目的:通过动态模具定量分析瞬时双能成像技术在呼吸运动状态下,其单能量图像质量的可靠性以及物质密度测量的精准性.方法:采用定量动态分析模具,运动参数设定:上下呼吸运动幅度选取士2mm,±6mm和±8mm,呼吸运动频率选择静止状态,5次/min,10次/min和15次/min.8支内径为18mm的试管,分别装有不同浓度的碘对比剂和生理盐水混合溶液,浓度依次为:0.5,1,0,2.0,5.0,10.0,20.0.30.0.50.0(mg/ml).试管置于模型外周.利用Discovery CT750 HD能谱CT瞬时能量切换技术,生成单能量图像和密度图像.由3名高年资主治医师或高级职称医师判断运动状态下获得的图像质量并计算运动误差,同时在碘密度图像上测量试管内的碘密度值.统计学比较采用Mann-WhitneyU检验,P＜0.05为差异具有统计学意义.结果:随运动频率的增加,单能量图像质量评分与静止状态相近,运动状态下的内径测量值与静止状态相比无统计学差异.碘浓度测量的误差率与运动的振幅和频率未呈现相关性,与标准值相比无统计学差异(P＞0.05).平均测量误差率5.6％,可满足定量测量的需要.结论:模具研究表明0.5ms时间分辨率的瞬时双能成像在特定呼吸运动下可准确成像,并提供精确的基物质密度图像.%Objective:To evaluate the effect of breathing motion on the quality of monochromatic image and accuracy of basis density image reconstructed through kVp switching technique using a dynamic phantom. Methods:The motional altitude of dynamic phantom was set as±2 mm. ±6 mm and±8mm, and motional frequency was 5. 10.15 beats per minute. Eighteen tubes (diameter. 18 mm) were filled with iodine solution of different density (mg/ml). Which were 0. 5. 1. 0. 2.0. 5.0. 10. O.s 20. 0. 30.0. 50.0. Repectively. All tubes were embeded in phantom's circumference and the phantom was scaned using kVp switching technique (GSI). keV monochromatic images and basis density images were reconstructed based on GSI raw data. Image quality of keV images and accuracy of density images were assessed by three experienced doctors. Mann-Whitney U method was used for statistical analysis. Results: As for image quality of monochromatic images, no statistal difference was found between motion status and rest status ( P >0. 05). The accuracy error of motion status was 5.6% and didn't show statistical difference compared with standard value ( P >0. 05). Conclusion:kVp switching technique of 0. 5ms period can provide us with high quality keV images and accuracy density images on condition that breathing motion occurs.
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