64层CT盆腔动脉成像质量及辐射剂量的研究

目的初步探讨64层CT盆腔动脉成像中低mAs技术应用价值，评价其图像质量和辐射剂量。方法选取50例日常盆腔增强检查患者随机分为A、B2组，A组24例使用250mAs进行CT盆腔动脉成像，B组26例使用100mAs。通过cT机自动得到CT剂量指数（CT dose index，CTDI）和剂量长度乘积（dose length product，DLP）。对2组扫描数据分别进行多种图像后处理，2名有经验的影像科医师采用双盲法评价图像质量，测量噪声及CT值。两组图像ROI的CT值、噪声、SNR、辐射剂量及图像质量评分用两独立样本t检验进行统计分析。2名医师评分一致性采用Kappa检验。结果A组盆腔动脉分支图像质量评分为2．9±O．1，B组为2．8±0．1，2组之间比较差异无统计学意义（P〉0．05）。A组CTDI、DLP和ED分别为14．7、458．5±13．3和8．7±0．3，而B组分别为6．4、179．9±8．9和3。4±0．2，2组CTDI、DLP和ED之间比较差异有统计学意义（P〈O．05）。2组问髂内动脉平均SNR差异有统计学意义。A组评价144分支，B组评价156分支，A、B组优良者分别达到100％和98．1％。结论低mAs盆腔动脉扫描可在保证图像质量的同时显著降低辐射剂量。

Optimized imaging quality and radiation dose for pelvic angiography using 64-slice CT

Objective To evaluate the image quality and the radiation dose in 64-slice CT pelvic angiography by using low mAs mode. Methods Fifty patients who underwent pelvic angiography on a 64-slice CT scanner were randomized two groups （group A and group B）. Twenty-four patients in group A were examined with 250 mAs, and twenty-six patients in group B with 150 mAs. The CTDI value and DLP value were automatically recorded by CT scanner. All images were transferred to a workstation for further processing and analysis. Two observers blinded to clinical data independently as- sessed the image quality, and measured the image noise, signal-to-noise ratio （SNR） and CT values. The CT value, ima- ging noise, SNR, radiation dose and imaging quality scores were compared between the two groups with t test. The inter- obverser agreement was determined by Kappa statistics. Results The mean score of imaging quality for pelvic artery bran- ches in group A was 2.9 ± 0.1 and that in group B was 2.8 ~ 0.1, there was no statistical difference in imaging quality be- tween the two groups （ P 〉0.05）. The CTDI, DLP and ED were 14.7, 458.5±13.3 and 8.7±0.3 respectively in the group A, whereas, 6.4, 179.9±8.9 and 3.4±0.2 in group B, there was a statistical difference between the two groups. The mean SNR of the internal iliac artery was 15. 1± 0.7 in group A and 12.3 ± 1.3 in group B, there was statistical difference in SNR of the internal iliac artery between the two groups. A total of 144 pelvic artery branches were evaluated in group A and 156 branches were evaluated in group B, excellent or good was achieved in 100% and 98.1% in A and B group, respectively. Conclusion The low mAs pelvic angiography scanning can substantially reduce radiation while pre- serving good imaging quality.