优化前后置全模型迭代重建技术低剂量腹部CT扫描

Optimized combination of pre-and post-adaptive statistical iterative reconstruction-V in low dose abdominal CT scanning

目的观察全模型实时迭代重建技术(ASiR-V)对腹部CT图像质量和辐射剂量的影响,优化ASiR-V前置联合后置百分比方案。方法将160例接受上腹部CT扫描的患者随机分为试验组或对照组,各80例。试验组在平扫、动脉期、门静脉期和延迟期分别采用前置20%ASiR-V扫描联合后置20%、40%、60%、80%ASiR-V重建,前置40%联合后置40%、60%、80%,前置60%联合后置60%、80%及前置80%联合后置80%扫描及重建方法;对照组采用前置0%ASiR-V扫描,并分别采用FBP和后置20%、40%、60%和80%ASiR-V两种方式进行重建。对所有图像进行客观评价[噪声(SD)和CNR]和主观评分,并进行比较。结果试验组各期相CT剂量指数、剂量长度乘积及有效剂量均低于对照组(P均<0.001)。相同期相内,随后置迭代比例增加,SD值逐渐减小(P<0.01),而CNR值无变化或增加;试验组图像随后置ASiR-V(20%~60%)增高,图像主观评分增加,ASiR-V为80%时图像质量较差。试验组平扫前置20%联合后置40%、60%图像与对照组平扫ASiR-V重建图像、试验组动脉期前置40%联合后置60%图像与对照组动脉期ASiR-V重建图像质量评分差异无统计学意义(P均>0.05),其余试验组图像质量评分均小于对照组ASiR-V图像。结论一定比例ASiR-V重建可提高腹部CT图像质量,推荐使用ASiR-V前置40%联合后置60%扫描方案。

Objective To observe the impact of adaptive statistical iterative reconstruction-V （ASiR-V） on image quality and radiation dose in abdominal CT imaging, and to optimize combination of pre-and post-ASiR-V percentage. Methods Totally 160 patients underwent plain and contrast-enhanced abdominal CT were randomly divided into study group or control group （each n：80）. In study group, plain images were reconstructed with 20% pre-ASiR-V combined with 20%, 40%, 60% and 80% post-ASiR-V, the arterial phase images were reconstructed with 40% pre-ASiR-V combined with 40%, 60% and 80% post-ASiR-V, while the venous phase images with 60% pre-ASiR-V combined with 60% and 80% post-ASiR-V, and the delayed phase images with 80% pre-ASiR-V combined 80% post-ASiR-V. In control group, images were reconstructed with filtered back projection （FBP） and 0 pre-ASiR-V combined post-ASiR-V （20% in plain, 40% in arterial phase, 60% in venous phase and 80% in delayed phase imaing）. The objective parameters （image noise ESD] and CNR） and image quality scores were analyzed and compared. Results CT dose index, dose length product and effective dose of each phase in study group were lower than those in control group （all P〈0. 001）. In study group, with the increasing of post-ASiR-V percentage, SD values gradually decreased （P〈0.01）, and CNR gradually increased or did not change. With the increasing of post-ASiR-V （20 %-60 %）, image quality scores increased, and image quality of 80 % post- ASiR-V was low. In study group, image quality of 20% pre-ASiR-V combined 40% or 60% post-ASiR-V was similar to 20 % post-ASiR-V image in control group in plain, and that of 40 % pre-ASiR-V combined 60 % post-ASiR-V was similar to 40% post-ASiR-V image in control group in arterial phase （all P〉0.05）, while image quality scores of other combinations of pre- and post-ASiR-V percentages were lower than those in control group. Conclusion ASiR-V can improve abdominal CT image quality, and 40% pre-ASiR-V combined 60% post-ASiR-V is recommended.