基于单光子计数的头颈部血管 CT 成像：初步人体研究结果
Photon-Counting Computed Tomography for Vascular Imaging of the Head and Neck: First In Vivo Human Results.
出版信息
Invest Radiol. 2018 Mar;53(3):135-142. doi: 10.1097/RLI.0000000000000418.
PURPOSE
The purpose of this study was to evaluate image quality of a spectral photon-counting detector (PCD) computed tomography (CT) system for evaluation of major arteries of the head and neck compared with conventional single-energy CT scans using energy-integrating detectors (EIDs).
METHODS
In this institutional review board-approved study, 16 asymptomatic subjects (7 men) provided informed consent and received both PCD and EID contrast-enhanced CT scans of the head and neck (mean age, 58 years; range, 46-75 years). Tube settings were (EID: 120 kVp/160 mA vs PCD: 140 kVp/108 mA) for all volunteers. Quantitative analysis included measurements of mean attenuation, image noise, and contrast-to-noise ratio (CNR). Spectral PCD data were used to reconstruct virtual monoenergetic images and iodine maps. A head phantom was used to validate iodine concentration measurements in PCD images only. Two radiologists blinded to detector type independently scored the image quality of different segments of the arteries, as well as diagnostic acceptability, image noise, and severity of artifacts of the PCD and EID images. Reproducibility was assessed with intraclass correlation coefficient. Linear mixed models that account for within-subject correlation of analyzed arterial segments were used. Linear regression and Bland-Altman analysis with 95% limits of agreement were used to calculate the accuracy of material decomposition.
RESULTS
Photon-counting detector image quality scores were significantly higher compared with EID image quality scores with lower image noise (P < 0.01) and less image artifacts (P < 0.001). Photon-counting detector image noise was 9.1% lower than EID image noise (8.0 ± 1.3 HU vs 8.8 ± 1.5 HU, respectively, P < 0.001). Arterial segments showed artifacts on EID images due to beam hardening that were not present on PCD images. On PCD images of the head phantom, there was excellent correlation (R = 0.998) between actual and calculated iodine concentrations without significant bias (bias: -0.4 mg/mL [95% limits of agreements: -1.1 to 0.4 mg/mL]). Iodine maps had 20.7% higher CNR compared with nonspectral PCD (65.2 ± 9.0 vs 54.0 ± 4.5, P = 0.01), and virtual monoenergetic image at 70 keV showed similar CNR to nonspectral images (52.6 ± 4.2 vs 54.0 ± 4.5, P = 0.39).
CONCLUSIONS
Photon-counting CT has the potential to improve the image quality of carotid and intracranial CT angiography compared with single-energy EID CT.
目的
本研究旨在评估与使用能量积分探测器（EID）的常规单能量 CT 扫描相比，头部和颈部主要动脉的光谱光子计数探测器（PCD） CT 系统的图像质量。
方法
在这项经机构审查委员会批准的研究中，16 名无症状受试者（7 名男性）提供了知情同意，并接受了头部和颈部的 PCD 和 EID 对比增强 CT 扫描（平均年龄 58 岁；范围，46-75 岁）。所有志愿者的管电压设置均为（EID：120 kVp/160 mA 与 PCD：140 kVp/108 mA）。定量分析包括测量平均衰减、图像噪声和对比噪声比（CNR）。光谱 PCD 数据用于重建虚拟单能量图像和碘图。头部体模仅用于验证 PCD 图像中碘浓度的测量。两名对探测器类型不知情的放射科医生独立对不同动脉段的图像质量以及图像噪声和 PCD 和 EID 图像伪影的严重程度进行评分。使用组内相关系数评估可重复性。使用线性混合模型，该模型考虑了分析的动脉段的个体内相关性。使用线性回归和 Bland-Altman 分析（95%一致性界限）来计算物质分解的准确性。
结果
与 EID 图像质量评分相比，PCD 图像质量评分明显更高，图像噪声更低（P < 0.01），图像伪影更少（P < 0.001）。PCD 图像噪声比 EID 图像噪声低 9.1%（分别为 8.0 ± 1.3 HU 和 8.8 ± 1.5 HU，P < 0.001）。EID 图像上的动脉段由于束硬化而出现伪影，而 PCD 图像上则没有。在头部体模的 PCD 图像上，实际和计算的碘浓度之间存在极好的相关性（R = 0.998），且没有显著偏差（偏差：-0.4 mg/mL [95%一致性界限：-1.1 至 0.4 mg/mL]）。碘图的 CNR 比非光谱 PCD 高 20.7%（65.2 ± 9.0 与 54.0 ± 4.5，P = 0.01），70 keV 的虚拟单能量图像与非光谱图像的 CNR 相似（52.6 ± 4.2 与 54.0 ± 4.5，P = 0.39）。
结论
与单能量 EID CT 相比，光子计数 CT 有可能改善颈动脉和颅内 CT 血管造影的图像质量。
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