腰椎及椎间盘病变低剂量螺旋CT扫描技术改进初探

Original Research of Technological Improvement of Low Dose Spiral Computed Tomography in Lumbar Vertebra and Lumbar Intervertebral Disc Diseases

目的探讨自动管电流调节技术(ATCM)及其参数在腰椎螺旋CT容积扫描中降低辐射剂量的价值。资料与方法前瞻性连续搜集本院进行腰椎螺旋CT检查患者50例,随机分为5小组,记录受检者体重指数(BMI),分别接受以下5组不同参数组合CT扫描:第1组采用固定管电流技术,405 mAs,120 kV;第2～5组均采用智能毫安秒技术,噪声值(NI)分别为21 HU、25 HU、25 HU、25 HU,管电流范围分别为100～710 mAs、100～710mAs、40～300 mAs、40～300 mAs,管电压分别为120 kV、120 kV、120 kV、100 kV。进行以上参数扫描同时记录随机的容积CT剂量指数(CTDIvol)及剂量长度乘积(DLP)。对获得容积再现(VR)重组及batch重组图像进行图像质量评分(IQS),并测量各组参数下L3～4、L4～5、L5～S1椎间盘中心水平腰大肌的标准差(SD)值。对所获得数值进行统计学分析。结果不同参数组间BMI无统计学差异。各组CTDIvol值存在明显统计学差异(P﹤0.01),第4组、第5组CTDIvol值为第1组的56.63%、40.03%;各组DLP值存在明显统计学差异(P﹤0.01),第4组、第5组DLP值为第1组的55.29%、39.78%。各组VR及batch重组图像评分存在统计学差异。VR重组图像评分在第1～4组间无统计学差异,第5组图像评分与各组均存在统计学差异;batch图像评分中第1组、第2组均与第5组存在统计学差异。各组L3～4、L4～5、L5～S1椎间盘水平腰大肌的SD值存在统计学差异,第1～4组均与第5组存在统计学差异。结论正确使用自动管电流调节技术可以在确保图像质量的同时降低受检者所受辐射剂量,采用NI25 HU、管电流范围40～300 mAs、管电压120 kV可降低43.37%的辐射剂量。

Objective To explore the value of radiation dose reduction for lumbar vertebra volume CT examinations with automatic tube current modulation（ATCM） and its different parameters.Materials and Methods 50 patients who underwent lumbar multislice CT examination were prospectively collected,whose body mass index（BMI） were recorded.They were randomly divided into 5 groups,undergoing different scan parameters.Group 1 received CT scan with fixed tube current 405mAs and tube voltage 120 kV/Group 2,group 3,group 4,group 5 were examined with SmartmA,whose noise index（NI） was respectively 21 HU,25 HU,25 HU,25 HU,range of tube current was respectively 100-710 mAs,100-710 mAs,400-300 mAs,40-300 mAs,and tube voltage was respectively 120 kV,120 kV,120 kV,100 kV.The CT dose index of volume（CTDIvol） and the dose length product（DLP） were recorded.VR and batch reconstruction imaging were evaluated by the image quality score（IQS）.The image standard deviation（SD） of psoas major was measured at the middle level of L3-4,L4-5,L5-S1 lumbar disc in different groups.The statistical analysis was performed.Results There was not statistical difference in BMI between different groups.The CTDIvol of different groups existed significant statistical difference（P﹤0.01）.The CTDIvol of group 4,group 5 was 56.63%,40.03% of group 1.There was significant statistical difference in DLP among different groups（P﹤0.01）.The DLP of group 4,group 5 was respectively 55.29%、39.78% of group 1.IQS of VR and batch imaging showed statistical difference,and IQS of group 1-4 showed statistical difference with group 5.There was significant difference in IQS of batch imaging between group 1 and 5,group 2 and 5.There was statistical difference in SD index of psoas major muscle.SD index of group 1-4 showed statistical difference with group 5.Conclusion The correct application of ATCM could reduce the dose of examinee and ensure the quality of imaging.ATCM with NI equal to 25,range of tube current 40-300 mAs,tube voltage 120 kV could decrease 43.37% radiation dose.