Z轴自动管电流调制技术在头颈部CT扫描血管成像中对甲状腺剂量的降低

Reduction in thyroid dose from neck CT angiography with 64-slice spiral CT with automatic tube current modulation technique

目的 评价在进行头颈部CT扫描血管成像时,Z轴自动管电流调制技术（ATCM）对减少甲状腺的辐射剂量的作用及对图像噪声的影响.方法 回顾性地分析140例头颈部CT增强血管成像的病例,其中用固定管电流技术和Z轴自动管电流调节技术各70例,观察其成像质量,记录其客观噪声水平（由CT图像衰减值的标准差进行评估）,并比较其单次扫描的加权CT剂量指数CTDIw,管电流mA及剂量长度乘积DLP.结果 在扫描范围、扫描参数（管电压、螺距、准直器厚度等）、造影剂注射速率和注射部位完全相同的情况下,固定管电流技术和Z轴自动管电流调节技术的图像质量相同,甲状腺图像噪声分别为10.14和13.64 HU.单次扫描的加权CT剂量指数CTDIw（mGy）分别为（43.22±1.42）和（35.99±1.31）mGy.剂量长度乘积分别为（1514.45±5.56）和（1121.39±5.51）mGy·cm,剂量长度乘积降低约25.95%.结论 Z轴自动管电流调节技术能有效降低总曝光量和累计剂量长度乘积,可以有效地降低患者的辐射剂量,特别是像甲状腺和眼晶体等射线敏感组织器官的辐射剂量降低,减少其辐射危害,但是图像噪声略有增加.

Objective To assess the effectiveness of Z-axis automatic tube current modulation （ ATCM） technique with respect to dose reduction and image noise in the thyroid regional tissues during neck computed tomography angiography （CTA）. Methods A total of 140 patients underwent neck CTA with 64-slice spiral CT, and were randomized into fixed-tube current group and ATCM group. Objective noise, CTDIw, DLP and mA of each group were recorded. Results The image qualities of all the patients were diagnostically acceptable, though the objective noise of neck in the ATCM group was higher than that in the group of fixed-tube current （P＜ 0.05 ）. The radiation doses in the ATCM group [ CTDIw （35.99±1.31 ） mGy, DLP （11 121.39 ±5.51） mGy·cm] were significantly inferior to those in the group of fixed tube current [ CTDIw （43.22±1.42） mGy, DLP （1514.45±5.56） mGy·cm]. Conclusions Compared with fixedtube current technique, ATCM technique could significantly reduce the radiation dose in neck CT with diagnostic acceptability of the image quality.