基于迭代算法ASiR-V的CTU能谱与非能谱成像的对比研究:体模及临床研究

A Comparative Study of CTU with Energy⁃spectral Versus Non⁃energy⁃spectral Imaging Based on the Revolution CT Iterative Algorithm ASiR⁃V:A Phantom and Clinical Study

目的:通过体模预试验和临床研究,对比分析CT尿路成像(CTU)能谱与非能谱扫描图像质量及辐射剂量的差异,探究能谱扫描在保证图像质量前提下利用前置多模型迭代重建算法(ASi R-V)控制剂量的有效性。方法:(1)QSP Phantom体模预试验:采用80/140 kV(0.5 ms)切换能谱扫描、GSI辅助,NI=5,自动匹配相应的GSI模式,重建70 ke V,记作A-1组;非能谱扫描采用120 k V、自动毫安技术(NI=5),记作A-2组;固定毫安=365 m A,能谱扫描者记作B-1组,非能谱扫描(120 k V)者记作B-2组,均采用FBP重建。(2)临床研究:前瞻性收集CTU平扫+增强检查者45例。对照组:平扫采用120 kV、自动管电流调制扫描(NI=11),采用前置40%ASiR-V重建。实验组:增强三期均采用GSI模式,重建70 keV,打开GSI辅助(NI=11),自动选择最佳能谱参数扫描,动、静脉期及延迟期重建前置ASi R-V权重分别为30%、40%、50%(后置ASi R-V权重与之匹配)。对体模QSP Phantom及临床研究的能谱与非能谱扫描各组图像质量进行客观、主观评价,并记录每次扫描的检查辐射剂量,采用配对t检验和Wilcoxon秩和检验进行统计学分析。结果:(1)体模研究:自动毫安(NI=5),10、2.5 mg/mL及水试管在A-1组图像的SD值与A-2组无显著差异(P>0.05),20、5 mg/mL试管在A-1组图像的SD值稍高于A-2组(P<0.05),A-1组的CTDIvol较A-2组升高2.3%;固定毫安=365 mA,各目标试管在能谱B-1组图像中的SD值稍高于非能谱B-2组(P>0.05),B-1组的CTDIvol较B-2组降低36.3%。(2)临床研究:1)NI=11、ASi R-V权重相同(40%),能谱与非能谱图像的SD值无显著差异(P>0.05),图像主观评分均>4分,组间差异无统计学意义(P>0.05),能谱扫描的CTDIvol较非能谱升高6.06%(P>0.05);2)NI=11,30%、50%ASiR-V的能谱扫描与非能谱相比,各组间SD无显著差异(P>0.05),3组图像均满足影像诊断要求(>4分),相比40%非能谱扫描,30%能谱CTDIvol升高29.4%,50%能谱CTDIvol降低17.3%(P<0.05);(3)不同权重ASiR-V能谱图像的SD值组间无显著差异(P>0.05),辐射剂量随ASiR-V迭代强度增加而降低,相比于30%能谱扫描,40%、50%能谱CTDIvol依次降低22.0%、51.7%。结论:在自动毫安条件下,从体模预试验和临床研究,能谱成像图像质量及辐射剂量与非能谱成像相当;将能谱成像联合前置ASi R-V,在保证图像质量的同时可获得比非能谱更低辐射剂量的能谱图像,使其在临床中应用的效益最大化,具有良好的应用前景。

Purpose:To compare and analyze the differences in image quality and radiation dose between CT urography(CTU)with energy-spectrum and non-energy-spectrum scans in QSP Phantom and clinical studies,and to investigate the effectiveness of anterior adaptive statistical iterative reconstruction-V(ASiR-V)control dose of energy-spectrum scans under the premise of image quality assurance.Methods:(1)QSP Phantom pre-experiments were consisted of 4 groups.Group A-1:80/140 kV(0.5 ms)switching energy spectrum scan with GSI assist turned on,NI=5,automatic matching of the corresponding GSI mode,and 70 keV reconstruction;Group A-2:non-energy spectrum scan with 120 kV and automatic milliampere technique(NI=5);Group B-1:fixed milliampere=365 mA,energy-spectrum scan;Group B-2:non-energy-spectrum scan(120 kV),all the images were reconstructed with FBP.(2)Clinical study:45 cases of CTU plain scan and enhanced examinations were collected prospectively.1)Control group:flat-scan with 120 kV,automatic tube current modulation scan(NI=11),with anterior 40%ASiR-V reconstruction.2)Experimental group:all three phases of enhancement were reconstructed using GSI imaging mode with 70 keV,GSI assist turned on(NI=11),automatic selection of optimal energy spectrum parameters for scanning,and different weights of 30%,40%,and 50%of the reconstructed anterior ASiR-V in the arterial,venous,and delayed phases,respectively(the weights of the posterior ASiR-V in this study matched exactly with the anterior ASiR-V).Objective and subjective evaluation of image quality was performed for each group of energy-spectral and non-energy-spectral scans from the QSP Phantom and clinical studies,and the examined radiation dose for each scan was recorded,and the data were statistically analyzed using paired t-test and Wilcoxon rank sum test.Results:(1)Phantom study:automatic milliampere(NI=5),SD values of 10 mg/mL,2.5 mg/mL and water cuvettes in group A-1 images were with no significant difference from group A-2(P>0.05);SD values of 20 mg/mL and SD values of 20 mg/mL and 5 mg/mL cuvettes in group A-1 images were slightly higher than those in group A-2(P<0.05);compared to group A-2,CTDIvol in group A-1 was elevated by 2.3%;fixed milliampere=365 mA,SD values for each target cuvette were slightly higher in the energy-spectrum group B-1 images than those in the non-energy-spectrum group B-2 images(P<0.05),and CTDIvol in group B-1 was 36.3%lower than that in group B-2.(2)Clinical studies:1)NI=11,same weight of ASiR-V(40%),SD values for energy-spectrum images vs non-energy-spectrum images were with no significant difference(P>0.05),the subjective scores of the images were all greater than 4,there was no significant difference among groups(P>0.05),and the CTDIvol of energy spectrum scans was elevated by 6.06%when compared to non-energy spectrum(P>0.05).2)When NI=11,30%,50%ASiR-V of energy spectrum scans compared to non-energy spectrum,there was no significant difference in SD between groups(P>0.05),and the images of all 3 groups met the diagnostic imaging requirements(>4 points),and the CTDIvol was elevated by 29.4%for the 30%energy spectrum and decreased by 17.3%for the 50%energy spectrum when compared to the 40%nonenergy spectrum scan(P<0.05).3)There was no significant difference in SD between groups for the different weighted ASiR-V energy spectrum images(P>0.05).The examination radiation dose decreased with the ASiR-V iteration intensity increased,compared with the CTDIvol of 30%energy spectrum,the CTDIvol of weight 40%and 50%decreased by 22.0%and 51.7%,respectively.Conclusion:Under the automatic milliampere conditions,the image quality and radiation dose of energy spectral imaging are comparable to those of non-energy spectral imaging from body model pre-experiments and clinical studies;combining energy spectral imaging with anterior ASiR-V can obtain energy spectral images with lower radiation dose than non-energy spectral while ensuring image quality,which maximizes the benefits of energy spectra6l imaging in clinical.