4D-CBCT reconstruction using MV portal imaging during volumetric modulated arc therapy |
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Authors: | Satoshi KidaNaoya Saotome Yoshitaka MasutaniHideomi Yamashita Kuni OhtomoKeiichi Nakagawa Akira SakumiAkihiro Haga |
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Institution: | Department of Radiology, University of Tokyo Hospital, Japan |
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Abstract: | BackgroundRecording target motion during treatment is important for verifying the irradiated region. Recently, cone-beam computed tomography (CBCT) reconstruction from portal images acquired during volumetric modulated arc therapy (VMAT), known as VMAT-CBCT, has been investigated. In this study, we developed a four-dimensional (4D) version of the VMAT-CBCT.Materials and methodsThe MV portal images were sequentially acquired from an electronic portal imaging device. The flex, background, monitor unit, field size, and multi-leaf collimator masking corrections were considered during image reconstruction. A 4D VMAT-CBCT requires a respiratory signal during image acquisition. An image-based phase recognition (IBPR) method was performed using normalised cross correlation to extract a respiratory signal from the series of portal images.ResultsOur original IBPR method enabled us to reconstruct 4D VMAT-CBCT with no external devices. We confirmed that 4D VMAT-CBCT was feasible for two patients and in good agreement with in-treatment 4D kV-CBCT.ConclusionThe visibility of the anatomy in 4D VMAT-CBCT reconstruction for lung cancer patients has the potential of using 4D VMAT-CBCT as a tool for verifying relative positions of tumour for each respiratory phase. |
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Keywords: | CBCT 4D-CT Respiratory motion Portal imaging VMAT |
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