胰腺癌放疗分次间解剖变化及自适应放疗研究

Study of inter-fractional variations and adaptive radiotherapy in pancreatic cancer

目的定量描述胰腺癌放疗分次间解剖位置变化及自适应放疗剂量优势。方法回顾分析图像引导放疗的10例胰腺癌患者的226套治疗当天CT图像，自动勾画软件勾画靶器官和危及器官轮廓后由经验丰富的医师修改。应用质心距离、最大重叠率和Dice系数定量分析分次间器官移位和变形。应用自适应放疗技术处理治疗当天CT图像，比较自适应治疗计划和校位治疗计划的剂量参数。结果胰腺癌放疗过程中胰头分次间解剖变化显著，经骨性或软组织对齐配准后胰头质心距离、最大重叠率和Dice系数分别为（7．8±1．3）mm、（87．2±8．4）％和（77．2±7．9）％。自适应治疗计划靶体积（PTV）包绕和危及器官保护方面均优于校位治疗计划，自适应治疗计划将校位治疗计划PTV的V100从（93．32±2．89）％提高至（96．03±1．42）％（t=2．79，P=0．008），同时将校位治疗计划的十二指肠V洲从（43．4±12．71）％降至（15．6±6．25）％（t=3．52，P=0．000）。结论自适应放疗能有效应对胰腺癌放疗中分次间的解剖变化，可提高胰腺癌放疗剂量，这为提高胰腺癌局部控制率带来了希望。

Objective To quantitatively characterize the inter-fractional anatomy variations and advantages of dosimetry for the adaptive radiotherapy in pancreatic cancer. Methods A tots] d 226 daily CT images acquired from 10 patients with pancreatic cancer treated with image-guided radiotherapy were analyzed retrospectively. Targets and organs at risk （OARs） were delineated by the arias-based automatic segmentation and modified by the skilled physician. Various parameters, including the center of mass （COM） distance, the maximal overlap ratio （MOR） and the Dice coefficient （DC）, were used to quantify the inter-fractional organ displacement and deformation. The adaptive radiation therapy （ART） was applied to handle the daily CT images. The dose distributions parameters from the ART plan were compared with those from the repesitioning plan. Results The inter-fractional anatomy variations of pancreas head were obvious in the pancreatic cancer irradiation. The mean COM distance, MOR and DC of pancreas head after the bony or soft tissue alignment and registration was （7.8 ±1.3 ） nun, （ 87.2 ±8. 4 ） % and （ 77.2 ± 7.9） % respectively. Compared with the repesitioning plan, the ART plan had better target coverage and OARs sparing. For example, the mean V100 of FIT was improved from （93.32 ± 2. 89） % for reposifioning plan to （96.03 ± 1.42）% for ART plan with t=2.79,P=0. 008 and the mean Vs0.4 for duodenum was reduced from （43.4 ±12. 71 ） % for the repeaitioning plan to （ 15.6 ± 6. 25 ） % for the ART plan with t = 3.52,P =0. 000. Conclusions The ART can effectively account for the obvious inter-fractional anatomy variations in pancreatic cancer irradiation and be used to escalate the radiotherapy dose for the pancreatic cancer, which will lead to a promising higher local control rate.