Mergen Victor, Ried Emanuel, Allmendinger Thomas, Sartoretti Thomas, Higashigaito Kai, Manka Robert, Euler Andre, Alkadhi Hatem, Eberhard Matthias
Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland.
Siemens Healthcare, Forchheim, Germany.
AJR Am J Roentgenol. 2022 May;218(5):822-829. doi: 10.2214/AJR.21.26930. Epub 2021 Dec 8.
Epicardial adipose tissue (EAT) attenuation is a vascular inflammation marker predictive of adverse cardiac events. The fat attenuation index (FAI) assesses fat attenuation for predefined coronary segments. Photon-counting detector (PCD) CT uses routine virtual monoenergetic image (VMI) reconstructions. VMI energy level may affect EAT attenuation and FAI measurements. The purpose of this article was to assess EAT attenuation and FAI measurements at different monoenergetic energy levels in patients undergoing coronary CTA using a first-generation whole-body dual-source PCD CT scanner. An anthropomorphic phantom at two sizes with a fat insert was imaged on a first-generation dual-source PCD CT scanner and, as a reference, on a conventional energy-integrating detector (EID) CT scanner at 120 kV. Thirty patients (11 women, 19 men; mean age, 48 ± 10 years; Agatston score < 60) who underwent an ECG-gated unenhanced calcium-scoring scan and contrast-enhanced coronary CTA by PCD CT were retrospectively evaluated. VMIs from 55 to 80 keV at 5-keV increments were reconstructed. EAT attenuation was manually measured on unenhanced and contrast-enhanced images. FAI was calculated using semiautomated software. The attenuation of the phantom fat insert was -69 HU for the reference EID CT; the closest attenuation for PCD CT was observed at 70 keV for the small (-69 HU) and large (-70 HU) phantoms. In patients, EAT attenuation increased for unenhanced acquisition from -111 ± 11 HU at 55 keV to -82 ± 9 HU at 80 keV and for contrast-enhanced acquisition from -104 ± 11 HU at 55 keV to -81 ± 9 HU at 80 keV. The mean attenuation difference between unenhanced and contrast-enhanced scans decreased with increasing energy level (from 7 ± 12 HU to 1 ± 10 HU). The FAI increased from -89 ± 8 HU at 55 keV to -77 ± 12 HU at 80 keV for the right coronary artery, -95 ± 11 HU at 55 keV to -85 ± 11 HU at 80 keV for the left anterior descending artery, and -87 ± 10 HU at 55 keV to -80 ± 12 HU at 80 keV for the circumflex artery. EAT attenuation and FAI measurements using PCD CT are impacted by VMI energy level and contrast enhancement. Use of VMI reconstruction at 70 keV provides fat attenuation approximating conventional polychromatic measurements. The findings may help standardize evaluation of pericoronary inflammation by PCD CT as a measure of patients' cardiac risk.
心外膜脂肪组织（EAT）衰减是预测不良心脏事件的血管炎症标志物。脂肪衰减指数（FAI）用于评估预定义冠状动脉节段的脂肪衰减。光子计数探测器（PCD）CT使用常规虚拟单能量图像（VMI）重建。VMI能量水平可能会影响EAT衰减和FAI测量。本文的目的是使用第一代全身双源PCD CT扫描仪评估接受冠状动脉CTA检查的患者在不同单能量水平下的EAT衰减和FAI测量。在第一代双源PCD CT扫描仪上对带有脂肪插入物的两种尺寸的人体模型进行成像，并作为参考，在120 kV的传统能量积分探测器（EID）CT扫描仪上成像。回顾性评估了30例患者（11名女性，19名男性；平均年龄48±10岁；阿加斯顿评分<60），这些患者接受了心电图门控非增强钙评分扫描和PCD CT增强冠状动脉CTA检查。以5 keV增量重建55至80 keV的VMI。在非增强和增强图像上手动测量EAT衰减。使用半自动软件计算FAI。对于参考EID CT，模型脂肪插入物的衰减为-69 HU；对于PCD CT，在70 keV时观察到小模型（-69 HU）和大模型（-70 HU）的衰减最接近。在患者中，非增强采集时EAT衰减从55 keV时的-111±11 HU增加到80 keV时的-82±9 HU，增强采集时从55 keV时的-104±11 HU增加到80 keV时的-81±9 HU。非增强和增强扫描之间的平均衰减差异随着能量水平的增加而减小（从7±12 HU降至1±10 HU）。右冠状动脉的FAI从55 keV时的-89±8 HU增加到80 keV时的-77±12 HU，左前降支动脉从55 keV时的-95±11 HU增加到80 keV时的-85±11 HU，回旋动脉从55 keV时的-87±10 HU增加到80 keV时的-80±12 HU。使用PCD CT进行的EAT衰减和FAI测量受VMI能量水平和对比增强的影响。使用70 keV的VMI重建可提供接近传统多色测量的脂肪衰减。这些发现可能有助于标准化PCD CT对冠状动脉周围炎症的评估，作为衡量患者心脏风险的指标。
