体质量指数指导Z轴自动管电流调制技术在胸部CT扫描中应用价值

目的评价体质量指数（BMI）指导下降低Z轴自动管电流调制技术最大毫安值在胸部CT扫描中的图像质量和辐射剂量,降低辐射剂量应用价值。方法连续选取100例BMI正常同时胸部CT定位像扫描显示无明显异常的受检者,随机分2组,每组50例。低剂量组,男性30例,女性20例,年龄18～75岁,中位年龄为39.74岁;对照组,男性30例,女性20例,年龄18～75岁,中位年龄为41.8岁。2组均使用Z轴自动管电流调制技术,Z轴自动管电流设置范围低剂量组30～200mA,对照组30～350mA。记录CT扫描后机显示容积CT剂量指数（CTDIvol）和剂量长度乘积（DLP）,计算有效剂量（ED）。取每例患者肺尖部、主动弓部、肺底部3幅图像,共计300幅。由2名副主任医师采用5分制双盲法评判,测量相应部位的噪声。所有数据记录录入Excel,分析采用SPSS13.0。结果低剂量组和对照组的图像质量主观评判均符合临床诊断要求。低剂量组的图像噪声肺尖部为12.27±2.64,主动弓部为10.83±2.03,肺底部为13.67±2.98。对照组图像噪声肺尖部10.96±2.42,主动脉弓部为9.71±2.72,肺底部为11.17±2.06。低剂量组噪声值高于对照组,两组比较,差异有统计学意义（P〈0.05）。低剂量组平均CTDIvol、ED分别为（5.89±1.63）mGy、（3.26±0.92）mSv,对照组平均CTDIvol、ED分别为（8.07±2.13）mGy、（4.47±1.20）mSv。结论BMI指导下降低Z轴自动管电流调制技术最大毫安值在胸部CT扫描中既能保证图像满足诊断要求,又大幅降低了受检者辐射剂量。

Application value of Z-axis tube-current modulation technique guided by body mass index in CT chest scanning

Objective To evaluate the image quality and radiation doses for decreasing the maximum milliampere（mA） value of Z- axis tube-current modulation technique guided by body mass index（BMI） in CT chest scanning. Methods A total of 100 cases with normal BMI and normal CT scan image were enrolled, which randomly divided into 2 groups, male 30, female 20, aged 18 - 75 years old, median age 39.74 years old in low-dose group, and male 30, female 20, aged 18 - 75 years old, median age 41.8 years old in control group. The Z-axis tube-current modulation techniques were used in two groups, the range of low-dose group was 30 - 200 mA, and control group was 30 - 350 mA. The volume CT dose index（CTDIvol） and dose length product（DLP） displayed in CT were recorded and effect dose（ED） was calculated. The noise lever of image at upper lung, aorta arches and bottom lung level were measured and compared. The image quality was classified in five levels with double blind method. All data were recorded in Excel, and analyzed using SPSS 13.0. Results The image qualities of control group and low-dose group were conformed clinical diagnostic requirements. The noise level of image at upper lung, aorta arch and bottom lung in control group and low-dose group were 12.27 ± 2.64, 10.83 ±2.03, 13.67± 2.98 and 10.96 ± 2.42, 9.71 ±2.72, 11.17 ±2.06, respectively. CTDIvol and ED of control group and low- dose group were （5.89 ±1.63） mGy, （3.26 ±0.92） mSv and （8.07 ±2.13） mGy, （4.47 ±1.20） mSv, respectively. The noise lever of control group was higher than those of low-dose group, and CTDIvol and ED of control group were significantly decreased than those of low- dose group. Conclusion It is demonstrated that radiation doses of decreasing the maximum mA value of Z-axis tube-current modulation technique guided by BMI in CT chest scanning are not only assure the image qualities to fit for clinical diagnostic requirements, but also decrease the radiation dose.