PET/CT联合4DCT在食管癌放疗中的应用

摘要

目的 分析标准摄取值(SUV)阈值下的正电子发射体层显像(PET)/CT和全时相4DCT在食管癌靶区勾画的相关性,探索能准确反映靶区空间运动的最优SUV值.方法 将该院初治的82例食管癌患者于同一天分别行PET/CT和4DCT扫描定位,选取不同SUV阈值(≥2.0、2.5、3.0、3.5)及最大SUV值的百分比(≥20％SUVmax、30％ SUVmax、40％SUVmax)勾画PET/CT靶区内大体肿瘤体积(IGTV) PET/CT,叠加各时相4DCT靶区得到包含所有呼吸状态的靶区IGTV10,对比两图像的靶区中心偏移、体积比和适形指数(CI),选出与4DCT靶区配准度相对较好的SUV值,并分析该阈值下靶区中心偏移、体积比和CI分别与IGTV10体积、IGTV10长轴径、头脚方向位移及空间运动位移的相关性.结果 SUV取2.0或20％ SUVmax时,4DCT和PET/CT图像靶区空间匹配程度较好.IGTVPET2.0、IGTVPET20％与IGTV10的靶区中心偏移在头脚方向位移和空间运动位移上均呈正相关(P＜0.05);体积比在IGTV10体积、IGTV10长轴径、头脚方向位移及空间运动位移间均无相关性(P＞0.05);CI在IGTV10体积和IGTV10长轴径上呈正相关,在头脚方向位移及空间运动位移上呈负相关(P＜0.05).结论 SUV取2.0和20％SUVmax时,PET/CT与全时相4DCT勾画食管癌靶区的体积相近,但在适形度上二者仍有一定偏差,应对PET/CT阈值及4DCT时相选取做进一步研究.%Objective To study the correlation of positron emission tomography/computed tomography (PET/CT) under different standardized uptake value (SUV) thresholds and full time four-dimensional computed tomography (4DCT) in esophageal carcinoma target delineation and explore the optimum SUV value that can accurately reflect the spatial movement of the target.Methods Eighty-two patients with esophageal cancer initial treatment in this hospital were respectively performed the scanning localization by PET/CT and 4DCT on the same day.Then different SUV thresholds (≥2.0,2.5,3.0,3.5) and the percentage of maximum SUV value (≥20％ SUV 30％ SUV 40％ SUVmax) were selected to delineate the internal gross target volume (IGTV) PET/CT in PET/CT,the ten phases of the 4DCT were collected to obtain the full time target IGTV10,the target center offset,volume ratio and conformity index (CI) were compared between the two images,the relatively good SUV value with the registration in 4DCT target was picked out,then the correlation between the target center offset,volume ratio and CI with the IGTV10 volume,long axial diameter of IGTV10,displacement of head-to-foot direction and spatial motion was analyzed.Results When the SUV threshold was 2.0 or 20 ％ SUV the spatial matching degree of 4DCT and PET/CT images was better.The head-to-foot direction displacement and special motion displacement in the target center offset of IGTVPET2.0,IGTVPET20％ and IGTV10 showed the positive correlation (P＜0.05);the volume ratio had no correlation with the IGTV10 volume,IGTV10 long axial diameter,head-to-foot direction displacement and special motion displacement (P＞0.05);CI had positive correlation with IGTV10 volume and IGTV10 long axial diameter,while had negative correlation with the head-to-foot direction displacement and special motion displacement (P＜0.05).Conclusion When SUV taking 2.0 or 20％ SUV the esophageal carcinoma target volume of PET/CT is similar to that of full time 4DCT,but there are still some deviations in the conformity index,therefore the PET/CT threshold value and 4DCT time phase selection should be further studied.