title: 4D digitally reconstructed radiography for verifying a lung tumor position during volumetric modulated arc therapy.
abstract: We have proposed four dimensional (4D) digitally reconstructed radiography (DRR) for verifying a lung tumor position during volumetric modulated arc therapy (VMAT). An internal target volume (ITV) was defined based on two clinical target volumes (CTVs) delineated on maximum exhalation and maximum inhalation images acquired by 4D planning computed tomography (CT). A planning target volume (PTV) was defined by adding a margin of 5 mm to the ITV on the maximum exhalation 3D CT images. A single-arc VMAT plan was created on the same CT data using Pinnacle SmartArc with a maximum multi-leaf collimator leaf speed of 1 mm/degree, thereby resulting in quasi-conformal field shapes while optimizing each beam intensity for each gantry angle. During VMAT delivery, cone-beam CT (CBCT) projection data were acquired by an on-board kilovoltage X-ray unit and a flat panel 2D detector. Four CBCT image sets with different respiratory phases were reconstructed using in-house software, where respiratory phases were extracted from the projection data. Subsequently a CTV was delineated on each of the 4D CBCT images by an oncologist. Using the resulting 4D CBCT data including the CTV contours, 4D DRRs during the VMAT delivery were calculated as a function of gantry angle. It was confirmed that the contoured CTV was within the radiation field during the four-fraction lung VMAT delivery. The proposed 4D DRR may facilitate the verification of the position of a respiratory moving lung tumor during VMAT delivery on each treatment day.
authors: Department of Radiology, University of Tokyo Hospital, 7-3-1 Hongo Bunkyo-ku, Tokyo, Japan. k-nak@fg7.so-net.ne.jp
authors: Keiichi
authors: K
authors: Nakagawa
authors: Satoshi
authors: S
authors: Kida
authors: Akihiro
authors: A
authors: Haga
authors: Yoshitaka
authors: Y
authors: Masutani
authors: Hideomi
authors: H
authors: Yamashita
authors: Tsuyoshi
authors: T
authors: Onoe
authors: Toshikazu
authors: T
authors: Imae
authors: Kenichiro
authors: K
authors: Tanaka
authors: Kuni
authors: K
authors: Ohtomo
authors: Kiyoshi
authors: K
authors: Yoda
mesh_terms: D000465:Algorithms; D054893:Cone-Beam Computed Tomography / Q000379:methods; D004307:Dose-Response Relationship, Radiation; D004867:Equipment Design; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008175:Lung Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000379:methods; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D015203:Reproducibility of Results; D014965:X-Rays