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目的 探讨迭代重组iDose4技术和基于模型的全迭代重组(IMR)技术在胃肠道肿瘤术后低剂量随访中的应用价值,并比较迭代重组iDose4和IMR对图像质量的影响.方法 将30例胃肠道肿瘤术后患者纳入此项研究.在初诊和6个月后复诊时分别进行腹部CT平扫和增强(常规剂量和低剂量)扫描,采用滤波反投影(FBP)技术重组常规剂量扫描图像门静脉期原始数据,采用迭代重组iDose4技术和IMR技术重组低剂量扫描图像门静脉期原始数据,得到3组图像,包括A组(常规剂量组)、B1组(低剂量iDose4组)、B2组(低剂量IMR组),将门静脉期扫描数据作为研究对象,对图像进行客观和主观分析,客观分析包括测量肝脏的CT值,噪声及信噪比(SNR),主观分析包括对图像进行质量评分,并比较辐射剂量.结果 低剂量扫描较常规剂量扫描辐射剂量平均降低了51.47％(P＜0.05).图像主观评分差异无统计学意义(P＞0.01),三组图像均能满足诊断要求.图像客观评价中,三组图像CT值相仿(P＞0.05),差异无统计学意义.三组图像的噪声、SNR值和对比噪声比(CNR)值之间的差异有统计学意义(P＜0.05),B1组较A组之间图像噪声和SNR值之间的差异均无统计学意义(P＞0.05),B2组较A组图像噪声明显降低、SNR值明显提高,差异均有统计学意义(P＜0.01),B1组与B2组较A组CNR值均提高,差异均有统计学意义(P＜0.01),B2组提高更显著,且B1与B2组之间差异有统计学意义(P＜0.01).结论 采用迭代重组iDose4技术和IMR技术,对胃肠道肿瘤患者术后进行低剂量CT随访,在大幅降低辐射剂量的同时均能保证图像质量可满足诊断要求,并且迭代重组IMR技术较iDose4技术的图像噪声低、图像质量高.“,”Objective To evaluate the application of the hybrid iterative reconstruction techniques algorithm (iDose4)and iterative model reconstruction(IMR) technique at low dose CT scan,and to compare the image quality of IMR with iDose4 for response assessment of post-operative gastrointestinal tumor evaluation.Methods 30 cases with post-operative gastrointestinal tumors were retrospectively analyzed.These 30 cases underwent dynamic enhanced CT scan at routine dose and followed up with dynamic enhanced CT scan at low dose 6 months later.Portal vein phases of routine and low dose scanning data were taken as the research object.Routine dose CT images were reconstructed with filtered back projection (FBP),and low dose CT images were reconstructed with iDose4 and IMR.3 data sets were obtained:GroupA (routine doseFBP),Group B1 (low dose-iDose4) and GroupB2 (low dose-IMR).Images were evaluated for objective analysis of hepatic CT value,noise,signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR) as well as subjective analysis of image quality scores,and to statistically compare the radiation dose.Results Compared with routine dose scanning,low dose scanning reduced radiation dose by 51.47％ and the differences were statistically significant(P ＜0.05).Image subjective scores:without significant statistical differences(P ＞ 0.01) and these three groups of images all met the diagnostic requirement.In the objective evaluation,the hepatic CT value of these three groups of images were similar without significant statistical differences(P ＞ 0.05).Increased image noise and decreased SNR were documented in Group B1 compared with Group A(P ＞0.01),while decreased image noise and increased SNR were documented in Group B2 compared with Group A (P ＜0.01).Compared with Group A,the CNR of Group B1 and Group B2 both increased(P ＜ 0.01),and Group B2 increased more significantly than Group B1 (P ＜ 0.01).Conclusion Significant radiation dose reduction and steadily maintained image quality can be achieved by using low dose scanning combined with iDose4 and IMR.Compared with iDose4,IMR significantly reduces the image noise and enhances image quality for response assessment of gastrointestinal tumor evaluation.