Abstract
The purpose of this study is to evaluate a direct measure of calcium burden by using dual‐energy computed tomography (DECT) during contrast‐enhanced coronary imaging, potentially eliminating the need for an extra noncontrast X‐ray acquisition. The ambiguity of separation of calcium from contrast material on contrast‐enhanced images was solved by using virtual noncontrast images obtained by DECT. A new threshold CT number was required to detect the calcium carrying potential risk for adverse coronary events on virtual noncontrast images. Two methods were investigated to determine the 130 HU threshold for DECT scoring. An in vitro anthropomorphic phantom with 29 excised patient calcium plaques inserted was used for both a linear and a logistic regression analysis. An IRB approved in vivo prospective study of six patients was also performed to be used for logistic regression analysis. The threshold found by logistic regression model to define the calcium burden on virtual noncontrast images detects the calcium carrying potential risk for adverse coronary events correctly (2.45% error rate). DECT calcium mass and volume scores obtained by using the threshold correlates with both conventional Agatston and volume scores (r=0.98,p<0.001). A conventional CT cardiac exam requires two scans, including a noncontrast scan for calcium quantification and a contrast‐enhanced scan for coronary angiography. With the ability to quantify calcium on DECT contrast‐enhanced images, a DECT cardiac exam could be accomplished with one contrast‐enhanced scan for both calcium quantification and coronary angiography.PACS numbers: 87.57.Q, 87.57.N
Highlights
204 Yamak et al.: Coronary calcium quantification suffer far less from the blooming artifact, so that large calcium plaques may not interfere with assessment of residual lumen
Noncontrast calcium images in which calcium content is preserved in the image. This approach may provide a measure of calcium plaque burden that is comparable to true noncontrast CAC scoring.[11]. The purpose of this study is to evaluate a direct measure of calcium burden by using
Equivalent 130 Hounsfield units (HU) threshold determination for Calcium(Iodine) image In the first method, the 29 ex vivo calcium plaques shown in Fig. 1 were used to compare conventional 120 kVp HU values with dual-energy computed tomography (DECT) calcium density measurements
Summary
204 Yamak et al.: Coronary calcium quantification suffer far less from the blooming artifact, so that large calcium plaques may not interfere with assessment of residual lumen. Patients needing evaluation for in-stent restenosis are difficult to visualize with conventional CCTA. The blooming artifact from stents can be removed with DECT (virtual nonstent images). The patient population for which CCTA is appropriate could potentially expand if the presence of stents or large amounts of calcium is no longer an impediment for DECT. Concern may exist for added radiation dose with DECT. A conventional CCTA coupled with noncontrast CACs is about 2.8mSv. A single fast-switched DECT is approximately the same at 2.7mSv without the extra noncontrast acquisition.[4] dose-neutral DECT total exam can possibly be achieved if the noncontrast exam can be eliminated
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