title: Commissioning of a new wide-bore MRI scanner for radiotherapy planning of head and neck cancer.
abstract: OBJECTIVE
  A combination of CT and MRI is recommended for radiotherapy planning of head and neck cancers, and optimal spatial co-registration is achieved by imaging in the treatment position using the necessary immobilisation devices on both occasions, something which requires wide-bore scanners. Quality assurance experiments were carried out to commission a newly installed 1.5-T wide-bore MRI scanner and a dedicated, flexible six-channel phased array head and neck coil.
  
  
  METHODS
  Signal-to-noise ratio (SNR) and spatial signal uniformity were quantified using a homogeneous aqueous phantom, and geometric distortion was quantified using a phantom with water-filled fiducials in a grid pattern. Volunteer scans were also used to determine the in vivo image quality. Clinically relevant T1 weighted and T2 weighted fat-suppressed sequences were assessed in multiple scan planes (both sequences fast spin echo based). The performance of two online signal uniformity correction schemes, one utilising low-resolution reference scans and the other not utilising low-resolution reference scans, was compared.
  
  
  RESULTS
  Geometric distortions, for a ±35-kHz bandwidth, were <1 mm for locations within 10 cm of the isocentre rising to 1.8 mm at 18 cm away. SNR was above 50, and uniformity in the axial plane was 71% and 95% before and after uniformity correction, respectively.
  
  
  CONCLUSIONS
  The combined performance of the wide-bore scanner and the dedicated coil was adjudged adequate, although superior-inferior spatial coverage was slightly limited in the lower neck.
  
  
  CONCLUSIONS
  These results will be of interest to the increasing number of oncology centres that are seeking to incorporate MRI into planning practice using dedicated equipment.
authors.affiliation: Radiation Physics Department, Queen's Centre for Oncology and Haematology, Hull and East Yorkshire Hospitals NHS Trust, Castle Hill Hospital, Cottingham, UK.
authors.forename: G P
authors.initials: GP
authors.lastname: Liney
authors.forename: S C
authors.initials: SC
authors.lastname: Owen
authors.forename: A K E
authors.initials: AK
authors.lastname: Beaumont
authors.forename: V R
authors.initials: VR
authors.lastname: Lazar
authors.forename: D J
authors.initials: DJ
authors.lastname: Manton
authors.forename: A W
authors.initials: AW
authors.lastname: Beavis
mesh_terms: D004867:Equipment Design; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation*; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed