title: Evaluation of the field-in-field technique with lung blocks for breast tangential radiotherapy.
abstract: Several studies have reported the advantages of the field-in-field (FIF) technique in breast radiotherapy, including dose reduction in the lungs by using lung field blocks. We evaluated the FIF technique with lung blocks for breast tangential radiotherapy. Sixteen patients underwent free breathing (FB) computed tomography (CT), followed by two CT procedures performed during breath hold after light inhalation (IN) and light exhalation (EX). Three radiotherapy plans were created using the FIF technique based on the FB-CT images: one without lung blocks (LB0) and two with lung blocks whose monitor units (MUs) were 5 (LB5) and 10 (LB10), respectively. These plans were copied to the IN-CT and EX-CT images. V20Gy, V30Gy, and V40Gy of the ipsilateral lung and V100%, V95%, and the mean dose (Dmean) to the planning target volume (PTV) were analyzed. The extent of changes in these parameters on the IN-plan and EX-plan compared with the FB-plan was evaluated. V20Gy, V30Gy, and V40Gy were significantly smaller for FB-LB5 and FB-LB10 than for FB-LB0; similar results were obtained for the IN-plan and EX-plan. V100%, V95%, and Dmean were also significant smaller for FB-LB5 and FB-LB10 than for FB-LB0. The extent of changes in V20Gy, V30Gy, and V40Gy on the IN-plan and EX-plan compared with the FB-plan was not statistically significant. Lung blocks were useful for dose reduction in the lung and a simultaneous PTV decrease. This technique should not be applied in the general population.
authors.affiliation: Department of Radiology, Gifu University Graduate School of Medicine, Gifu, Japan ; Department of Radiology, Gifu University Hospital, Gifu, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Depertment of Radiation Oncology, Gifu Prefectural Tajimi Hospital, Tajimi, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Hayashi
authors.affiliation: Department of Radiology, Gifu University Graduate School of Medicine, Gifu, Japan ; Department of Radiology, Gifu University Hospital, Gifu, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kajiura
authors.affiliation: Department of Radiology, Gifu University Hospital, Gifu, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Kitahara
authors.affiliation: Department of Radiology, Gifu University Hospital, Gifu, Japan.
authors.forename: Katsuya
authors.initials: K
authors.lastname: Matsuyama
authors.affiliation: Department of Radiology, Gifu University Graduate School of Medicine, Gifu, Japan ; Department of Radiology, Gifu University Hospital, Gifu, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kanematsu
authors.affiliation: Department of Radiology, Gifu University Graduate School of Medicine, Gifu, Japan ; Department of Radiology, Gifu University Hospital, Gifu, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hoshi
keywords: breast cancer; breast radiotherapy; breast-conserving surgery; field-in-field technique; lung blocks