McCollough Cynthia H, Ulzheimer Stefan, Halliburton Sandra S, Shanneik Kaiss, White Richard D, Kalender Willi A
Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
Radiology. 2007 May;243(2):527-38. doi: 10.1148/radiol.2432050808.
To develop a consensus standard for quantification of coronary artery calcium (CAC).
A standard for CAC quantification was developed by a multi-institutional, multimanufacturer international consortium of cardiac radiologists, medical physicists, and industry representatives. This report specifically describes the standardization of scan acquisition and reconstruction parameters, the use of patient size-specific tube current values to achieve a prescribed image noise, and the use of the calcium mass score to eliminate scanner- and patient size-based variations. An anthropomorphic phantom containing calibration inserts and additional phantom rings were used to simulate small, medium-size, and large patients. The three phantoms were scanned by using the recommended protocols for various computed tomography (CT) systems to determine the calibration factors that relate measured CT numbers to calcium hydroxyapatite density and to determine the tube current values that yield comparable noise values. Calculation of the calcium mass score was standardized, and the variance in Agatston, volume, and mass scores was compared among CT systems.
Use of the recommended scanning parameters resulted in similar noise for small, medium-size, and large phantoms with all multi-detector row CT scanners. Volume scores had greater interscanner variance than did Agatston and calcium mass scores. Use of a fixed calcium hydroxyapatite density threshold (100 mg/cm(3)), as compared with use of a fixed CT number threshold (130 HU), reduced interscanner variability in Agatston and calcium mass scores. With use of a density segmentation threshold, the calcium mass score had the smallest variance as a function of patient size.
Standardized quantification of CAC yielded comparable image noise, spatial resolution, and mass scores among different patient sizes and different CT systems and facilitated reduced radiation dose for small and medium-size patients.
制定冠状动脉钙化（CAC）定量分析的共识标准。
由心脏放射科医生、医学物理学家和行业代表组成的多机构、多制造商国际联盟制定了CAC定量分析标准。本报告具体描述了扫描采集和重建参数的标准化、使用特定患者体型的管电流值以达到规定的图像噪声，以及使用钙质量分数来消除基于扫描仪和患者体型的差异。使用包含校准插入物和额外体模环的仿真人体体模来模拟小、中、大三种体型的患者。使用推荐的方案对三种体模进行扫描，以确定不同计算机断层扫描（CT）系统的校准因子，这些因子将测量的CT值与羟基磷灰石钙密度相关联，并确定能产生可比噪声值的管电流值。钙质量分数的计算实现了标准化，并比较了不同CT系统间阿加斯顿积分、容积积分和质量积分的差异。
对于所有多排探测器CT扫描仪，使用推荐的扫描参数后，小、中、大体模的噪声相似。容积积分的扫描仪间差异比阿加斯顿积分和钙质量积分更大。与使用固定CT值阈值（130 HU）相比，使用固定的羟基磷灰石钙密度阈值（100 mg/cm³）可降低阿加斯顿积分和钙质量积分的扫描仪间变异性。使用密度分割阈值时，钙质量积分随患者体型的变化方差最小。
标准化的CAC定量分析在不同患者体型和不同CT系统间产生了可比的图像噪声、空间分辨率和质量积分，并有助于降低小体型和中等体型患者的辐射剂量。
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