Department of Radiology, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo, 116-8567, Japan.
Department of Radiology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
Eur Radiol. 2019 Mar;29(3):1400-1407. doi: 10.1007/s00330-018-5724-4. Epub 2018 Sep 12.
To compare image quality of abdominal arteries between full-iodine-dose conventional CT and half-iodine-dose virtual monochromatic imaging (VMI).
We retrospectively evaluated images of 21 patients (10 men, 11 women; mean age, 73.9 years) who underwent both full-iodine (600 mg/kg) conventional CT and half-iodine (300 mg/kg) VMI. For each patient, we measured and compared CT attenuation and the contrast-to-noise ratio (CNR) of the aorta, celiac artery, and superior mesenteric artery (SMA). We also compared CT dose index (CTDI). Two board-certified diagnostic radiologists evaluated visualisation of the main trunks and branches of the celiac artery and SMA in maximum-intensity-projection images. We evaluated spatial resolution of the two scans using an acrylic phantom.
The two scans demonstrated no significant difference in CT attenuation of the aorta, celiac artery, and SMA, but CNRs of the aorta and celiac artery were significantly higher in VMI (p = 0.011 and 0.030, respectively). CTDI was significantly higher in VMI (p = 0.024). There was no significant difference in visualisation of the main trunk of the celiac artery and SMA, but visualisation of the gastroduodenal artery, pancreatic arcade, branch of the SMA, marginal arteries, and vasa recta was significantly better in the conventional scan (p < 0.001). The calculated modular transfer function (MTF) suggested decreased spatial resolution of the half-iodine VMI.
Large-vessel depiction and CNRs were comparable between full-iodine conventional CT and half-iodine VMI images, but VMI did not permit clear visualisation of small arteries and required a larger radiation dose.
・Reducing the dose of iodine contrast medium is essential for chronic kidney disease patients to prevent contrast-induced nephropathy. ・In virtual monochromatic images at low keV, contrast of relatively large vessels is maintained even with reduced iodine load, but visibility of small vessels is impaired with decreased spatial resolution. ・We should be aware about the advantages and disadvantages associated with virtual monochromatic imaging with reduced iodine dose.
比较全碘剂量常规 CT 与半碘剂量虚拟单色成像（VMI）在腹部动脉成像中的图像质量。
我们回顾性分析了 21 例患者（男 10 例，女 11 例；平均年龄 73.9 岁）的全碘（600mg/kg）常规 CT 和半碘（300mg/kg）VMI 图像。对每位患者，我们分别测量并比较了主动脉、腹腔动脉和肠系膜上动脉的 CT 衰减值和对比噪声比（CNR）。还比较了 CT 剂量指数（CTDI）。两位具有认证资质的放射科医生对最大密度投影图像中腹腔动脉和肠系膜上动脉主干及其分支的显示情况进行了评估。使用亚克力体模评估了两次扫描的空间分辨率。
主动脉、腹腔动脉和肠系膜上动脉的 CT 衰减值在两种扫描方式中无显著差异，但 VMI 的主动脉和腹腔动脉 CNR 更高（分别为 p=0.011 和 0.030）。VMI 的 CTDI 显著更高（p=0.024）。腹腔动脉和肠系膜上动脉主干的显示情况无显著差异，但胃十二指肠动脉、胰腺弓、肠系膜上动脉分支、边缘动脉和直小血管的显示在常规扫描中更好（均 p<0.001）。计算的调制传递函数（MTF）提示半碘 VMI 的空间分辨率降低。
全碘常规 CT 与半碘 VMI 图像的大血管显示和 CNR 相当，但 VMI 无法清晰显示小动脉且需要更大的辐射剂量。
减少碘造影剂剂量对于预防对比剂肾病的慢性肾病患者至关重要。
在低 keV 的虚拟单色图像中，即使减少碘负荷，相对较大的血管的对比度也得以维持，但小血管的可视性因空间分辨率降低而受损。
我们应该了解与减少碘剂量的虚拟单色成像相关的优缺点。
