Dosimetric analysis of CBCT imaging frequency and matching strategy in prostate cancer radiotherapy
10.3760/cma.j.cn113030-20240202-00042
- VernacularTitle:前列腺癌放疗时CBCT使用频率和匹配策略的剂量学分析
- Author:
Yan GAO
1
;
Xianshu GAO
;
Mingwei MA
;
Xueying REN
;
Jiayan CHEN
;
Lin MA
;
Lei HUANG
;
Shiyu SHANG
Author Information
1. 北京大学第一医院放射治疗科，北京 100034
- Keywords:
Prostatic neoplasms;
Radiotherapy, radical;
Image guidance;
Dosimetric difference
- From:
Chinese Journal of Radiation Oncology
2024;33(8):733-739
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To 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.Methods:A 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. Results:Compared 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 coverage using soft tissue-based matching is sufficient, with a CTV_D 98% of (69.08±1.58) Gy. And the percentage volume of high-dose volume of the rectum was significantly reduced, with V 60 Gy being 2.02%±2.42% and V 65 Gy being 0.34%±0.68%. Conclusions:In prostate cancer patients undergoing moderately-fractionated radiotherapy, daily CBCT image guidance demonstrates superior target coverage compared to a weekly scheme. Soft tissue-based matching, which is automatic bone-based matching followed by manual soft tissue-based matching and fine-tuning according to the anterior rectal wall, offers better rectal protection while maintaining target coverage.
