ESTRO 2024 - Abstract Book

S5488

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

Differences between two posture fixation methods in VMAT for cervical cancer

Pengfei Yang 1 , Zhichao Xie 1 , Zixuan Liu 1 , Junfeng Ai 1 , Zhaoming Peng 1 , Xin Li 1 , Zhe Zhang 1 , Peng Liu 2 , Ling Liu 1 , Daming Li 3 , Yajie Liu 1 1 Peking University Shenzhen Hospital, Department of Radiation Oncology, Shenzhen, China. 2 Peking University Shenzhen Hospital, Department of Research and Teaching, Shenzhen, China. 3 Affiliated Nanhua Hospital ， University of South China, Department of Radiation Oncology, Hengyang, China

Purpose/Objective:

To analyze the difference in the setup error, setup time, irradiated small bowel volume and mean dose of small intestine in the volumetric modulated arc therapy for cervical cancer using the Vac-lok and the Klarity bellyboard.

Material/Methods:

A total of 36 cervical cancer patients with undergoing volumetric modulated arc therapy in the Department of Radiation Oncology of Peking University Shenzhen Hospital were selected from April 2020 to December 2021. All the patients underwent radical surgery. 18 of them were fixed with a supine Vac-Lok （ Vac-Lok group ）， and the other 18 patients were fixed with a Klarity bellyboard （ bellyboard group ） in prone position. All Patients were taken a daily cone beam CT （ CBCT ） scan before treatment. The acquired images were compared with the CT simulator images, and the setup error, setup time, irradiated small-bowel-volume (SB-V), and mean dose of small intestine (Dmean) were recorded.

Results:

1. Setup error

Each group collected 486 sets of CBCT images. The setup error of lateral (Lat), longitudinal (Lng) and vertical (Vrt) direction of Vac-lok group were (3.2±3.4) mm, (3.4±3.7) mm and (2.4±2.3) mm, respectively, and the rotation error was (0.81˚±0.77˚). In the bellyboard group, the setup errors in Lat, Lng and Vrt directions were (2.7±2.6) mm, (11.3±13.5)mm and (2.7±3.6) mm, respectively, and the rotation error was （ 0.88˚±0.87˚ ） . The setup error of Vac lok group in Lng direction was significantly lower than bellyboard group ， and the setup error of bellyboard group in Lat direction was significantly lower than Vac-lok group (P ＜ 0.05). There was no significant difference in Vrt direction and rotation between the two groups (P ＞ 0.05). （ Table1 ）

2. Setup time