迭代重建技术在肥胖患者肾上腺CT成像中的应用

目的? 将自适应迭代重建技术（ASiR）用于肥胖病人的肾上腺CT成像，旨在评价ASiR在降低辐射剂量和提高影像质量中的应用价值。方法? 收集200例肥胖病人并行肾上腺CT扫描，男112例，女88例，年龄17~78岁，平均（５４．２２±１８．６３）岁，分为2组，各100例。A组行常规剂量的滤过反投影（ＦＢＰ）重建，B组为降低剂量的ASiR?4个等级（未降低，分别降低30%、50%、100%）重建，所有重建图像传送至AW4.6工作站，分别由3名CT诊断医师采用双盲法对两组影像质量进行评价。采用t检验对比两组辐射剂量，单因素方差分析比较影像质量的客观指标（噪声、SNR、CNR）及主观评分，组间多重比较采用LSD-t检验。采用Kappa检验评价3名医师主观评分一致性。结果? A组与B组4个不同迭代等级的重建影像进行比较，B组中各重建的肾上腺噪声、肌肉噪声及脂肪噪声均随迭代等级升高而下降，SNR及CNR随迭代等级的升高而升高（P＜0.05）。其中，ASiR50%时各部位噪声、肾上腺SNR与FBP重建相近（P＞0.05）。3名医师主观评分为一致性较好（Kappa=0.76）。影像质量显示能力评分由高到低依次为ASiR100%、A组FBP、?ASiR50%、ASiR30%、ASiRNone（P＜0.05）。结论? ?在肥胖病人肾上腺CT成像中应用ASiR技术显著降低了辐射剂量，ASiR（50%~100%）所得影像质量近似或优于传统FBP。

Application of iterative reconstruction technique in CT imaging of adrenal gland in obese patients

Objebtive To apply adaptive statistical iterative reconstruction (ASiR) technique in CT imaging of adrenal gland in obese patients to reduce the radiation dose and improve the image quality. Methods Adrenal gland CT scans of 200 obese patients were collected, including male 112 cases, female 88 cases, age 17-78 years old, mean age 54.22± 18.63 years old. Classfied patients into 2 groups, 100 cases each. Group A underwent routine filtered back projection (FBP), and group B underwent ASiR using 4 grades (None, 30%, 50%, and 100%). The data of all patients were transmitted to the workstation (AW4.6), and were evaluated by three doctors with double-blind method. A t test was used to compare radiation dose two between the 2 groups. One way ANOVA with post hoc LSD-t test was used to compare the objective image quality indicators (noise, SNR, and CNR) and the subjective score. Kappa test was used to evaluate the consistency of subjective scores among the three doctors. Results Compared to the group A, the reconstructed image noise of the adrenal gland, muscle and fat were decreased with the increasing of the iterative rank, while SNR and CNR were increased with the increasing of the iteration level (P<0.05) in the group B. Among the sub-groups of group B, when ASiR 50%was used, the SNR, FBP, and reconstruction noise did not significantly differ at each region of adrenal gland (P>0.05). The subjective scores from three doctors were consistent well (Kappa=0.76). ASiR100%achieved the best image quality, followed by group A FBP, ASiR50%, ASiR30%, and ASiR None (P<0.05). Conclusion The ASiR technique in CT imaging of adrenal gland in obese patients could reduce the radiation dose. ASiR 50%~100%is comparable even better than FBP in image quality.