Effects of changes in bladder volumes derived from CT simulation on set-up errors during radiotherapy for prostate cancer
10.3760/cma.j.cn112271-20230414-00119
- VernacularTitle:前列腺癌放疗定位中膀胱体积的变化对摆位重复性的影响
- Author:
Zhanwei LI
1
;
Hong HUANG
;
Mengxue HE
;
Maosheng LIN
;
Chengguang LIN
;
Feng CHI
;
Wenyan YAO
;
Senkui XU
Author Information
1. 中山大学肿瘤防治中心放疗科，广州 510060
- Keywords:
Prostate cancer;
Intensity-modulated radiation therapy;
Cone beam CT;
Bladder volume;
Set-up error
- From:
Chinese Journal of Radiological Medicine and Protection
2023;43(12):986-990
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To explore the effects of bladder volumes from CT simulation on bladder volume consistency and set-up errors during radiotherapy for prostate cancer, aiming to provide a reference for clinical practice.Methods:A retrospective analysis was conducted for of 66 prostate cancer patients treated with intensity-modulated radiation therapy in the Sun Yat-sen University Cancer Center from August 2015 to November 2020. They underwent CT scan or radiotherapy after voluntarily holding in urine. Cone beam computed tomography (CBCT) scans were performed for them to measure their set-up errors in left-right (L-R), superior-inferior (S-I), and anterior-posterior (A-P) directions before each treatment. The bladder contours of the patients were delineated on CT simulation images and CBCT images. Accordingly, bladder volumes were calculated. Based on the calculated bladder volumes derived from the CT simulation images, the patients were divided into three groups: 18 cases in the 200-300 ml group, 24 cases in the 300-400 ml group, and 24 cases in the >400 ml group. Finally, this study analyzed the effects of bladder volumes derived from CT simulation on set-up errors and the changes of CBCT-derived bladder volumes relative to planned volumes during radiotherapy.Results:The bladder volumes in the 200-300 ml, 300-400 ml, and >400 ml groups during radiotherapy were reduced by 15%, 26%, and 32%, respectively. The pairwise comparison indicates statistically significant differences in the changes of bladder volumes among the three groups ( Z=3.43, 7.97, 4.83, P<0.05). Regarding the three-dimensional set-up errors, there were statistically significant differences in S-I set-up errors among the three groups ( H=26.72, P<0.05), but there was no statistically significant difference in L-R and A-P set-up errors ( P>0.05) among these groups. The 200-300 ml, 300-400 ml, and >400 ml groups exhibited S-I set-up errors of 0.00 (-0.20, 0.20) cm, 0.00 (-0.20, 0.30) cm, and -0.10 (-0.30, 0.20) cm, respectively. Therefore, the >400 ml group displayed larger the S-I set-up errors than other two groups, with statistically significant differences ( Z=4.17, 4.66, P< 0.05), while there was no statistically significant differences in S-I set-up errors between other two groups ( P> 0.05). Conclusions:Controlling the bladder filling volumes at 200-300 ml in CT simulation is beneficial for maintaining bladder volume consistency and reducing set-up errors of patients during radiotherapy.
