Institute of Diagnostic and Interventional Radiology, University Hospital of Cologne, Cologne, Germany.
Philips Healthcare, Best, The Netherlands.
Eur J Radiol. 2018 Feb;99:28-33. doi: 10.1016/j.ejrad.2017.12.007. Epub 2017 Dec 11.
To investigate the utilization of virtual mono-energetic images (MonoE) at low kiloelectron volt (keV) levels derived from a dual-layer spectral detector CT (SDCT) for the assessment of abdominal arteries in venous contrast phase scans using arterial phase imaging as an internal reference standard.
A total of 50 patients who received arterial and venous phase imaging of the abdomen on a SDCT system were included in this study. Absolute attenuation, noise, signal- and contrast to noise ratios (SNR; CNR) as well as arterial diameters in defined landmarks were assessed. In arterial phase, conventional reconstructions (CR) as well as MonoE at 40keV and in venous phase, conventional reconstructions (CR) as well as MonoE at 70 and 40keV were investigated and intra-individual comparisons were performed. If an artery stenosis (10 patients) was present, the degree of stenosis was assessed according to the system of the North American Symptomatic Carotid Endarterectomy Trial (NASCET).
MonoE 40keV yielded significantly higher attenuation values (in arterial as well as in venous phase) compared to CR (p<0.001) while noise levels were substantially low. This resulted in markedly superior SNR and CNR in large vessel compared to CR. Luminal diameters were significantly smaller in MonoE 40keV in both contrast phases compared to CR (p<0.001), whereas no significant differences were found between both MonoE reconstructions (p≥0.92). The degree of vessel stenosis was significantly higher in MonoE 40keV of both contrast phases compared to CR (p≥0.02).
MonoE at low keV of venous contrast phase scans derived from a novel SDCT are suitable for the assessment of arteries in the abdomen and subsequent stenosis assessment. However, MonoE at 40keV constantly showed significant smaller luminal diameters than the corresponding conventional reconstructions (including the reference standard). This is possibly due to an improved differentiation of the vessel lumen from the wall and raises the question, which imaging technique should be used as an appropriate reference standard for vascular SDCT imaging studies.
利用双层光谱探测器 CT（SDCT）衍生的虚拟单能量图像（MonoE）在低千伏（keV）水平下评估静脉对比期扫描的腹部动脉，以动脉期成像作为内部参考标准。
本研究共纳入 50 例在 SDCT 系统上进行腹部动脉期和静脉期成像的患者。评估绝对衰减、噪声、信噪比（SNR）和对比噪声比（CNR）以及定义标志处的动脉直径。在动脉期，研究了常规重建（CR）以及 40keV 的 MonoE，在静脉期，研究了常规重建（CR）以及 70keV 和 40keV 的 MonoE，并进行了个体内比较。如果存在动脉狭窄（10 例），则根据北美症状性颈动脉内膜切除术试验（NASCET）系统评估狭窄程度。
与 CR 相比，MonoE 40keV 在动脉期和静脉期均产生了显著更高的衰减值（p<0.001），而噪声水平则显著降低。这导致在大血管中 SNR 和 CNR 明显优于 CR。与 CR 相比，MonoE 40keV 在两个对比期的管腔直径均显著较小（p<0.001），而两种 MonoE 重建之间无显著差异（p≥0.92）。与 CR 相比，MonoE 40keV 在两个对比期的血管狭窄程度均显著更高（p≥0.02）。
源自新型 SDCT 的静脉对比期扫描的低 keV MonoE 适用于腹部动脉的评估和随后的狭窄评估。然而，MonoE 40keV 的管腔直径始终明显小于相应的常规重建（包括参考标准）。这可能是由于血管内腔与壁之间的区分得到了改善，并提出了一个问题，即哪种成像技术应作为血管 SDCT 成像研究的适当参考标准。
