Retrospective dose reconstruction of prostate stereotactic body radiotherapy using cone-beam CT and a log file during VM
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Retrospective dose reconstruction of prostate stereotactic body radiotherapy using cone‑beam CT and a log file during VMAT delivery with flattening‑filter‑free mode Toshikazu Imae1 · Akihiro Haga2 · Yuichi Watanabe3 · Shigeharu Takenaka1 · Takashi Shiraki1 · Kanabu Nawa1 · Mami Ogita1 · Wataru Takahashi1 · Hideomi Yamashita1 · Keiichi Nakagawa1 · Osamu Abe1 Received: 22 July 2019 / Revised: 1 July 2020 / Accepted: 6 July 2020 © Japanese Society of Radiological Technology and Japan Society of Medical Physics 2020
Abstract This study aimed to reconstruct the dose distribution of single fraction of stereotactic body radiotherapy for patients with prostate cancer using cone-beam computed tomography (CBCT) and a log file during volumetric-modulated arc therapy (VMAT) delivery with flattening-filter-free (FFF) mode. Twenty patients with clinically localized prostate cancer were treated with FFF-VMAT, and projection images for in-treatment CBCT (iCBCT) imaging were concomitantly acquired with a log file. A D95 dose of 36.25 Gy in five fractions was prescribed to each planning target volume (PTV) on each treatment planning CT (pCT). Deformed pCT (dCT) was obtained from the iCBCT using a hybrid deformable image registration algorithm. Dose distributions on the dCT were calculated using P innacle3 v9.10 by converting the log file data to P innacle3 data format using an in-house software. Dose warping was performed by referring to deformation vector fields calculated from pCT and dCT. Reconstructed dose distribution was compared with that of the original plan. Dose differences between the original and reconstructed dose distributions were within 3% at the isocenter and observed in PTV and organ-at-risk (OAR) regions. Differences in OAR regions were relatively larger than those in the PTV, presumably because OARs were more deformed than the PTV. Therefore, our method can be used successfully to reconstruct the dose distributions of one fraction using iCBCT and a log file during FFF-VMAT delivery. Keywords Cone-beam computed tomography (CBCT) · Dose reconstruction · Flattening-filter-free (FFF) · Log file · Stereotactic body radiotherapy (SBRT) · Volumetric-modulated arc therapy (VMAT)
* Toshikazu Imae imaet‑[email protected]‑tokyo.ac.jp
Hideomi Yamashita [email protected]
Akihiro Haga haga@tokushima‑u.ac.jp
Keiichi Nakagawa nakagawa‑[email protected]‑tokyo.ac.jp
Yuichi Watanabe [email protected]
Osamu Abe abe‑[email protected]‑tokyo.ac.jp
Shigeharu Takenaka takenakas‑[email protected]‑tokyo.ac.jp
1
Takashi Shiraki shiraki‑[email protected]‑tokyo.ac.jp
Department of Radiology, University of Tokyo Hospital, 3‑7‑1 Hongo, Bunkyo‑ku, Tokyo 113‑8655, Japan
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Graduate School of Biomedical Science, Tokushima University, 3‑18‑15, Kuramoto‑cho, Tokushima 770‑8503, Japan
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Faculty of Health Sciences, Komazawa University, 1‑23‑1Komazawa, Setagaya‑ku, Tokyo 154‑8525, Japan
Kanabu Nawa nawak‑[email protected]‑tokyo.ac.jp Mami Ogita ogitam‑[email protected]‑tokyo.ac.jp Wataru Takahashi takahashiw‑[email protected]‑tokyo.ac.jp
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