Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
AJR Am J Roentgenol. 2011 Jun;196(6):1324-31. doi: 10.2214/AJR.10.4545.
The purpose of this study was to compare the diagnostic capability of hepatic dynamic CT with low-dose contrast material (420 mg I/kg body weight) at 80 kVp with that of the same modality performed with standard-dose contrast material at 120 kVp.
We randomly assigned 111 patients (50 women, 61 men; mean age, 69.1 years) with known or suspected hepatocellular carcinoma and a body weight of 70 kg or less to one of two protocols. In the 80-kVp protocol, the contrast material (444 mg I/kg body weight) was delivered over 15 seconds at a tube voltage of 80 kVp. In the 120-kVp protocol, a contrast dose of 600 mg I/kg was delivered over 30 seconds at 120 kVp. Of the 111 patients, 38 had hypervascular hepatocellular carcinoma. Using the Mann-Whitney U test, we compared the two protocols for the contrast-to-noise ratio of the tumors (difference between tumor attenuation and liver attenuation divided by noise in the liver) and the figure of merit (square of contrast-to-noise ratio divided by effective dose) of the tumors during the arterial phase of imaging. Effective doses also were compared.
The contrast-to-noise ratio of the tumors was significantly higher with the 80-kVp than with the 120-kVp protocol (median, 5.3 vs 4.2; p = 0.04). The figure of merit also was significantly higher with the 80-kVp than with the 120-kVp protocol (10.2 vs 5.3, p = 0.02). The effective dose was significantly lower with the 80-kVp than with the 120-kVp protocol (2.97 vs 3.41 mSv, p < 0.01).
With 80-kVp acquisition, the contrast-to-noise ratio and figure of merit of tumors during the arterial phase improved despite the lower contrast dose and radiation exposure.
本研究旨在比较低剂量对比剂（420mgI/kg 体重）在 80kVp 下与相同条件下标准剂量对比剂（120kVp）行肝脏动态 CT 的诊断能力。
我们将 111 例体重 70kg 或以下的已知或疑似肝细胞癌患者（50 例女性，61 例男性；平均年龄 69.1 岁）随机分为两组。在 80kVp 组中，以 80kVp 管电压在 15 秒内输送 444mgI/kg 对比剂。在 120kVp 组中，以 120kVp 管电压在 30 秒内输送 600mgI/kg 对比剂。111 例患者中，38 例为富血管性肝细胞癌。采用 Mann-Whitney U 检验，比较了两种方案在肿瘤动脉期的肿瘤对比噪声比（肿瘤衰减与肝衰减差值与肝内噪声比值）和肿瘤优劣比（对比噪声比的平方与有效剂量比值），并比较了有效剂量。
与 120kVp 方案相比，80kVp 方案的肿瘤对比噪声比显著更高（中位数 5.3 比 4.2；p=0.04）。80kVp 方案的优劣比也显著高于 120kVp 方案（10.2 比 5.3，p=0.02）。80kVp 方案的有效剂量显著低于 120kVp 方案（2.97 比 3.41mSv，p<0.01）。
尽管 80kVp 组的对比剂剂量和辐射暴露较低，但动脉期肿瘤的对比噪声比和优劣比仍有改善。
