基于迭代重组的双源CT腰椎低剂量扫描可行性研究

The Application of Low-Dose Scan in Lumbar Vertebrae Based on Iterative Image Reconstruction of Dual-Source CT

目的对比双源CT腰椎低剂量扫描基于原始数据的迭代重组（SAFIRE）和常规剂量扫描滤波反投影重组（FBP）的辐射剂量、图像质量,探讨腰椎CT低剂量扫描的可行性。方法将120例拟行腰椎CT扫描患者随机分为A、B、C三组,A组为常规剂量组,采用FBP重组;B组为低管电流组,C组为低管电压组,B、C组预计降低50%辐射剂量且均采用SAFIRE重组。记录并计算每例患者辐射剂量指标[CT剂量指数（CTDIvol）、剂量长度乘积（DLP）、有效辐射剂量（ED）],对比L4~5水平各组图像各感兴趣区（ROI）客观评价指标：信噪比（SNR）、椎间盘与硬膜囊对比噪声比（CNR）和主观评分,行统计学分析。结果 B组辐射剂量较A组平均降低约62%且各感兴趣区SNR及CNR与A组无显著统计学差异（P〉0.05）;C组辐射剂量较A组平均降低约70%,除L5骨松质之外,余ROI客观图像质量均低于A组（P〈0.05）;除椎小关节,A、B组图像主观评分无显著性差异;观察者间一致性很好。结论与常规剂量FBP相比,基于SAFIRE的腰椎CT低剂量扫描（管电流降低至常规50%）结合自动管电流调节技术（Care Dose）在明显降低辐射剂量的同时不影响图像质量,推荐将其作为腰椎疾病筛查方法。

Objective To compare radiation dose and image quality of the lumbar vertebrae produced by low-dose dualsource CT scan,Sinogram Affirmed iterative reconstruction（SAFIRE） with conventional dose scan,filter back-projection（FBP） reconstruction,to study the feasibility of low dose scanning of lumbar CT.Methods 120 patients underwent lumbar CT scan were randomly divided into A,B,C groups,group A is the conventional dose group,using FBP reconstruction; group B is the lower tube current group,group C is the lower tube voltage group,B and C groups were treated with SAFIRE reconstruction which intended end radiation dose was 50% less than the group A.Recorded and calculated radiation dose indicator for each case（CTDILOV,DLP,ED）,compare the objective evaluation indexes：the signal-to-noise ratio（SNR）,the contrast-to-noise ratio between intervertebral disc and the dural sac（D-D CNR） and the subjective scores of different reconstruction image of the every interest（ROI） at L4 /5level,then process statistical analysis.Results The average radiation dose of group B decreased 62% than group A,the SNR of every ROI and DNR had no significant difference compared with group A（P〈0.05）.Compared with group A,the average radiation dose of group C reduced about 70%,in addition to L5 vertebrae body,all ROI objective image quality is lower than that of group A（P〈0.05）; in addition to the vertebral small joint,A and B groups has no significant difference in subjective image score; All radiologists agreement performed very well.Conclusion Compared with conventional dose with FBP,Lumbar CT low dose scanning based on SAFIRE（the tube current reducing 50% compared with conventional） combined with automatic tube current modulation technique can significantly reduce the radiation dose,but not affect image quality,so it is recommended as a screening program for lumbar vertebral disease.