Sakabe Daisuke, Nakaura Takeshi, Oda Seitaro, Kidoh Masafumi, Utsunomiya Daisuke, Masahiro Hatemura R T, Funama Yoshinori
Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
Diagnostic Radiology, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
BJR Open. 2020 Dec 11;2(1):20200006. doi: 10.1259/bjro.20200006. eCollection 2020.
To compare the estimated radiation dose of 50% reduced iodine contrast medium (halfCM) for virtual monochromatic images (VMIs) with that of standard CM (stdCM) with a 120 kVp imaging protocol for contrast-enhanced CT (CECT).
We enrolled 30 adults with renal dysfunction who underwent abdominal CT with halfCM for spectral CT. As controls, 30 matched patients without renal dysfunction using stdCM were also enrolled. CT images were reconstructed with the VMIs at 55 keV with halfCM and 120 kVp images with stdCM and halfCM. The Monte-Carlo simulation tool was used to simulate the radiation dose. The organ doses were normalized to CTDIvol for the liver, pancreas, spleen, and kidneys and measured between halfCM and stdCM protocols.
For the arterial phase, the mean organ doses normalized to CTDIvol for stdCM and halfCM were 1.22 and 1.29 for the liver, 1.50 and 1.35 for the spleen, 1.75 and 1.51 for the pancreas, and 1.89 and 1.53 for the kidneys. As compared with non-enhanced CT, the average increase in the organ dose was significantly lower for halfCM (13.8% ± 14.3 and 26.7% ± 16.7) than for stdCM (31.0% ± 14.3 and 38.5% ± 14.8) during the hepatic arterial and portal venous phases ( < 0.01).
As compared with stdCM with the 120 kVp imaging protocol, a 50% reduction in CM with VMIs with the 55 keV protocol allowed for a substantial reduction of the average organ dose of iodine CM while maintaining the iodine CT number for CECT.
This study provides that the halfCM protocol for abdominal CT with a dual-layer-dual-energy CT can significantly reduce the increase in the average organ dose for non-enhanced CT as compared with the standard CM protocol.
比较在120 kVp成像方案下，用于对比增强CT（CECT）的虚拟单色图像（VMI）的50%低碘对比剂（halfCM）与标准对比剂（stdCM）的估计辐射剂量。
我们纳入了30名肾功能不全的成年人，他们接受了使用halfCM的腹部光谱CT检查。作为对照，还纳入了30名匹配的使用stdCM的无肾功能不全患者。使用halfCM在55 keV下重建VMI的CT图像以及使用stdCM和halfCM重建120 kVp图像。使用蒙特卡罗模拟工具模拟辐射剂量。将肝脏、胰腺、脾脏和肾脏的器官剂量归一化为CTDIvol，并在halfCM和stdCM方案之间进行测量。
在动脉期，以CTDIvol归一化的stdCM和halfCM的平均器官剂量，肝脏分别为1.22和1.29，脾脏分别为1.50和1.35，胰腺分别为1.75和1.51，肾脏分别为1.89和1.53。与非增强CT相比,在肝动脉期和门静脉期，halfCM（13.8%±14.3和26.7%±16.7）的器官剂量平均增加幅度明显低于stdCM（31.0%±14.3和38.5%±14.8）（P<0.01）。
与120 kVp成像方案的stdCM相比，55 keV方案的VMI使用的对比剂减少50%，在保持CECT碘CT值的同时，可大幅降低碘对比剂的平均器官剂量。
本研究表明，与标准对比剂方案相比，双层双能量CT腹部CT的halfCM方案可显著降低非增强CT的平均器官剂量增加幅度。
