70kV管电压在头颅CT血管成像中的可行性

Feasibility study of cerebral CT angiography using 70kVp tube voltage

目的:探讨70kV管电压在头颅CT血管成像中的可行性。方法:80例临床疑似脑血管疾病的患者随机分成2组,其中40例患者行新双源CT 70kV头颅CT血管成像(70kV组),另40例患者行120kV头颅CT血管成像(120kV组)。测量每例患者颈内动脉、大脑中动脉CT值,计算信噪比(SNR)和对比噪声比(CNR)。两名放射医师对所有病例以4分法对图像质量进行评分。计算有效剂量(ED)。比较两组间的图像质量及辐射剂量。结果:70kV组颈内动脉及大脑中动脉的平均CT值[(511.1±93.8)HU,(459.1±83.4)HU]高于120kV组的CT值[(289.1±46.6)HU,(260.9±43.4)HU,P<0.001]。70kV组图像噪声[(18.3±2.1)HU]高于120kV组[(8.7±1.0)HU,P<0.001],70kV组的SNR颈内动脉,CNR颈内动脉及SNR大脑中动脉,CNR大脑中动脉(28.3±6.1,26.2±5.9及25.4±5.3,23.3±5.2)低于120kV组(33.9±7.5,30.1±7.1及30.7±7.4,26.9±6.9,P<0.05)。70kV组的主观评分(3.5±0.7)与120kV组(3.6±0.5,P=0.22)无显著性差异;两组读者间一致性为中等(kappa值=0.54,0.59,P<0.001)。70kV组与120kV组ED分别为(0.2±0.0)、(1.2±0.1)mSv(P<0.001),辐射量降低了80%。结论:70kV管电压在头颅CT血管成像中是可行的,能在降低辐射量的同时保持足够的图像质量。

Objective：To explore the radiation dose and image quality of cerebral CT angiography using 70kVp tube voltage.Methods：Eighty patients with clinically suspected cerebrovascular disease were divided into two groups.One group （40 patients）underwent cerebral CT angiography with 70kVp tube voltage,while the other group （40 patients）underwent conventionaltube voltage （120kVp）cerebral CT angiography.The CT values of the internal carotid artery （ICA）and the middle cerebral artery （MCA）in each patient were measured.Signal-to-noise ratio （SNR）and contrast-to-noise ratio （CNR）in each patient were also calculated.Two observers blindly evaluated the image quality using a 4-point scale.Effective dose （ED）was calculated for each patient.Results：The 70kVp group showed higher CT values [（511.1±93.8）HU, （459.1±83.4）HU]than 120kVp group [（289.1±46.6）HU,（260.9±43.4）HU,P〈0.001）.Image noise of 70kVp group [（18.3±2.1）HU]was higher than 120kVp group [（8.7±1.0）HU,P〈0.001],the SNRICA,CNRICA and SNRMCA, CNRMCA （28.3±6.1,26.2±5.9 vs 25.4±5.3,23.3±5.2）of 70kV group were lower than 120kV group （33.9±7.5, 30.1±7.1 vs 30.7±7.4,26.9±6.9;P〈0.05）.There were no significant differences between the 70kVp group （3.5± 0.7）and the 120kVp group （3.6±0.5,P= 0.22）regarding the mean score.Moderate interreader agreement was found for both groups （kappa values were 0.54 and 0.59,all the P value〈0.001）.ED were （0.2±0.0）mSv and （1.2±0.1）mSv for 70kVp and 120kVp groups （P〈0.001）respectively,and the average effective dose was decreased by 80% in the 70kVp group.Conclusion：The application of 70kVp in cerebral CT angiography is feasible,it can reduce radiation dose without noticeable loss in diagnostic quality.