前列腺癌放疗时CBCT使用频率和匹配策略的剂量学分析  

Dosimetric analysis of CBCT imaging frequency and matching strategy in prostate cancer radiotherapy

作　　者：高研 高献书[1] 马茗微 任雪盈 陈佳琰 马琳 黄磊[1] 尚士钰 Gao Yan;Gao Xianshu;Ma Mingwei;Ren Xueying;Chen Jiayan;Ma Lin;Huang Lei;Shang Shiyu(Department of Radiotherapy,Peking University First Hospital,Beijing 100034,China)

机构地区：[1]北京大学第一医院放射治疗科,北京100034

出　　处：《中华放射肿瘤学杂志》2024年第8期733-739,共7页Chinese Journal of Radiation Oncology

基　　金：中央高水平医院临床科研业务费(北京大学第一医院科研种子基金项目)(2023SF04);中华国际医学交流基金会肿瘤精准放疗星火计划(2019-N-11-07、2019-N-11-08);北京市自然科学基金-海淀原始创新联合基金(L232126)。

摘　　要：目的评价前列腺癌图像引导放疗时锥形线束CT(CBCT)的使用频率和匹配策略对靶区和危及器官剂量学参数的影响。方法回顾性分析北京大学第一医院2022年6月—2023年5月收治的21例前列腺癌根治性放疗患者的561套每日CBCT图像,患者均接受中等分割容积弧形调强放疗(VMAT),剂量为70 Gy分25次,2.8 Gy/次。根据不同图像引导方式和频率,校准摆位误差后将计划CT刚性配准到CBCT,CT值和结构通过形变配准算法传播到CBCT,根据形变矢量场将每日剂量映射到计划CT进行剂量累加。将每日在线CBCT验证的实际累积剂量与每周CBCT方案(第1-3、6、11、16、21天CBCT扫描)进行比较。比较基于骨匹配与基于软组织匹配(自动骨匹配后手动前列腺匹配并最终以直肠前壁为主做微调)两种匹配方式的摆位误差及剂量学参数。非正态分布的计划剂量和累积剂量之间的剂量学参数采用Wilcoxon符号秩和检验进行分析,符合正态分布的移床值和平均剂量参数采用配对t检验进行分析。结果与每日CBCT图像引导相比,每周方案的CTV_(D)98%[(69.08±1.58)∶(65.24±3.64)Gy,P<0.001]明显减少。采用骨匹配的CTV_(D)98%为(69.27±2.14)Gy,但直肠高量较高:V60 Gy为3.18%±3.10%、V65 Gy为0.77%±1.23%。采用软组织匹配方案的靶区覆盖率足够,CTV_(D)98%为(69.08±1.58)Gy;且直肠高量区剂量的百分体积明显减少,V60 Gy为2.02%±2.42%,V65 Gy为0.34%±0.68%。结论中等分割前列腺癌放疗,每日CBCT图像引导的靶区覆盖度优于每周方案。自动骨匹配后手动前列腺匹配并最终依据直肠前壁做微调的匹配策略,能在保证靶区覆盖率前提下较好地保护直肠。ObjectiveTo evaluate the effects of different imaging frequencies and matching strategies of cone-beam computed tomography(CBCT)on dose-volume parameters in target and organs at risk(OAR)during image-guided radiotherapy for prostate cancer.MethodsA total of 561 sets of CBCT images from 21 patients treated with radical prostate radiotherapy who were admitted to Peking University First Hospital from June 2022 to May 2023 were retrospectively analyzed.All patients received volumetric intensity modulated arc therapy(VMAT)at a prescribed dose of 70 Gy divided into 25 times,2.8 Gy per time.Clinical target volume(CTV)and OAR were delineated by the same oncologist on each CBCT image.The planned CT(pCT)was rigorously registered to CBCT after calibration of positioning errors according to different image guidance modes and frequencies,and CT values and structures were propagated to CBCT through deformable image registration(DIR).The daily dose was mapped to pCT according to the deformation vector field(DVF)for dose accumulation.The actual cumulative dose of daily online CBCT validation was compared with the weekly CBCT validation regimen(days 1,2,3,6,11,16 and 21 online imaging).The dosimetric comparison was also made between bone-based matching and soft tissue-based matching(after automatic bone-based matching,manual prostate-based matching was performed and fine-tuning was made regarding the anterior wall of rectum).Wilcoxon signed rank-sum test was utilized to analyze dose-volume parameters between planned and cumulative doses that exhibited non-normal distribution,while paired t-test was employed for assessing shift values and average dose parameters that demonstrated normal distribution.ResultsCompared with daily CBCT image guidance,the CTV_D 98%in weekly CBCT was significantly reduced[(69.08±1.58)vs.(65.24±3.64)Gy,P<0.001].The CTV_D 98%of bone-based matching was(69.27±2.14)Gy,but the high-dose volume of the rectum were significantly increased:V 60 Gy was 3.18%±3.10%,V 65 Gy was 0.77%±1.23%.The target area covera

关 键 词：前列腺肿瘤 放射疗法 根治性 图像引导 剂量学差异 

分 类 号：R737.25[医药卫生—肿瘤]