Retrospective dose reconstruction of prostate stereotactic body radiotherapy using cone-beam CT and a log file during VMAT delivery with flattening-filter-free mode

• Published in: Radiological physics and technology Vol. 13; no. 3; pp. 238 - 248
• Main Authors: Imae, Toshikazu, Haga, Akihiro, Watanabe, Yuichi, Takenaka, Shigeharu, Shiraki, Takashi, Nawa, Kanabu, Ogita, Mami, Takahashi, Wataru, Yamashita, Hideomi, Nakagawa, Keiichi, Abe, Osamu
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01-09-2020; Springer Nature B.V
• Subjects: Algorithms; Computed tomography; Deformation; Fields (mathematics); Flattening; Formability; Image acquisition; Image reconstruction; Image registration; Imaging; Mathematical analysis; Medical and Radiation Physics; Medical imaging; Medicine; Medicine & Public Health; Nuclear Medicine; Prostate cancer; Radiation therapy; Radiology; Radiotherapy; Stereotactic body radiotherapy (SBRT); Volumetric-modulated arc therapy (VMAT); Flattening-filter-free (FFF); Log file; Cone-beam computed tomography (CBCT); Dose reconstruction
• ISSN: 1865-0333; 1865-0341
• DOI: 10.1007/s12194-020-00574-3

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 D
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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 Pinnacle
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v9.10 by converting the log file data to Pinnacle
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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.