title: A feasibility study of a hybrid breast-immobilization system for early breast cancer in proton beam therapy.
abstract: OBJECTIVE
  We aimed to develop a new breast-immobilizing system for proton beam therapy (PBT) of early breast cancer (EBC) that would provide the optimum breast shape during the treatment as well as increased fixation reliability by reducing the influence of respiratory movement.
  
  
  METHODS
  The breast-immobilizing system (HyBIS; hybrid breast-immobilizing system) consists of a whole body immobilization system (WBIS), position-converting device (to change patient position), photo-scanning system, breast cup (made using a three-dimensional printer), breast cup-fitting apparatus, breast cup-holding device (to ensure the breast remains lifted in the supine position), and dedicated stretcher fixed to the WBIS (to carry the patient). We conducted a phantom experiment to evaluate the effect of the HyBIS on breast immobilization during the respiratory cycle. Thirteen markers were embedded in the right breast of a female phantom that simulated respiratory thoracic movement at an amplitude of 15 mm, and their displacements on four-dimensional computed tomography were compared between conditions with and without immobilization by HyBIS.
  
  
  RESULTS
  When immobilization was applied with the HyBIS, breast protrusion was maintained in the phantom in the supine treatment position. The mean values of the anteroposterior, superoinferior, lateral, and three-dimensional (3D) displacement of the markers were 2.7 ± 1.7, 0.3 ± 0.5, 0.9 ± 0.8, and 3.1 ± 1.6 mm with HyBIS, and 5.5 ± 2.9, 0.6 ± 0.8, 0.5 ± 0.4, and 5.6 ± 2.9 mm without HyBIS, respectively; thus, the anteroposterior (P = 0.014) and 3D (P = 0.007) displacements significantly improved with HyBIS.
  
  
  CONCLUSIONS
  We demonstrated that the HyBIS can help retain the protruded breast shape in the supine position during treatment and can reduce the influence of respiratory movement. Thus, the HyBIS can help to reliably and precisely perform PBT for EBC.
authors.affiliation: Medipolis Proton Therapy and Research Center, Ibusuki, Japan.|Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Arimura
authors.affiliation: Medipolis Proton Therapy and Research Center, Ibusuki, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ogino
authors.affiliation: Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yoshiura
authors.affiliation: Medipolis Proton Therapy and Research Center, Ibusuki, Japan.
authors.forename: Mitsugi
authors.initials: M
authors.lastname: Matsuyama
authors.affiliation: Medipolis Proton Therapy and Research Center, Ibusuki, Japan.
authors.forename: Naoaki
authors.initials: N
authors.lastname: Kondo
authors.affiliation: Fujidenolo Co., Ltd., Komaki, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Miyazaki
authors.affiliation: Fujidenolo Co., Ltd., Komaki, Japan.
authors.forename: Akari
authors.initials: A
authors.lastname: Sakuragi
authors.affiliation: Kyotokagaku Co., Ltd., Kyoto, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ohara
authors.affiliation: Department of Radiology, Kurume University School of Medicine, Kurume, Japan.
authors.forename: Etsuyo
authors.initials: E
authors.lastname: Ogo
authors.affiliation: Medipolis Proton Therapy and Research Center, Ibusuki, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hishikawa
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007103:Immobilization / Q000295:instrumentation*; D009068:Movement; D056888:Patient Positioning; D061766:Proton Therapy / Q000295:instrumentation*; D012119:Respiration
keywords: breast-immobilization system; early breast cancer; hybrid; phantom; proton beam therapy