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Abstract
Background: This study was conducted to evaluate the efficiency and accuracy of the daily patient setup for breast cancer patients by applying surface-guided radiation therapy (SGRT) using the Halcyon system instead of conventional laser alignment based on the skin marking method.

Methods and materials: We retrospectively investigated 228 treatment fractions using two different initial patient setup methods. The accuracy of the residual rotational error of the SGRT system was evaluated by using an in-house breast phantom. The residual translational error was analyzed using the couch position difference in the vertical, longitudinal, and lateral directions between the reference computed tomography and daily kilo-voltage cone beam computed tomography acquired from the record and verification system. The residual rotational error (pitch, yaw, and roll) was also calculated using an auto rigid registration between the two images based on Velocity. The total setup time, which combined the initial setup time and imaging time, was analyzed to evaluate the efficiency of the daily patient setup for SGRT.

Results: The average residual rotational errors using the in-house fabricated breast phantom for pitch, roll, and yaw were 0.14°, 0.13°, and 0.29°, respectively. The average differences in the couch positions for laser alignment based on the skin marking method were 2.7 ± 1.6 mm, 2.0 ± 1.2 mm, and 2.1 ± 1.0 mm for the vertical, longitudinal, and lateral directions, respectively. For SGRT, the average differences in the couch positions were 1.9 ± 1.2 mm, 2.9 ± 2.1 mm, and 1.9 ± 0.7 mm for the vertical, longitudinal, and lateral directions, respectively. The rotational errors for pitch, yaw, and roll without the surface-guided radiation therapy approach were 0.32 ± 0.30°, 0.51 ± 0.24°, and 0.29 ± 0.22°, respectively. For SGRT, the rotational errors were 0.30 ± 0.22°, 0.51 ± 0.26°, and 0.19 ± 0.13°, respectively. The average total setup times considering both the initial setup time and imaging time were 314 s and 331 s, respectively, with and without SGRT.

Conclusion: We demonstrated that using SGRT improves the accuracy and efficiency of initial patient setups in breast cancer patients using the Halcyon system, which has limitations in correcting the rotational offset.

Affiliations

Seonghee Kang 1 2 3, Hyeongmin Jin 1 2 3, Ji Hyun Chang 1 4, Bum-Sup Jang 1 4, Kyung Hwan Shin 1 4 5, Chang Heon Choi 6 7 8, Jung-In Kim 9 10 11
1Department of Radiation Oncology, Seoul National University Hospital, 101, Daehak-ro, Jongno-gu, Seoul, Republic of Korea.
2Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.
3Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Republic of Korea.
4Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Republic of Korea.
5Cancer Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea.
6Department of Radiation Oncology, Seoul National University Hospital, 101, Daehak-ro, Jongno-gu, Seoul, Republic of Korea. dm140@naver.com.
7Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea. dm140@naver.com.
8Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Republic of Korea. dm140@naver.com.
9Department of Radiation Oncology, Seoul National University Hospital, 101, Daehak-ro, Jongno-gu, Seoul, Republic of Korea. madangin@outlook.com.
10Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea. madangin@outlook.com.
11Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Republic of Korea. madangin@outlook.com.