Pitteloud Janique, Moser Lukas J, Klambauer Konstantin, Mergen Victor, Flohr Thomas, Eberhard Matthias, Alkadhi Hatem
Department of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Raemistrasse 100, Zurich 8091, Switzerland.
AJR Am J Roentgenol. 2024 Nov;223(5):e2431607. doi: 10.2214/AJR.24.31607. Epub 2024 Aug 21.
Pericoronary adipose tissue (PCAT) attenuation and the fat attenuation index (FAI) may serve as markers of inflammation and the risk of adverse cardiac events. However, standardization of relevant CT acquisition and reconstruction parameters is lacking. The purpose of this study was to investigate the influence of vessel attenuation, the virtual monoenergetic image (VMI) level, and the reconstruction kernel on PCAT attenuation and FAI by use of energy-integrating detector (EID) and photon-counting detector (PCD) CT systems in an ex vivo porcine heart model. The right coronary artery (RCA) of a porcine heart was injected with saline or varying contrast medium dilutions to achieve vessel attenuation ranging from 0 to 1000 HU. After each injection, the heart was sequentially scanned by EID CT at 120 kVp and PCD CT at 140 kVp at a constant CTDI of 10 mGy. For EID CT, polychromatic images were reconstructed with a Qr40 kernel. For PCD CT, VMIs (obtained at 40-80 keV in 10-keV increments) were reconstructed with Qr40, Bv40, and Bv56 kernels. ROIs were placed to measure RCA and PCAT attenuation. FAI was determined using software; histogram analysis was performed to assess voxel attenuation in the volumes of interest for FAI calculation. Correlations were observed between attenuation in the RCA and attenuation in the adjacent PCAT ( = 0.3-1.0) and between vessel attenuation and the FAI ( = -0.9 to 1.0). For PCAT attenuation and the FAI, these associations became progressively weaker when progressively sharper kernels were used. For increasing vessel attenuation on EID CT and for increasing VMI level on PCD CT, FAI histograms showed right shifts in peak attenuation values; the percentage of histogram voxels that met the threshold range for inclusion in FAI calculation was 9-38% for EID CT and 6-39% for PCD CT at VMI levels of 70-80 keV. For PCD CT, use of sharper kernels was associated with left shifts in peak attenuation values and greater percentages of voxels within the threshold range for inclusion in FAI calculation. PCAT attenuation and the FAI are influenced by vessel lumen attenuation, the VMI level, and the reconstruction kernel. A minority of pericoronary voxels contribute to FAI measurements for polychromatic EID CT and for PCD CT at high VMI levels. These findings may help standardize acquisition and reconstruction parameters for PCAT attenuation and FAI measurements.
冠状动脉周围脂肪组织（PCAT）衰减和脂肪衰减指数（FAI）可作为炎症和不良心脏事件风险的标志物。然而，相关CT采集和重建参数缺乏标准化。本研究的目的是在离体猪心脏模型中，利用能量积分探测器（EID）和光子计数探测器（PCD）CT系统，研究血管衰减、虚拟单能图像（VMI）水平和重建核函数对PCAT衰减和FAI的影响。向猪心脏的右冠状动脉（RCA）注射生理盐水或不同浓度的对比剂稀释液，以使血管衰减范围为0至1000 HU。每次注射后，以10 mGy的恒定CTDI，先通过EID CT在120 kVp下对心脏进行扫描，然后通过PCD CT在140 kVp下进行扫描。对于EID CT，用Qr40核函数重建多色图像。对于PCD CT，用Qr40、Bv40和Bv56核函数重建VMI（以10 keV增量在40 - 80 keV获得）。放置感兴趣区（ROI）以测量RCA和PCAT衰减。使用软件确定FAI；进行直方图分析以评估用于FAI计算的感兴趣体积内的体素衰减。观察到RCA衰减与相邻PCAT衰减之间存在相关性（= 0.3 - 1.0），以及血管衰减与FAI之间存在相关性（= -0.9至1.0）。对于PCAT衰减和FAI，当使用逐渐锐利的核函数时，这些关联逐渐减弱。对于EID CT上血管衰减增加以及PCD CT上VMI水平增加，FAI直方图显示峰值衰减值向右偏移；在70 - 80 keV VMI水平下，EID CT的直方图体素中符合FAI计算纳入阈值范围的百分比为9 - 38%，PCD CT为6 - 39%。对于PCD CT，使用更锐利的核函数与峰值衰减值向左偏移以及FAI计算纳入阈值范围内的体素百分比增加相关。PCAT衰减和FAI受血管腔衰减、VMI水平和重建核函数的影响。对于多色EID CT和高VMI水平的PCD CT，少数冠状动脉周围体素对FAI测量有贡献。这些发现可能有助于标准化PCAT衰减和FAI测量的采集和重建参数。
