Date of Award

January 2012

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Hamid R. Mojibian

Subject Area(s)

Medicine, Medical imaging and radiology

Abstract

Over the last decade, major advances in the performance of computed tomography (CT) have revolutionized the ability of radiologists to detect the subtlest subclinical manifestations of disease. One important element in the evaluation of these CT scans is the likelihood of so-called incidental findings (IFs), which are defined as an imaging abnormality not related to the original indication for obtaining the study. In the literature on IFs, many studies have looked at extra-cardiac IFs on cardiac CT imaging and concluded that the interpretation of these extra-cardiac findings on coronary CT angiography is mandatory given the high prevalence of clinically significant findings when using a full thoracic field of view. However, the converse idea has not been systematically studied: what is the prevalence and clinical significance of incidental cardiovascular findings on routine chest CT examinations?

There has been increasing interest in diagnosing cardiac and pericardial diseases using electrocardiogram (EKG) synchronized, or gated, cardiac CT, which adjusts for cardiac movement during image acquisition. But even with routine chest CT scans, which generally do not utilize EKG gating, many diseases of the heart can be seen. In this study, we retrospectively reviewed 445 non-EKG-gated, routine chest CT scans ordered for non-cardiac reasons and found that 67.0% had at least one incidental cardiovascular finding, with each study having an average of 3.8 IFs. We then classified each IF by their clinical significance, based on a thorough literature search, discussed in this thesis, exploring the possible prognostic implications for individual IFs. In comparing our independent findings with the original radiology reports, we found that while no emergent life-threatening findings were missed, 78.1% of unconditionally significant and 74.4% of conditionally significant IFs were unmentioned in the final reports. We propose several potential reasons for these low rates of reporting, including an unclear understanding among radiologists about the clinical utility of these IFs and inadequate cardiac imaging training for radiologists. The original study indication and patient comorbidities may also play a role, as studies performed in the Emergency Department, or for trauma or cancer staging, were associated with higher rates of unreported IFs.

Given the high prevalence of IFs, we recommend that radiologists consistently report all clinically significant incidental cardiovascular findings found on routine, non-EKG-gated chest CT scans. In turn, this leaves it to the ordering clinician to interpret these findings in the clinical context and ultimately decide whether or not to pursue further work-up. Although future studies need to be performed to further elucidate the diagnostic, prognostic, and economic implications for each IF on non-gated chest CT, this study seeks to encourage radiologists to be more aware of the vast cardiovascular findings that may be readily visualized on routine chest CT scans.

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