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Abstract
With the increasing use of flattening filter free (FFF) beams, it is important to evaluate the impact on the skin dose and target coverage of breast cancer treatments. This study aimed to compare skin doses of treatments using FFF and flattening filter (FF) beams for breast cancer. The study established treatment plans for left breast of an anthropomorphic phantom using Halcyon's 6-MV FFF beam and TrueBeam's 6-MV FF beam. Volumetric modulated arc therapy (VMAT) with varying numbers of arcs and intensity modulated radiation therapy (IMRT) were employed, and skin doses were measured at five points using Gafchromic EBT3 film. Each measurement was repeated three times, and averaged to reduce uncertainty. All plans were compared in terms of plan quality to ensure homogeneous target coverage. The study found that when using VMAT with two, four, and six arcs, in-field doses were 19%, 15%, and 6% higher, respectively, when using Halcyon compared to TrueBeam. Additionally, when using two arcs for VMAT, in-field doses were 10% and 15% higher compared to four and six arcs when using Halcyon. Finally, in-field dose from Halcyon using IMRT was about 1% higher than when using TrueBeam. Our research confirmed that when treating breast cancer with FFF beams, skin dose is higher than with traditional FF beams. Moreover, number of arcs used in VMAT treatment with FFF beams affects skin dose to the patient. To maintain a skin dose similar to that of FF beams when using Halcyon, it may be worth considering increasing the number of arcs.

Affiliations

Jae Hyun Seok 1 2, So Hyun Ahn # 3 4, Woo Sang Ahn # 5, Dong Hyeok Choi 2 6, Seong Soo Shin 7, Wonsik Choi 7, In-Hye Jung 7, Rena Lee 8 9, Jin Sung Kim 2 10
1Department of Integrative Medicine, Yonsei University College of Medicine, Seoul, Korea.
2Medical Physics and Biomedical Engineering Lab (MPBEL), Yonsei University College of Medicine, Seoul, Korea.
3Ewha Medical Research Institute, Ewha Womans University College of Medicine, Seoul, Korea. mpsohyun@gmail.com.
4Ewha Medical Artifical Intelligence Research Institute, Ewha Womans University College of Medicine, Seoul, Korea. mpsohyun@gmail.com.
5Department of Radiation Oncology, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea. anidol@ulsan.ac.kr.
6Department of Medicine, Yonsei University College of Medicine, Seoul, Korea.
7Department of Radiation Oncology, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea.
8Department of Biomedical Engineering, Ewha Womans University, Seoul, Korea.
9Ewha Medical Artifical Intelligence Research Institute, Ewha Womans University College of Medicine, Seoul, Korea.
10Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Korea.
#Contributed equally.