三种阈值下勾画非小细胞肺癌PET图像靶区及影响的研究  

Impact of three threshold segmentation of ^18FDG PET image on target volume delineation and radiotherapy treatment planning of non-small cell lung cancer

作　　者：张碧媛[1] 蒋国梁[1] 胡伟刚[1] 夏冰[1] 章英剑[2] 姚之丰[2] 傅小龙[1] 

机构地区：[1]复旦大学附属肿瘤医院放疗科复旦大学上海医学院肿瘤学系,上海200032 [2]复旦大学附属肿瘤医院放疗科复旦大学上海医学院核医学科,上海200032

出　　处：《中华放射肿瘤学杂志》2008年第3期192-197,共6页Chinese Journal of Radiation Oncology

基　　金：卫生部临床重点学科项目基金资助项目[卫规财发（2004）468号],上海市科委重点项目基金资助项目（34119814）,复旦大学研究生创新基金

摘　　要：目的比较不同阈值对^18FDG PET-CT图像中非小细胞肺癌靶区勾画及放疗计划可能产生的影响。方法选择CT图像上原发灶边界清楚的、呼吸动度≤5mm的非小细胞肺癌8例，注射^18FDG后1h行PET扫描并以CT图像作衰减校正。以CT图像勾画的大体肿瘤体积（GTVCT）为标准，比较PET图像上用3种阈值条件[即肿瘤内最大像素值的42％（42％Imax（total））、本底平均像素值＋肿瘤内最大像素值与本底平均像素值的差值的20％（Iback＋20％Imax-back（max））和本底平均像素值＋肿瘤内每层最大像素值与本底平均像素值的差值的20％（Iback＋20％Imax-back（slice）]勾画的GTV（计为GTV42％、GTV20％。。和GTV20％ slice）与GTVCT差异及对GTVCT覆盖率的差异。以GTVCT、GTV42％、GTV20％max、GTV20％slice三维外放1cm为计划靶体积，分别计为PTVCT、PTV42％、PTV20％max、PTV20％slice。对不同PTV设计三维适形放疗计划，并均给予靶区剂量66Gy分33次6．6周完成。比较以不同PTV设计的计划中，PTVCT内接受〈95％处方剂量的体积（VPTV）及肺V20，并推算可能产生的TCP和肺NTCP的差异。结果GTV42%、GTV20%max,GTV20%slice与GTVCT的中位体积差分别为-54．1％，-21．5％和5．3％，三者对GTVCT的覆盖率中位数分别为45．9％、78．0％和95．3％（F=57．50，P〈0．01）。以不同PTV设计放疗计划时，PTV42%的中位VPTV为7．5％，由此可能导致TCP中位下降1％。PTV20%max和PTV20%slice的中位VPTV分别为1．3％和0．0％，其TCP与PTVCT的相似，与PTV42%的不同。三者的肺V20和肺NTCP与PTVCT的相似。结论层面化阈值条件Iback＋20％Imax-back（slice）可能是PET图像用于肺癌靶区勾画的较准确阈值，该阈值不依赖于预先由CT提供的肿瘤体积信息，可望用于伴有肺不张的非小细胞肺癌的靶区勾画。Objective To evaluate the accuracy of different threshold segmentation of ^18FDG PET for target volume delineation of non-small cell lung cancer（NSCLC） and the potential influence on radiotherapy treatment planning. Methods Eight NSCLC patients who had tumor with clear margin on CT scan and the amplitude of tumor movements not more than 5 mm were enrolled. PET scans were carried out at 1 h after intravenous injection of ^18FDG with CT image for attenuation revisement. Gross target volume （GTV） delineated on CT image （GTVcT） was used as the standard. Then, GTVs were delineated on PET image with three different threshold segmentation of 42% Imax（total） （42% of maximum voxel intensity within the tumor） ,thick ＋ 20% Imax-back（max） （ mean background intensity ＋ 20% of normalized background-subtracted maximum voxel intensity within the tumor） and Iback ＋ 20% I back（slice） （mean background intensity ＋ 20% of normalized background-subtracted maximum voxel intensity of each slice within the tumor） ,the corresponding GTV was named as GTV42% , GTV20%max and GTV20%slice. Both the size of GTV42% , GTV20%max, GTV20%slice and GTVCT, and the coverage over GTVCT for each GTV were compared. A three dimensional margin of 1 cm were added to GTVCT, GTV42%, GTV20%max and GTV20%slice to form corresponding PTVCT, PTV42%, PTV20%max and PTV20%slice.Three dimensional conformal radiotherapy treatment plans were designed based on PTVCT, PTV42% , PTV20%max and PTV20%slice respectively for each patient. The prescription dose of all PTVs was 66 Gy in 33 fractions in 6.6 weeks. Both the volume accepting dose less than 95% of prescription dose within PTVCT （ VPTV ） and the lung V20 were compared among the four plans based on different PTVs. Tumor control probability（TCP） as well as lung normal tissue complication probability （NTCP） were also compared. Results Eight patients were enrolled in this study. Median deviation of volume between GTVPET and GTVCT were - 54. 1%, - 21.5% and 5.3% for GT

关 键 词：癌 非小细胞肺/放射疗法 靶区勾画 正电子发射型 体层摄影术 

分 类 号：R686[医药卫生—骨科学]