Optimization of immobilization and positioning methods in hypofractionated stereotactic radiotherapy for brain metastases
10.3760/cma.j.cn112271-20230818-00053
- VernacularTitle:脑转移瘤大分割立体定向放射治疗中体位固定设备联合摆位引导方式的优选研究
- Author:
Longxing LI
1
;
Yan GAO
;
Hongtao CHEN
;
Zihuang LI
;
Yabin SHI
Author Information
1. 深圳市人民医院 暨南大学第二临床医学院 南方科技大学第一附属医院肿瘤放疗科，深圳 518020
- Keywords:
Brain metastasis;
Stereotactic radiotherapy;
Optical surface monitoring system (OSMS);
Open face thermoplastic mask;
Setup error
- From:
Chinese Journal of Radiological Medicine and Protection
2024;44(7):587-593
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To compare translational and rotational setup errors between immobilization with open masks combined with positioning with the optical surface monitoring system (OSMS) and immobilization with full masks combined with positioning with laser lights and mask markers, find the advantages of open masks combined with OSMS in hypofractionated stereotactic radiotherapy (HSRT) for brain metastases, and calculate planning target volume (PTV) expansions with different immobilization and positioning method for patients with brain metastases.Methods:The setup data of 55 patients with brain metastases who received HSRT were analyzed retrospectively. According to immobilization and positioning method, the patients were divided into group A (OSMS + open masks), group B1 (full head-neck-shoulders masks + polyurethane foam cushions), and group B2 (full head-neck-shoulders masks + standard headrests). Positioning was directed by automatic couch motion in OSMS in group A and by laser lights and mask markers in groups B1 and B2. Cone beam computed tomography (CBCT) scans were registered using the bone registration method to obtain setup errors in six directions ( x, y, z, roll, pitch, yaw). PTV expansions were calculated according to the van Herk formula. Results:A total of 288 sets of CBCT registration data were acquired. Among three groups, group A showed the smallest mean setup errors and 3D vector error, which were (0.47±0.33) mm, (0.49±0.31) mm, (0.44±0.31) mm, (0.42±0.32)°, (0.48±0.31)°, (0.42±0.22)°, and (0.90±0.39) mm, respectively. Group A differed significantly from group B1 and group B2 in the errors at all directions ( P < 0.05) except for the yaw direction compared with group B1 ( P > 0.05). Group A had no setup error ≥2 mm in translational directions or ≥2° in rotational directions. Group B1 showed significantly smaller setup errors in the y, z, and yaw directions and 3D vector error than group B2 ( P < 0.05). In group A, PTV expansions in three directions ( x, y, and z) were 1.32, 1.19, and 1.22 mm, respectively, which were smaller than those of the other two groups. Conclusions:In HSRT for patient with brain metastases, compared with full head-neck-shoulders masks combined with laser lights and mask markers, open masks combined with OSMS can significantly improve setup precision in six directions and reduce repeated setup and PTV expansions, which shows promise for clinical application.
