Sven A. Holcombe, Steven R. Horbal, Brian E. Ross, Edward Brown, Brian A. Derstine, Stewart C. Wang
Abstract
CT contrast media improves vessel visualization but can also confound calcification measurements. We evaluated variance in aorta attenuation from varied contrast-enhancement scans, and quantified expected plaque detection errors when thresholding for calcification.
Introduction
Cardiovascular disease remains the leading cause of death in the United States [1]. Approximately 50% of these deaths have no prior clinical symptoms or diagnoses [1, 2]. Abdominal aortic calcification shows strong promise as a clinical correlate and an effective predictive tool of future cardiovascular events [3–7]. Early risk identification is important to discern the type and intensity of preventative interventions; 50–90% of cardiovascular events are estimated to be preventable [8, 9]. Coronary artery calcium (CAC) scores paired with cardiovascular risk scores have traditionally provided the strongest estimates for cardiovascular event risk, however, performing coronary calcium scoring in asymptomatic individuals is not encouraged [2, 10].
Materials and methods
The CT scans used in this study were obtained from Michigan Medicine, investigation and analysis has Institutional Review Board approval (HUM-00041441). All data was anonymized prior to review and informed consent was waived due to the retrospective nature of the data. All image processing and data analysis was performed in MATLAB [18].
Results
Aorta CT attenuation
Distributions in aorta attenuation (mean AoHU from the L1 vertebral level) separated by sex and cohort are summarized in Fig 4. Other vertebral levels L4 through T9 showed similar distributions. Mean AoHU for females was significantly higher than for males in all contrast-enhanced cohorts (p < 0.001 in all comparisons). On average, female mean AoHU was higher by 20 HU in delayed-phase scans, 22 HU in venous scans, 48 HU to 65 HU in arterial scans, and 27 HU to 28 HU in the mixed-enhancement trauma scans.
Discussion
This analysis evaluated the central vessel HU in multiple large cohorts of aortas scanned with varying degrees of contrast-enhancement. The first of two main findings is that female aortas were consistently enhanced to higher radiodensities than their male counterparts, independent from subject body size. The second finding is that the variation in density introduced from contrast enhancement makes detection of plaque content via uniform HU thresholds an untenable general technique; dynamic thresholds calculated from local aorta content are more robust to scan variation.
Conclusion
In summary, we have reported distributions of aorta attenuation in different clinical CT scans exhibiting a wide range of contrast-material enhancement, and highlighted a sex-based difference which may bias downstream calcification scoring. To inform future efforts in automatic calcification scoring algorithms, we also report the plaque detection error rates across the range of contrast-enhanced scan protocols that might be expected under uniform and dynamic HU thresholding schemes.
Citation: Holcombe SA, Horbal SR, Ross BE, Brown E, Derstine BA, Wang SC (2022) Variation in aorta attenuation in contrast-enhanced CT and its implications for calcification thresholds. PLoS ONE 17(11): e0277111. https://doi.org/10.1371/journal.pone.0277111
Editor: Helmut Schoellnast, LKH Graz II Standort West: Landeskrankenhaus Standort West, AUSTRIA
Received: June 30, 2022; Accepted: October 20, 2022; Published: November 10, 2022
Copyright: © 2022 Holcombe et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: Dataset utilized is included in the paper and its Supporting information file.
Funding: The author(s) received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
