title: Design and evaluation of electron beam energy degraders for breast boost irradiation.
abstract: BACKGROUND
  For breast cancer patients who require electron boost energies between 6 and 9 MeV, an energy degraders (ED) in the 9 MeV beamline was specially designed and manufactured to increase the skin dose of 6 MeV and to reduce the penetration depth of 9 MeV beams.
  
  
  METHODS
  We used Monte Carlo (MC) techniques as a guide in the design of ED for use with linear accelerators. In order to satisfy percent depth dose (PDD) characteristics and dose profile uniformity in water, the shape and thickness of Lucite® ED in the 9 MeV beamline was iteratively optimized and then manufactured. The ED geometry consists of a truncated cone attached on top of a plane plate, with total central thickness of 1.0 cm. The ED was placed on the lower most scraper of the electron applicator. The PDDs, profiles, and output factors were measured in water to validate the MC-based design.
  
  
  RESULTS
  Skin doses with the EDs increased by 8-9 %, compared to those of the 9 MeV beam. The outputs with the EDs were 0.882 and 0.972 for 10 × 10 and 15 × 15 cm(2) cones, respectively, as compared to that of a conventional 9 MeV beam for a 10 × 10 cm(2) cone. The X-ray contamination remained less than 1.5 %. In-vivo measurements were also performed for three breast boost patients and showed close agreement with expected values.
  
  
  CONCLUSIONS
  The optimally designed ED in the 9 MeV beamline provides breast conserving patients with a new energy option of 7 MeV for boost of the shallow tumor bed. It would be an alternative to bolus and thus eliminate inconvenience and concern about the daily variation of bolus setup.
authors: Department of Transdisciplinary Studies, Program in Biomedical Radiation Sciences, Seoul National University Graduate School of Convergence Science and Technology, Seoul, 151-742, Korea.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.|Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea.
authors: Jong In
authors: JI
authors: Park
authors: Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.|Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.
authors: Sung Whan
authors: SW
authors: Ha
authors: Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.|Advanced Institutes of Convergence Technology, Seoul National University, Suwon, Korea.
authors: Jung-In
authors: JI
authors: Kim
authors: Department of Transdisciplinary Studies, Program in Biomedical Radiation Sciences, Seoul National University Graduate School of Convergence Science and Technology, Seoul, 151-742, Korea.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.
authors: Hyunseok
authors: H
authors: Lee
authors: Department of Transdisciplinary Studies, Program in Biomedical Radiation Sciences, Seoul National University Graduate School of Convergence Science and Technology, Seoul, 151-742, Korea.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.
authors: Jaegi
authors: J
authors: Lee
authors: Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.|Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea.
authors: Il Han
authors: IH
authors: Kim
authors: Department of Transdisciplinary Studies, Program in Biomedical Radiation Sciences, Seoul National University Graduate School of Convergence Science and Technology, Seoul, 151-742, Korea. sye@snu.ac.kr.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea. sye@snu.ac.kr.|Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea. sye@snu.ac.kr.|Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea. sye@snu.ac.kr.|Advanced Institutes of Convergence Technology, Seoul National University, Suwon, Korea. sye@snu.ac.kr.
authors: Sung-Joon
authors: SJ
authors: Ye
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D009010:Monte Carlo Method; D011874:Radiometry / Q000379:methods; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods*
keywords: Breast boost irradiation; Electron energy degrader; Linear accelerator; Monte Carlo simulation