatric lung imaging: the times they are a-changin'

Until recently, functional tests were the most important tools for the diagnosis and monitoring of lung diseases in the paediatric population. Chest imaging has gained considerable importance for paediatric pulmonology as a diagnostic and monitoring tool to evaluate lung structure over the past decade. Since January 2016, a large number of papers have been published on innovations in chest computed tomography (CT) and/or magnetic resonance imaging (MRI) technology, acquisition techniques, image analysis strategies and their application in different disease areas. Together, these papers underline the importance and potential of chest imaging and image analysis for today's paediatric pulmonology practice. The focus of this review is chest CT and MRI, as these are, and will be, the modalities that will be increasingly used by most practices. Special attention is given to standardisation of image acquisition, image analysis and novel applications in chest MRI. The publications discussed underline the need for the paediatric pulmonology community to implement and integrate state-of-the-art imaging and image analysis modalities into their structure-function laboratory for the benefit of their patients.

From 'Image Gently' to image intelligently: a personalized perspective on diagnostic radiation risk

The risk of ionizing radiation from diagnostic imaging has been a popular topic in the radiology literature and lay press. Communicating the magnitude of risk to patients and caregivers is problematic because of the uncertainty in estimates derived principally from epidemiological studies of large populations, and alternative approaches are needed to provide a scientific basis for personalized risk estimates. The underlying patient disease and life expectancy greatly influence risk projections. Research into the biological mechanisms of radiation-induced DNA damage and repair challenges the linear no-threshold dose-response assumption and reveals that individuals vary in sensitivity to radiation. Studies of decision-making psychology show that individuals are highly susceptible to irrational biases when judging risks. Truly informed medical decision-making that respects patient autonomy requires appropriate framing of radiation risks in perspective with other risks and with the benefits of imaging. To follow the principles of personalized medicine and treat patients according to their specific phenotypic and personality profiles, diagnostic imaging should optimally be tailored not only to patient size, body region and clinical indication, but also to underlying disease conditions, radio-sensitivity and risk perception and preferences that vary among individuals.

Prioritizing examination-centered over patient-centered dose reduction: a hazard of institutional "benchmarking"

OBJECTIVE

The purpose of this article is to evaluate whether examination-specific radiation dose metrics reliably measure an institution's success in reducing cancer risks.

MATERIALS AND METHODS

We projected health benefits from dose-reduction programs in a hypothetical institution that sought to decrease exposures from abdominopelvic CT. Using modeling techniques to project radiation-induced cancer risks and tertiary center data to inform the institution's abdominopelvic CT age distribution, we compared a program in which effective doses were reduced equally (from 10 to 7 mSv) across all scans with programs in which dose reduction was age dependent. For each program, we projected lethal cancers averted, life expectancy gained, and average institutional dose achieved. Markov Chain Monte Carlo methods were used to estimate uncertainty in projections.

RESULTS

The analysis's age distribution drew from 20,979 CT scans; 39% were from patients 65 years old and older. To illustrate trends yielded, if all patients in the hypothetical institution underwent 7-mSv (instead of 10-mSv) scans, we projected the maximum number of lethal cancers averted to be seven per 100,000 patients, and maximum life expectancy gained to be 0.26 days per patient, when averaged over the institution's population. When restricting dose reduction (from 10 to 7 mSv) to patients younger than 65 years, benefits were slightly lower (five lethal cancers averted per 100,000 patients and 0.22 days per patient gained); however, the average institutional dose was substantially higher (8.2 mSv). Although dose reduction in patients 65 years old and older accounted for only 16% of possible institutional life expectancy gains, this patient group contributed disproportionately (39%) to the institution's average dose.

CONCLUSION

Institutional examination-specific dose metrics can be misleading, because the least-benefited patients may contribute disproportionately toward "improved" averages.