低剂量结合iDose迭代重建算法在上腹CT扫描中的应用

Application of low-dose combined with iDose iterative reconstruction in CT scan of upper abdomen

目的比较低剂量与常规剂量扫描滤波反投影(FBP)、i Dose1、i Dose3、i Dose5重建对上腹部CT图像质量影响的差异。方法按照就诊顺序,对60例患者行常规剂量上腹CT增强扫描,60例行低剂量上腹CT增强扫描。采用自动管电流调控技术,低剂量组门静脉期m As基准值较常规剂量组降低20%。采用FBP、i Dose1、i Dose3、i Dose5分别对两组门静脉期的图像进行重建。计算图像的噪声、信噪比(SNR)及对比噪声比(CNR)。两名具有5年以上工作经验的医师评价图像的主观质量(噪声、诊断可接受性、伪影及锐利度)。分别将常规剂量、低剂量组按照性别分为两组,记录容积CT剂量指数(CTDIvol)、剂量长度乘积(DLP),计算有效剂量(ED)。结果低剂量扫描结合i Dose重建后图像均能满足诊断要求,与常规剂量组相比,男性低剂量组CTDIvol、DLP、ED分别降低26.39%、26.71%、26.71%,女性分别降低24.52%、25.27%、25.27%。结论低剂量扫描结合i Dose迭代技术可以在满足图像诊断质量的前提下有效降低辐射剂量。

Objective To compare differences of reconstruction with filtered back projection（FBP）,iDosel,iDose3,and iDose5 on the quality of CT images of upper abdomen between low-dose CT scan and routine-dose CT scan.Methods According to the examination order,60 patients underwent the contrast-enhanced routinedose CT scan of upper abdomen and another 60 patients underwent the low-dose CT scan of upper abdomen.The automatic tube current technique was adopted and the mAs reference value of portal venous phase of the low-dose group was 20%lower than that of the routine-dose group.CT images of portal venous phase of two groups were reconstructed by filtered back projection,iDosel,iDose3,and iDose5.The noise,signal-to-noise ratio（SNR）,and contrast-to-noise ratio（CNR） of images were calculated.The subjective quality（noise,diagnostic acceptability,artifacts,and sharpness） of images was evaluated by 2 radiologists with work experience of more than 5 years.Patients of routine-dose group and low-dose group were divided into two subgroups according to the gender.Volume CT dose index（CTDIvol） and dose length product（DLP） were recorded and effective dose（ED） were calculated.Results Low-dose CT scan combined with iDose reconstruction could satisfy the diagnostic demand.Compared with the routine-dose group,CTDIvol,DLP,and ED of male patients of the low-dose group decreased 26.39%,26.71%,and 26.71%,respectively,while those of female patients of the low-dose group decreased 24.52%,25.27%,and 25.27%,respectively.Conclusion Lowdose CT scan combined with iDose iterative technique can effectively reduce the radiation dose while meeting the diagnostic quality of images.