title: X-ray volumetric imaging in image-guided radiotherapy: the new standard in on-treatment imaging.
abstract: OBJECTIVE
  X-ray volumetric imaging (XVI) for the first time allows for the on-treatment acquisition of three-dimensional (3D) kV cone beam computed tomography (CT) images. Clinical imaging using the Synergy System (Elekta, Crawley, UK) commenced in July 2003. This study evaluated image quality and dose delivered and assessed clinical utility for treatment verification at a range of anatomic sites.
  
  
  METHODS
  Single XVIs were acquired from 30 patients undergoing radiotherapy for tumors at 10 different anatomic sites. Patients were imaged in their setup position. Radiation doses received were measured using TLDs on the skin surface. The utility of XVI in verifying target volume coverage was qualitatively assessed by experienced clinicians.
  
  
  RESULTS
  X-ray volumetric imaging acquisition was completed in the treatment position at all anatomic sites. At sites where a full gantry rotation was not possible, XVIs were reconstructed from projection images acquired from partial rotations. Soft-tissue definition of organ boundaries allowed direct assessment of 3D target volume coverage at all sites. Individual image quality depended on both imaging parameters and patient characteristics. Radiation dose ranged from 0.003 Gy in the head to 0.03 Gy in the pelvis.
  
  
  CONCLUSIONS
  On-treatment XVI provided 3D verification images with soft-tissue definition at all anatomic sites at acceptably low radiation doses. This technology sets a new standard in treatment verification and will facilitate novel adaptive radiotherapy techniques.
authors.affiliation: Academic Department of Radiation Oncology, Christie Hospital NHS Trust, Manchester, England, United Kingdom. catherine.mcbain@christie-tr.nwest.nhs.uk
authors.forename: Catherine A
authors.initials: CA
authors.lastname: McBain
authors.forename: Ann M
authors.initials: AM
authors.lastname: Henry
authors.forename: Jonathan
authors.initials: J
authors.lastname: Sykes
authors.forename: Ali
authors.initials: A
authors.lastname: Amer
authors.forename: Tom
authors.initials: T
authors.lastname: Marchant
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Moore
authors.forename: Julie
authors.initials: J
authors.lastname: Davies
authors.forename: Julia
authors.initials: J
authors.lastname: Stratford
authors.forename: Claire
authors.initials: C
authors.lastname: McCarthy
authors.forename: Bridget
authors.initials: B
authors.lastname: Porritt
authors.forename: Peter
authors.initials: P
authors.lastname: Williams
authors.forename: Vincent S
authors.initials: VS
authors.lastname: Khoo
authors.forename: Pat
authors.initials: P
authors.lastname: Price
mesh_terms: D000008:Abdominal Neoplasms / Q000000981:diagnostic imaging; D016543:Central Nervous System Neoplasms / Q000000981:diagnostic imaging; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D010386:Pelvic Neoplasms / Q000000981:diagnostic imaging; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D013899:Thoracic Neoplasms / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods* / Q000592:standards