title: Usefulness of the dual energy field-in-field technique in breast tangential radiotherapy.
abstract: OBJECTIVE
  In the field-in-field (FIF) technique in breast tangential radiotherapy, the energy of the subfield is usually the same as the energy of the main field. However, some studies have applied 10-18 MV to subfields in patients with large breasts. We compared two FIF plans in 66 breast cancer patients: in one, the energy of the subfield was the same as that of the main field (the mono energy plan); in the other, it was higher (the dual energy plan).
  
  
  METHODS
  The photon energy of the subfield was 6 MV in the mono energy plan and 10 MV in the dual energy plan. The percentage of the planning target volume (PTV) receiving at least 105, 100, and 95% of the prescribed dose (V105, V100, and V95, respectively) was calculated, as were the maximum and mean doses delivered to the PTV (Dmax and Dmean, respectively). Clinical target volumes (CTVs) and the thickness of the breast between the chest wall and skin surface at the level of the nipple were measured.
  
  
  RESULTS
  V95% was significantly higher in the dual energy plan than in the mono energy plan in patients with CTVs or breast thickness in the highest quartile. There were no significant differences in the other parameters of the two plans in these patients.
  
  
  CONCLUSIONS
  These findings demonstrate the usefulness of the dual energy FIF technique in patients with large breasts receiving breast tangential radiotherapy.
authors.affiliation: Department of Radiology, Gifu University Hospital, Yanagido 1-1, Gifu, 501-1194, Japan. htanaka-gif@umin.ac.jp.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Department of Radiology, Gifu University Hospital, Yanagido 1-1, Gifu, 501-1194, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kajiura
authors.affiliation: Division of Radiation Oncology, Gifu University Hospital, Yanagido 1-1, Gifu, 501-1194, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Kitahara
authors.affiliation: Division of Radiation Oncology, Gifu University Hospital, Yanagido 1-1, Gifu, 501-1194, Japan.
authors.forename: Katsuya
authors.initials: K
authors.lastname: Matsuyama
authors.affiliation: Department of Radiology, Gifu University Hospital, Yanagido 1-1, Gifu, 501-1194, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Kawaguchi
authors.affiliation: Department of Radiology, Gifu University Hospital, Yanagido 1-1, Gifu, 501-1194, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: Department of Radiology, Gifu University Hospital, Yanagido 1-1, Gifu, 501-1194, Japan.
authors.forename: Sunaho
authors.initials: S
authors.lastname: Okada
authors.affiliation: Department of Radiology, Gifu University Hospital, Yanagido 1-1, Gifu, 501-1194, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kanematsu
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011878:Radiotherapy / Q000379:methods
keywords: Breast cancer; Breast radiotherapy; Breast-conserving surgery; Field-in-field technique; Tangential radiotherapy