迭代重建技术在儿童胸部低剂量CT扫描中的应用

目的：探讨低管电流联合iDose4迭代重建技术应用于儿童胸部低剂量CT扫描的可行性。方法：连续88例行胸部CT平扫患儿随机分为2组，分别采用常规剂量（50 mAs）和低剂量（25 mAs）扫描。常规剂量组行滤波反投影（FBP）重建，记为A组；低剂量组分别行FBP、iDose4-1、iDose4-3、iDose4-5迭代重建（IR），依此记为B、C、D、E组。测量并计算每组图像的CT值、噪声、信噪比以评价图像客观质量；由2名副主任医师职称的放射诊断医师按5级评分法对图像进行主观质量评价；记录CT扫描仪剂量报告中提供的容积CT剂量指数（CTDIVOL）和剂量长度乘积（DLP），并计算有效剂量（ED）。对图像主客观质量及辐射剂量进行统计学分析。结果：低剂量组ED较常规剂量组降低52%，25 mAs联合FBP重建组图像主客观质量较常规剂量组降低且为低剂量组中最低（P＜0.05）；25 mAs联合iDose4-1迭代重建组图像主客观质量不及常规剂量组（P＜0.05）；25 mAs联合iDose4-3迭代重建组图像主客观质量与常规剂量组间差异无统计学意义（P＞0.05）；25 mAs联合iDose4-5迭代重建组图像主客观质量优于常规剂量组（P＜0.05）。结论：儿童胸部低剂量CT扫描时，采用25 mAs联合iDose4-3迭代重建技术，可获得与常规剂量组相当的图像质量，同时使辐射剂量降低52%。

Applied research of iterative reconstruction technique in the low-dose chest CT scans of children

Objective: To explore the feasibility of low tube current combined with iDose4 iterative reconstruction technique in the low-dose chest CT scans of children. Methods: Eight-eight children continuously underwent routine chest CT scan were divided into two groups using conventional dose (50 mAs) and low dose (25 mAs) scan, respectively. Routine dose group underwent filtered back projection (FBP) reconstruction, record as group A, low dose group was performed FBP, iDose4-1, iDose4-3, iDose4-5 iteration reconstruction (IR), and so referred to as group B, C, D, E. Measured and calculated CT value, noise, signal to noise ratio of each group images in order to evaluate the quality of the images objectively; quality of images was assessed according to five levels rating method by two diagnostic radiology physicians of deputy chief physician title; recorded volume CT dose index (CTDIVOL) and dose length product (DLP) provided by CT scanner dose reports, and calculated the effective dose (ED). Subjective and objective images quality and radiation dose were statistically analyzed. Results: Compared with routine dose group, effective dose (ED) of low dose group decreased by 52%. Subjective and objective quality of images of group B, the worst quality of low dose groups, was less than that of routine dose group (P<0.05), subjective and objective quality of images of group C was less than that of routine dose group (P<0.05), no significant statistical difference was existed between group D and group A in subjective and objective quality of images (P>0.05), subjective and objective quality of images of group E was better than that of group A (P<0.05). Conclusion: When low-dose chest CT scans of children are taking, 25 mAs tube current combined with iDose4-3 iterative reconstruction technique can obtain the same quality of images as routine dose group, while the radiation dose is reduced by 52%.