Scientific Session 29 — SS29: Cardiac Imaging - CTFriday, May 10, 2019
2742. Evaluation of Calcified Coronary Plaques: Optimal Monoenergetic Reconstruction and Window Presentation Settings
Chalian H1*, Richards T1, Khoshpouri P2, Samei E1 1. Duke University Medical Center, Durham, NC; 2. Johns Hopkins University School of Medicine, Baltimore, MD
Address correspondence to H. Chalian (Hamid.firstname.lastname@example.org)
Objective: Traditional polychromatic CT images suffer from calcium blooming artifacts, rendering the clinical evaluation of calcified coronary plaques difficult and variable. Furthermore, each radiologist’s or cardiologist’s attempt to mitigate this artifact through their choice of window presentation settings serves only to broaden the possible range of image interpretations and minimize the utility of disease staging within the CAD-RADS stenosis severity categories. The use of dual-energy derived monoenergetic image reconstructions may reduce the calcium blooming artifact and provide a platform for optimized evaluation of calcified coronary plaques. Our goal was to determine the utility and optimal combination of monoenergetic reconstruction and window presentation settings to achieve maximum separation, or disease staging specificity, between three CAD-RADS categories (25, 50, and 70% diameter stenosis) with 3D-printed coronary calcified plaques.
Materials and Methods: Plaque models with 25-70% stenosis were imaged on a dual-source CT (Siemens Force) under a dual-energy CCTA protocol, resulting in monoenergetic images from 70 to 120keV. Window settings were derived from mean HU values of the intraluminal-ROI for each monoenergetic image (WL=0.72x(HU) ¯lumen WW=2.07x(HU) ¯lumen). Two additional window selection methods were used by normalizing the presented image contrast and average image gradient. Four radiologists measured lumen diameter for all combinations of stenosis, energy, and window settings (63-images) by using custom image display software. Stenosis level separation was calculated as FOM=mean lumen diameter difference between successive stenosis levels divided by mean interobserver variability from each level.
Results: The monoenergetic reconstruction at 110 keV, presented with the intraluminal-derived window presentation settings (WL = 78 HU, WW = 224 HU) resulted in the best lumen stenosis level separation (FOM = 5.42). This combination of monoenergetic energy and window setting was 10% better than the traditional polychromatic images, and 72% better than the overall mean. Additionally, the intraluminal derived window presentation setting achieved the best average separation (FOM = 3.94) across all monoenergetic and polyenergetic images.
Conclusion: Dual-energy–derived monoenergetic images reduce calcium blooming. We found that this superior image quality only rendered improved stenosis level separation when paired with ideal window settings. The use of optimal monoenergetic reconstruction and window presentation settings in the clinical evaluation of calcified coronary plaques can result in improved specificity in disease staging (CAD-RADS) and more accurate progression monitoring.