宽体探测器联合全模型实时迭代重建在肥胖患者上腹部扫描中的应用

Abdominal CT with low radiation dose in obese patients： application of wide-detector helical CT combined with adaptive statistical iterative reconstrnction-V （ASIR-V）

目的 探讨宽体探测器联合全模型实时迭代重建技术（ASIR-V）在肥胖患者上腹部低辐射剂量扫描中的应用价值。方法 根据体模实验找出常规上腹部扫描（管电压为120 kVp，噪声指数为10 HU）最佳前置及后置ASIR-V比例；在体模实验基础上，前瞻性收集需行上腹部CT增强的87例肥胖患者（体质量指数≥30 kg/m2），依随机数表法分为试验组（43例）和对照组（44例）。试验组采用宽体探测器（80 mm）CT联合前置40% ASIR-V行上腹部双期增强扫描获得A1组图像（默认为后置40% ASIR-V），再联合60%后置ASIR-V技术重建获得A2组图像。对照组采用常规探测器CT（40 mm）扫描后联合40%自适应统计迭代重建技术（ASIR）重建获得B组图像。比较试验组和对照组的辐射剂量、图像的对比噪声比（CNR）、图像噪声和主观评分（5分制法）。结果 常规上腹部扫描最佳前置及后置ASIR-V比例分别为40%及60%。试验组的有效剂量E为（4.55±0.95）mSv，低于对照组的（9.58±2.04）mSv（t=-14.773，P〈0.001）。A2组除双期肝脏外，各部位CNR均高于A1及B组（q=2.160-3.209，P〈0.05），双期图像噪声低于A1及B组（q=-4.212--3.202，P〈0.05），双期总体图像质量评分高于A1及B组（Z=-5.155--2.561，P〈0.05）。A1组双期各部位CNR及图像噪声与B组差异均无统计学意义（P〉0.05），双期总体图像质量评分低于B组（Z=-3.298--3.030，P〈0.05）。A组双期图像质量评分均〉3分，均能满足临床诊断需求。结论 肥胖患者采用宽体探测器联合前置40% ASIR-V技术，可比常规探测器扫描减少约53%的辐射剂量；联合后置ASIR-V重建技术，可在保持或提高图像CNR的同时优化总体图像质量。

Objective To investigate the value of wide-detector helical CT combined with adaptive statistical iterative reconstruction-V （ASIR-V） in the low radiation dose CT examination of upper abdomen in obese patients. Methods In the first phantom experiment part, the optimal percentage of pre-and post-ASIR-V of abdominal scanning （120 kVp, NI=10 HU） were explored. The second human experiment was performed based on the phantom study, and our institutional review board approved this prospective study, each participant provided written informed consent. 87 obese patients （body mass index, BMI ≥ 30 kg/m2） underwent contrast-enhanced abdominal CT scan were randomly divided into two scan protocols[protocol A：n=43, 120 kVp, detector coverage of 80 mm, 40% pre-ASIR-V （group A1） and combined with 60% post-ASIR-V （group A2） respectively; protocol B, n=44, 120 kVp, detector coverage of 40 mm, 40% ASIR （group B）]. Quantitative parameters[image noise and contrast-to-noise ratio （CNR）] and qualitative visual parameters （overall image quality as graded on a 5-point scale） were compared. Weighted effective dose （E） were assessed. Results The optimal percentage of pre-and post-ASIR-V of abdominal scanning were 40% and 60%, respectively. The effective radiation dose in protocol A[（4.55 ±0.95） mSv] was decreased for 53% as compared with protocol B[（9.58 ±2.04） mSv] （t=-14.773, P〈0.001）. During the arterial phase and portal venous phase, except for the CNRs of liver, Group A2 showed higher CNRs （q=2.160-3.209, P〈0.05）, lower image noise（q=-4.212--3.202, P〈0.05）, and higher overall image quality scores（Z=-5.155--2.561, P〈0.05） as compared with group A1 and group B. Group A1 showed similar CNRs, similar image noise（P〉0.05）, and lower overall image quality scores（Z=-3.298--3.030, P〈0.05） than group B. The overall image quality scores in group A were all greater than 3 point and met the clinical diagnostic level. Conclusions Compared with stand-detector helical CT in obese patients, the wide-detector helical CT combined with 40% pre-ASIR-V could reduce the radiation dose by 53%, and improve overall image quality by combining post-ASIR-V technique.