4D-CBCT reconstruction using MV portal imaging during volumetric modulated arc therapy

Satoshi Kida, Naoya Saotome, Yoshitaka Masutani, Hideomi Yamashita, Kuni Ohtomo, Keiichi Nakagawa, Akira Sakumi, Akihiro Haga

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)


Background: Recording 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 methods: The 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. Results: Our 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. Conclusion: The 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.

Original languageEnglish
Pages (from-to)380-385
Number of pages6
JournalRadiotherapy and Oncology
Issue number3
Publication statusPublished - 2011 Sept


  • 4D-CT
  • CBCT
  • Portal imaging
  • Respiratory motion
  • VMAT

ASJC Scopus subject areas

  • Hematology
  • Oncology
  • Radiology Nuclear Medicine and imaging


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