From the Division of Cardiovascular Imaging, Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston.
Department of Radiology, University Hospital, LMU Munich, Munich, Germany.
Invest Radiol. 2023 Sep 1;58(9):673-680. doi: 10.1097/RLI.0000000000000959.
The aim of this study was to evaluate the impact of virtual monoenergetic imaging (VMI) and quantum iterative reconstruction (QIR) on the accuracy of coronary artery calcium scoring (CACS) using a virtual noniodine (VNI) reconstruction algorithm on a first-generation, clinical, photon counting detector computed tomography system.
Coronary artery calcium scoring was evaluated in an anthropomorphic chest phantom simulating 3 different patient sizes by using 2 extension rings (small: 300 × 200 mm, medium: 350 × 250 mm, large: 400 × 300 mm) and in patients (n = 61; final analyses only in patients with coronary calcifications [n = 34; 65.4 ± 10.0 years; 73.5% male]), who underwent nonenhanced and contrast-enhanced, electrocardiogram-gated, cardiac computed tomography on a photon counting detector system. Phantom and patient data were reconstructed using a VNI reconstruction algorithm at different VMI (55-80 keV) and QIR (strength 1-4) levels (CACS VNI ). True noncontrast (TNC) scans at 70 keV and QIR "off" were used as reference for phantom and patient studies (CACS TNC ).
In vitro and in vivo CACS VNI showed strong correlation ( r > 0.9, P < 0.001 for all) and excellent agreement (intraclass correlation coefficient > 0.9 for all) with CACS TNC at all investigated VMI and QIR levels. Phantom and patient CACS VNI significantly increased with decreasing keV levels (in vitro: from 475.2 ± 26.3 at 80 keV up to 652.5 ± 42.2 at 55 keV; in vivo: from 142.5 [7.4/737.7] at 80 keV up to 248.1 [31.2/1144] at 55 keV; P < 0.001 for all), resulting in an overestimation of CACS VNI at 55 keV compared with CACS TNC at 70 keV in some cases (in vitro: 625.8 ± 24.4; in vivo: 225.4 [35.1/959.7]). In vitro CACS increased with rising QIR at low keV. In vivo scores were significantly higher at QIR 1 compared with QIR 4 only at 60 and 80 keV (60 keV: 220.3 [29.6-1060] vs 219.5 [23.7/1048]; 80 keV: 152.0 [12.0/735.6] vs 142.5 [7.4/737.7]; P < 0.001). CACS VNI was closest to CACS TNC at 60 keV, QIR 2 (+0.1%) in the small; 55 keV, QIR 1 (±0%) in the medium; 55 keV, QIR 4 (-0.1%) in the large phantom; and at 60 keV, QIR 1 (-2.3%) in patients.
Virtual monoenergetic imaging reconstructions have a significant impact on CACS VNI . The effects of different QIR levels are less consistent and seem to depend on several individual conditions, which should be further investigated.
本研究旨在评估使用第一代临床光子计数探测器 CT 系统的虚拟非碘（VNI）重建算法，在虚拟单能量成像（VMI）和量子迭代重建（QIR）对冠状动脉钙化评分（CACS）准确性的影响。
通过使用 2 个扩展环（小：300×200mm，中：350×250mm，大：400×300mm）和患者（n=61；仅对有冠状动脉钙化的患者进行最终分析[n=34；65.4±10.0 岁；73.5%为男性]）进行了人体胸部模拟体模的冠状动脉钙化评分评估，患者接受了非增强和对比增强、心电图门控、心脏 CT 检查。使用 VNI 重建算法在不同的 VMI（55-80keV）和 QIR（强度 1-4）水平（CACS VNI）下对体模和患者数据进行重建。真非对比（TNC）扫描在 70keV 和 QIR“关闭”时用作体模和患者研究的参考（CACS TNC）。
在体外和体内，CACS VNI 与 CACS TNC 具有很强的相关性（所有 r > 0.9，P < 0.001）和极好的一致性（所有 ICC > 0.9），在所有研究的 VMI 和 QIR 水平下均如此。体模和患者的 CACS VNI 随着 keV 水平的降低而显著增加（体外：从 80keV 时的 475.2±26.3 增加到 55keV 时的 652.5±42.2；体内：从 80keV 时的 142.5[7.4/737.7]增加到 55keV 时的 248.1[31.2/1144]；所有 P<0.001），导致 CACS VNI 在某些情况下在 55keV 时比 CACS TNC 在 70keV 时高估（体外：625.8±24.4；体内：225.4[35.1/959.7]）。在低 keV 时，体外 CACS 随 QIR 的升高而增加。仅在 60keV 和 80keV 时，体内 QIR 1 比 QIR 4 更高（60keV：220.3[29.6-1060] vs 219.5[23.7/1048]；80keV：152.0[12.0/735.6] vs 142.5[7.4/737.7]；P<0.001）。在小体模中，CACS VNI 在 60keV、QIR 2（+0.1%）时最接近 CACS TNC；在中体模中，在 55keV、QIR 1（±0%）时最接近；在大体模中，在 55keV、QIR 4（-0.1%）时最接近；在患者中，在 60keV、QIR 1（-2.3%）时最接近。
虚拟单能量成像重建对 CACS VNI 有显著影响。不同 QIR 水平的影响不太一致，似乎取决于几个个体条件，这需要进一步研究。
