Study on Optimal Postural Immobilization Method of OSMS in Clinical Application of
Postoperative Radiotherapy for Breast Cancer
LI Junyu1，DU Yi1，ZHOU Shun1，WU Hao1，YANG Jingxian1，YU Songmao1，LI Tingting2，LIU Weiwei1，YUE Haizhen1
1. Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology,
Peking University Cancer Hospital & Institute, Beijing 100142, China丨 2. The Fifth Medical Center, PLA General Hospital, Beijing
100039, China
Abstract：Objective In the application of optical surface monitoring system (OSMS) in postoperative radiotherapy for breast
cancer, the optimal postural immobilization method is determined by comparing the setup error of cone beam CT (CBCT) and
the consistency of OSMS relative to CBCT under the conditions of vacuum pad fixation and neck and thorax thermoplastic mask
fixation. Methods The data of 52 breast cancer patients who were placed by the OSMS system were retrospectively analyzed,
including vacuum pad fixation group (group A, n=24) and neck and thorax thermoplastic mask fixation group (group B, n=28). The
registration error between CBCT and CT was recorded as setup error, and the difference between six-dimensional registration error
obtained by OSMS and CBCT registration result was used to quantify the consistency of setup after absolutization. The difference
and cumulative distribution of setup error and position consistency of the two fixed modes were compared. Results Except for the z
direction, the setup error in group A was better than group B, and there was significant difference between x and z direction (P<0.05).
Except for the z direction, the consistency of setup was better in group A than in group B, and there was significant difference in x, y,
z, Pitch and Roll direction (P<0.05). Except for the cumulative distribution of the setup error in the z direction, group A was basically
better than group B, and there was a significant difference in the z direction (P<0.05). Except for the z direction, the consistent
cumulative distribution of setup in group A was better than group B, and there were significant differences in x, y, Rtn, Pitch, and
Roll directions (P<0.05). The consistent cumulative distribution of six-dimensional setup in group A was better than group B (P<0.05).
Conclusion Two immobilization techniques of OSMS setup can meet the clinical requirements in postoperative radiotherapy for
breast cancer patients. Compared with OSMS setup neck and thorax thermoplastic mask fixation, the setup consistency of OSMS
setup vacuum pad fixation is better than the former, which reduces the setup error to a certain extent, and can be used real-time
monitoring in treatment and bring benefit to patients, so it should be used in priority.
李俊禹1，杜乙1，周舜1，吴昊1，杨敬贤1，于松茂1，李廷廷2，刘巍巍1，岳海振1. OSMS在乳腺癌术后放疗临床应用中体位固定方式优选研究[J]. 中国医疗设备, 2021, 36(4): 45-52.
LI Junyu1，DU Yi1，ZHOU Shun1，WU Hao1，YANG Jingxian1，YU Songmao1，LI Tingting2，LIU Weiwei1，YUE Haizhen1. Study on Optimal Postural Immobilization Method of OSMS in Clinical Application of
Postoperative Radiotherapy for Breast Cancer. China Medical Devices, 2021, 36(4): 45-52.
