Karl和RIO迭代重建算法对肾实质及肾动脉CT图像质量的影响

Effects of Karl and RIO iterative reconstruction algorithms on CT image quality of renal parenchyma and artery

目的:探讨Karl和RIO迭代重建算法对肾实质及肾动脉CT图像质量的影响。方法:回顾性收集行腹部增强扫描且后期采用3种方式[滤波反投影重建(FBP)、Karl、RIO]行图像重建的47例患者。在动脉期不同重建方式图像同一层面勾画ROI测得主动脉、双侧肾动脉的CT值和噪声值(SD值)、双侧肾髓质、双侧肾皮质、单侧竖脊肌CT值,以及皮下脂肪SD值,并计算SNR、CNR。对3种重建方式图像的血管边缘光滑程度和肾动脉下2级分支显示情况进行主观评分。采用Shapiro-Wilk方法行正态分布检验,应用Wilcoxon检验比较不同重建方式下肾动脉及肾实质的图像质量差异性,并采用Mann-Whitney U检验比较不同体型同一重建方式的图像质量及主观评价图像质量的差异性。结果:主动脉及双侧肾动脉不同重建方式的SNR和CNR差异均有统计学意义(均P<0.001)。双侧肾实质Karl与FBP及Karl与RIO的SNR和CNR差异均有统计学意义(均P<0.05)。不同体型组FBP主动脉图像的SNR和CNR,以及3种算法左肾髓质图像的CNR差异有统计学意义(均P<0.05)。在主观评价肾动脉边缘光滑程度方面,FBP与Karl及FBP与RIO差异均有统计学意义(均P<0.001)。结论:RIO和Karl迭代重建算法在主动脉及双侧肾动脉成像中,图像质量均优于FBP,其中RIO最优;但在肾脏皮髓质成像中,Karl的图像质量优于FBP及RIO。RIO在肾动脉图像质量评估中可替代Karl,能够提高图像质量或降低辐射剂量。

Objective:To investigate the effects of Karl and RIO iterative reconstruction algorithm on renal parenchyma and renal artery on CT image quality.Methods:A retrospective collection of 47 cases of images that underwent abdominal enhancement examinations and used three methods of[filter back-projection(FBP),Karl,RIO]in the later stage was made.The CT values and SD values of the aorta and bilateral renal arteries,CT values of bilateral renal cortex and medulla and unilateral erector spinae muscle,and SD value of subcutaneous fat were measured by delineating ROI at the same level of images with different reconstruction methods in the arterial phase,and SNR and contrast-to-noise ratio(CNR)were calculated.Shapiro-Wilk method was used for normal distribution test,Wilcoxon test was used to test the difference of image quality of arteries and renal parenchyma under different reconstruction methods,and Mann-Whitney U test was used to test the difference of image quality of different body types with the same reconstruction method.Results:There were significant differences in SNR and CNR of aorta and bilateral renal arteries between the three different reconstruction modes(all P<0.001).The SNR and CNR of bilateral renal parenchyma were significantly different between Karl and FBP and RIO(all P<0.05).The SNR and CNR of different body types of FBP on the aortic image,and the CNR of the three algorithms on the left renal medulla image were statistically significant(all P<0.05).In subjective evaluation of renal artery margin smoothness,there were significant differences between FBP and Karl and RIO(both P<0.001).Conclusions:RIO and Karl iterative reconstruction algorithms can improve CT image quality,compared with FBP in aortic and bilateral renal artery imaging,especially RIO.But in the imaging of renal cortex and medulla,the image quality of Karl is better than that of FBP and RIO.RIO can replace Karl in evaluating renal artery image quality,can improve image quality or reduce radiation dose.