title: CT reconstruction from portal images acquired during volumetric-modulated arc therapy.
abstract: Volumetric-modulated arc therapy (VMAT), a form of intensity-modulated arc therapy (IMAT), has become a topic of research and clinical activity in recent years. As a form of arc therapy, portal images acquired during the treatment fraction form a (partial) Radon transform of the patient. We show that these portal images, when used in a modified global cone-beam filtered backprojection (FBP) algorithm, allow a surprisingly recognizable CT-volume to be reconstructed. The possibility of distinguishing anatomy in such VMAT-CT reconstructions suggests that this could prove to be a valuable treatment position-verification tool. Further, some potential for local-tomography techniques to improve image quality is shown.
authors.affiliation: Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey, SM2 5PT UK. Gavin.Poludniowski@icr.ac.uk
authors.forename: G
authors.initials: G
authors.lastname: Poludniowski
authors.forename: M D R
authors.initials: MD
authors.lastname: Thomas
authors.forename: P M
authors.initials: PM
authors.lastname: Evans
authors.forename: S
authors.initials: S
authors.lastname: Webb
mesh_terms: D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D014057:Tomography, X-Ray Computed / Q000379:methods*