US Food and Drug Administration, CDRH/OSEL/DIDSR, Silver Spring, MD, United States of America.
Phys Med Biol. 2018 Aug 30;63(17):175006. doi: 10.1088/1361-6560/aad9be.
Extracting coronary artery calcium (CAC) scores from contrast-enhanced computed tomography (CT) images using dual-energy (DE) based material decomposition has been shown feasible, mainly through patient studies. However, the quantitative performance of such DE-based CAC scores, particularly per stenosis, is underexamined due to lack of reference standard and repeated scans. In this work we conducted a comprehensive quantitative comparative analysis of CAC scores obtained with DE and compare to conventional unenhanced single-energy (SE) CT scans through phantom studies. Synthetic vessels filled with iodinated blood mimicking material and containing calcium stenoses of different sizes and densities were scanned with a third generation dual-source CT scanner in a chest phantom using a DE coronary CT angiography protocol with three exposures/CTDIvol: auto-mAs/8 mGy (automatic exposure), 160 mAs/20 mGy and 260 mAs/34 mGy and 10 repeats. As a control, a set of vessel phantoms without iodine was scanned using a standard SE CAC score protocol (3 mGy). Calcium volume, mass and Agatston scores were estimated for each stenosis. For DE dataset, image-based three-material decomposition was applied to remove iodine before scoring. Performance of DE-based calcium scores were analyzed on a per-stenosis level and compared to SE-based scores. There was excellent correlation between the DE- and SE-based scores (correlation coefficient r: 0.92-0.98). Percent bias for the calcium volume and mass scores varied as a function of stenosis size and density for both modalities. Precision (coefficient of variation) improved with larger and denser stenoses for both DE- and SE-based calcium scores. DE-based scores (20 mGy and 34 mGy) provided comparable per-stenosis precision to SE-based (3 mGy). Our findings suggest that on a per-stenosis level, DE-based CAC scores from contrast-enhanced CT images can achieve comparable quantification performance to conventional SE-based scores. However, DE-based CAC scoring required more dose compared with SE for high per-stenosis precision so some caution is necessary with clinical DE-based CAC scoring.
使用基于双能（DE）的物质分解从对比增强计算机断层扫描（CT）图像中提取冠状动脉钙（CAC）评分已经被证明是可行的，主要通过患者研究。然而，由于缺乏参考标准和重复扫描，基于 DE 的 CAC 评分的定量性能，特别是每个狭窄部位的定量性能，还没有得到充分的研究。在这项工作中，我们通过体模研究对基于 DE 的 CAC 评分与传统的非增强单能（SE）CT 扫描进行了全面的定量比较分析。使用第三代双源 CT 扫描仪，在胸部体模中，用 DE 冠状动脉 CT 血管造影方案以三种曝光/CTDIvol 扫描充满碘造影剂模拟物质的合成血管：自动 mAs/8 mGy（自动曝光）、160 mAs/20 mGy 和 260 mAs/34 mGy 和 10 次重复。作为对照，一组不含碘的血管体模使用标准 SE CAC 评分方案（3 mGy）进行扫描。为每个狭窄部位估计钙体积、质量和 Agatston 评分。对于 DE 数据集，在评分前应用基于图像的三物质分解去除碘。分析了基于 DE 的钙评分的性能，并与基于 SE 的评分进行了比较。DE 与 SE 评分之间存在极好的相关性（相关系数 r：0.92-0.98）。对于两种模态，钙体积和质量评分的百分比偏差随狭窄大小和密度而变化。对于基于 DE 和 SE 的钙评分，随着狭窄部位的增大和密度的增大，精度（变异系数）提高。DE 基评分（20 mGy 和 34 mGy）与 SE 基评分（3 mGy）相比，提供了相当的每个狭窄部位精度。我们的发现表明，在每个狭窄部位水平上，基于对比增强 CT 图像的 DE 基 CAC 评分可以达到与传统的基于 SE 的评分相当的定量性能。然而，与 SE 相比，基于 DE 的 CAC 评分需要更多的剂量才能达到高的每个狭窄部位精度，因此在进行基于 DE 的 CAC 评分时需要谨慎。
