呼吸时相和模体位置对4D-CT图像均匀性的影响  

Effects of respiratory phase and phantom position on uniformity of 4D-CT image

作　　者：时飞跃[1,2] 秦伟[1] 陈飞[1] 赵环宇[1] 金洵[3] SHI Feiyue;QIN Wei;CHEN Fei;ZHAO Huanyu;JIN Xun(Radiation Therapy Center,Nanjing First Hospital,Nanjing Medical University,Nanjing 210006,China;Center of Medical Physics,Nanjing Medical University,Nanjing 210029,China;the Second Clinical Medical College,Nanjing University of Chinese Medicine,Nanjing 210023,China)

机构地区：[1]南京医科大学附属南京医院(南京市第一医院)肿瘤放疗中心,江苏南京210006 [2]南京医科大学医学物理研究中心,江苏南京210029 [3]南京中医药大学第二临床医学院,江苏南京210023

出　　处：《中国医学物理学杂志》2020年第1期65-68,共4页Chinese Journal of Medical Physics

基　　金：国家自然科学基金青年科学基金(81603674);江苏省自然科学基金青年基金(BK20161049)

摘　　要：目的:通过分析Catphan模体CTP486模块的四维CT(4D-CT)图像,研究呼吸时相和模体位置对4D-CT图像均匀性的影响。方法:使用西门子Sensation Open CT模拟机和瓦里安RPM系统,获取Catphan 504模体CTP486模块的4DCT图像。对3种模体位置情形进行研究。情形A:模体悬空放置;情形T:模体下有一个碳纤维CT平板床;情形B+T:模体下有一个碳纤维固定底板和一个CT平板床。每种情形重复3次测量。使用DoseLab放疗验证软件分析4D-CT图像,得到图像均匀性值(U)。对每一套4D-CT重建10个呼吸时相(0%,10%,⋯,90%)的CT图像序列。对U值进行统计分析和比较研究。结果:4D-CT所有CT序列的U值均小于5 HU。每种情形得到30个U值数据,情形A、情形T和情形B+T 3种情形U值分别为(1.44±0.79)、(1.91±0.91)和(1.99±0.77)HU。统计U值对应的4个边缘感兴趣区(ROI)出现的次数和比例,情形T中ROI 22(9点钟方向)出现13次(占比43.33%),情形B+T中ROI 23(12点钟方向)出现13次(占比43.33%)。结论:本研究中4D-CT的图像均匀性满足使用要求,不同呼吸时相4D-CT的图像均匀性值不同,模体摆放位置对4D-CT的图像均匀性有一定影响,碳纤维CT平板床和固定底板的存在使4D-CT的图像均匀性变差。Objective To investigate the effects of respiratory phase and phantom position on the uniformity of four-dimensional computed tomography(4D-CT)images by analyzing the 4D-CT image of the CTP486 module in Catphan phantom.Methods Siemens Sensation Open CT simulator and Varian RPM system were used to obtain the 4D-CT images of CTP486 module in Catphan 504 phantom.The following 3 cases in which the phantom position was different were utilized to carry out this study.In Case A,the Catphan phantom was hung in the air;in Case T,a carbon fiber CT flat table was placed under the phantom;and in Case B+T,a carbon fiber immobilization baseplate and the CT flat table were placed under the phantom.Three measurements were implemented for each case.DoseLab radiotherapy verification software was used to analyze the 4D-CT images,and the image uniformity(U values)were obtained.Ten series of CT were reconstructed for 10 respiratory phases(0%,10%,⋯,90%)for each 4D-CT measurement.Statistical analysis and comparative study were conducted on U values.Results All the U values of 4D-CT were smaller than 5 HU.For each case,30 U values were obtained.The U values in CaseA,Case T and Case B+T were(1.44±0.79),(1.91±0.91)and(1.99±0.77)HU,respectively.The numbers of times and proportions of the occurrence of 4 peripheral regions of interest which were corresponding to U values were analyzed.There were 13 ROI 22(9 o'clock position)in case T,with a proportion of 43.33%,and 13 ROI 23(12 o'clock position)in Case B+T,with a proportion of 43.33%.Conclusion The uniformity of 4D-CT images meets the requirements.The uniformity values of 4D-CT images for different respiratory phases are different.The phantom position has certain effects on the uniformity of 4D-CT images,and the existence of carbon fiber CT flat table and immobilization baseplate reduces the uniformity of 4D-CT images.

关 键 词：四维CT 图像均匀性 呼吸时相 模体位置 

分 类 号：R811.1[医药卫生—放射医学] R318[医药卫生—临床医学]