title: Evaluation of the Flash effect in breast irradiation using TomoDirect: an investigational study.
abstract: Flash is a specified function in TomoDirect that enables beam expansion by opening additional leaves to the target. This study assessed the theoretical dose distribution resulting from Flash in breast irradiation using TomoDirect. A cylindrical phantom that enabled dose distribution of the breast was used for verifying the effect of planning target volume (PTV) contouring and Flash. A total of 18 Gy in 10 fractions were prescribed to the PTV. Five PTVs were then created by Contracting this contour by 0, 1, 2, 3, 4 and 5 mm, giving PTV-x. Flash ±x is defined by opening x (number) of the leaves. The Flash effect in the air was compared with each set-up error of 5, 10 and 15 mm, respectively. The minimum PTV dose from PTV-1 to PTV-3 increased from 13.88 Gy to 15.86 Gy. In contrast, Dmin in PTV-4 and PTV-5 was 17.80 Gy in 98.88% of the prescription dose. Without Flash, when 5-, 10- and 15-mm set-up errors applied in the PTV, relative doses of 87.88, 23.73 and 7.94% were observed, respectively. However, in Flash 3, which was equal to the usual air margin of 1.875 cm, a relative dose of 104.24% ± 0.30% was observed, irrespective of set-up errors (5 mm to 15 mm). Flash opening is useful for countervailing set-up errors in breast cancer patients who receive breast irradiation with TomoDirect.
authors: Department of Radiation Oncology, St Vincent's Hospital, the Catholic University of Korea, 93, Ji-dong, Paldal-gu, Suwon, Gyeonggi-do, Korea Department of Biomedical Engineering, Electronic Engineering, Jeju National University of Korea, Jeju-si, Jeju Special Self-Governing Province, Korea.
authors: Dae Gyu
authors: DG
authors: Kang
authors: Department of Medical Physics, Kyong-gi University of Korea, Yeongtong-gu, Suwon, Gyeonggi-do, Korea.
authors: Sung Ill
authors: SI
authors: Park
authors: Department of Radiation Oncology, St Vincent's Hospital, the Catholic University of Korea, 93, Ji-dong, Paldal-gu, Suwon, Gyeonggi-do, Korea.
authors: Sung Hwan
authors: SH
authors: Kim
authors: Department of Radiation Oncology, St Vincent's Hospital, the Catholic University of Korea, 93, Ji-dong, Paldal-gu, Suwon, Gyeonggi-do, Korea.
authors: Mi Joo
authors: MJ
authors: Chung
authors: Department of Biomedical Engineering, Electronic Engineering, Jeju National University of Korea, Jeju-si, Jeju Special Self-Governing Province, Korea.
authors: Kwang-Man
authors: KM
authors: Lee
authors: Department of Radiation Oncology, St Vincent's Hospital, the Catholic University of Korea, 93, Ji-dong, Paldal-gu, Suwon, Gyeonggi-do, Korea koppul@catholic.ac.kr.
authors: Jong Hoon
authors: JH
authors: Lee
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008954:Models, Biological; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation* / Q000379:methods; D016896:Treatment Outcome
keywords: Flash effect; TomoDirect; radiation therapy; set-up