title: Dose reconstruction technique using non-rigid registration to evaluate spatial correspondence between high-dose region and late radiation toxicity: a case of tracheobronchial stenosis after external beam radiotherapy combined with endotracheal brachytherapy for tracheal cancer.
abstract: OBJECTIVE
  Small organ subvolume irradiated by a high-dose has been emphasized to be associated with late complication after radiotherapy. Here, we demonstrate a potential use of surface-based, non-rigid registration to investigate how high-dose volume topographically correlates with the location of late radiation morbidity in a case of tracheobronchial radiation stenosis.
  
  
  METHODS
  An algorithm of point set registration was implemented to handle non-rigid registration between contour points on the organ surfaces. The framework estimated the global correspondence between the dose distribution and the varying anatomical structure. We applied it to an 80-year-old man who developed tracheobronchial stenosis 2 years after high-dose-rate endobronchial brachytherapy (HDR-EBT) (24 Gy in 6 Gy fractions) and external beam radiotherapy (EBRT) (40 Gy in 2 Gy fractions) for early-stage tracheal cancer.
  
  
  CONCLUSIONS
  Based on the transformation function computed by the non-rigid registration, irradiated dose distribution was reconstructed on the surface of post-treatment tracheobronchial stenosis. For expressing the equivalent dose in a fractional dose of 2 Gy in HDR-EBT, α/β of linear quadratic model was assumed as 3 Gy for the tracheal bronchus. The tracheobronchial surface irradiated by more than 100 Gyαβ3 tended to develop severe stenosis, which attributed to a more than 50% decrease in the luminal area. The proposed dose reconstruction technique can be a powerful tool to predict late radiation toxicity with spatial consideration.
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Kazuma
authors.initials: K
authors.lastname: Kobayashi
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Naoya
authors.initials: N
authors.lastname: Murakami
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Koji
authors.initials: K
authors.lastname: Inaba
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Akihisa
authors.initials: A
authors.lastname: Wakita
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Okamoto
authors.affiliation: Department of Thoracic Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Jun
authors.initials: J
authors.lastname: Sato
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Rei
authors.initials: R
authors.lastname: Umezawa
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Kana
authors.initials: K
authors.lastname: Takahashi
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Igaki
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of Radiology, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Shigematsu
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo.
authors.forename: Jun
authors.initials: J
authors.lastname: Itami
keywords: image registration; radiation toxicity; tracheal cancer