Juntunen Mikael A K, Kotiaho Antti O, Nieminen Miika T, Inkinen Satu I
University of Oulu, Research Unit of Medical Imaging, Physics, and Technology, Oulu, Finland.
Oulu University Hospital, Department of Diagnostic Radiology, Oulu, Finland.
J Med Imaging (Bellingham). 2021 Sep;8(5):052102. doi: 10.1117/1.JMI.8.5.052102. Epub 2021 Mar 10.
Coronary artery calcium (CAC) scoring with computed tomography (CT) has been proposed as a screening tool for coronary artery disease, but concerns remain regarding the radiation dose of CT CAC scoring. Photon counting detectors and iterative reconstruction (IR) are promising approaches for patient dose reduction, yet the preservation of CAC scores with IR has been questioned. The purpose of this study was to investigate the applicability of IR for quantification of CAC using a photon counting flat-detector. We imaged a cardiac rod phantom with calcium hydroxyapatite (CaHA) inserts with different noise levels using an experimental photon counting flat-detector CT setup to simulate the clinical CAC scoring protocol. We applied filtered back projection (FBP) and two IR algorithms with different regularization strengths. We compared the air kerma values, image quality parameters [noise magnitude, noise power spectrum, modulation transfer function (MTF), and contrast-to-noise ratio], and CaHA quantification accuracy between FBP and IR. IR regularization strength influenced CAC scores significantly ( ). The CAC volumes and scores between FBP and IRs were the most similar when the IR regularization strength was chosen to match the MTF of the FBP reconstruction. When the regularization strength is selected to produce comparable spatial resolution with FBP, IR can yield comparable CAC scores and volumes with FBP. Nonetheless, at the lowest radiation dose setting, FBP produced more accurate CAC volumes and scores compared to IR, and no improved CAC scoring accuracy at low dose was demonstrated with the utilized IR methods.
计算机断层扫描（CT）冠状动脉钙化（CAC）评分已被提议作为冠状动脉疾病的筛查工具，但对于CT CAC评分的辐射剂量仍存在担忧。光子计数探测器和迭代重建（IR）是降低患者剂量的有前景的方法，然而IR对CAC评分的保留受到了质疑。本研究的目的是使用光子计数平板探测器研究IR在CAC定量中的适用性。我们使用实验性光子计数平板探测器CT设置对带有不同噪声水平的羟基磷灰石（CaHA）插入物的心脏棒状模体进行成像，以模拟临床CAC评分方案。我们应用了滤波反投影（FBP）和两种具有不同正则化强度的IR算法。我们比较了FBP和IR之间的空气比释动能值、图像质量参数[噪声幅度、噪声功率谱、调制传递函数（MTF）和对比度噪声比]以及CaHA定量准确性。IR正则化强度对CAC评分有显著影响（ ）。当选择IR正则化强度以匹配FBP重建的MTF时，FBP和IR之间的CAC体积和评分最为相似。当选择正则化强度以产生与FBP相当的空间分辨率时，IR可以产生与FBP相当的CAC评分和体积。尽管如此，在最低辐射剂量设置下，与IR相比，FBP产生的CAC体积和评分更准确，并且所使用的IR方法在低剂量下未显示出改善的CAC评分准确性。
