title: Slice Encoding for Metal Artefact Correction in magnetic resonance imaging examinations for radiotherapy planning.
abstract: Magnetic resonance (MR) and computed tomography (CT) images are degraded in the presence of metallic implants. We investigate whether SEMAC (Slice Encoding for Metal Artifact Correction) MR is advantageous for radiotherapy (RT) planning.
  
  
  
  Conventional and SEMAC MR protocols were compared (1.5T). A spine fixation device suspended in gelatine, two patients with spine fixation devices and six patients with bilateral hip replacements were scanned with both conventional and SEMAC protocols. In spine patients the visibility of the spinal canal and spinal cord was assessed; in prostate patients, the visibility of the prostate, pelvic structures and the pelvic girdle.
  
  
  
  The signal loss volume surrounding the spine fixation device was reduced by approximately 20% when the SEMAC protocol was employed, and registration errors were reduced. For spine patients, the spinal canal was completely visible only using the SEMAC protocol. In hip replacement patients, metal artifacts were local; the signal loss extended to the internal surface of the acetabulum in eight implants with conventional protocols, but only in four using SEMAC.
  
  
  
  SEMAC MR contributes towards correct co-registration of MR and CT images for RT planning, and is particularly relevant when the TV or OARs are close to implants.
authors.affiliation: The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, CR-UK & EPSRC Cancer Imaging Centre, Sutton, United Kingdom. Electronic address: maria.schmidt@icr.ac.uk.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Schmidt
authors.affiliation: The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, CR-UK & EPSRC Cancer Imaging Centre, Sutton, United Kingdom.
authors.forename: Rafal
authors.initials: R
authors.lastname: Panek
authors.affiliation: Royal Marsden NHS Foundation Trust, Radiotherapy Department, Sutton, United Kingdom.
authors.forename: Ruth
authors.initials: R
authors.lastname: Colgan
authors.affiliation: Royal Marsden NHS Foundation Trust, Radiology Department, Sutton, United Kingdom.
authors.forename: Julie
authors.initials: J
authors.lastname: Hughes
authors.affiliation: Royal Marsden NHS Foundation Trust, Radiology Department, Sutton, United Kingdom.
authors.forename: Aslam
authors.initials: A
authors.lastname: Sohaib
authors.affiliation: Royal Marsden NHS Foundation Trust, Neuro-Oncology Unit, Sutton, United Kingdom.
authors.forename: Frank
authors.initials: F
authors.lastname: Saran
authors.affiliation: Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Radiotherapy and Imaging Department, Sutton, United Kingdom.
authors.forename: Julia
authors.initials: J
authors.lastname: Murray
authors.affiliation: St George's Hospital NHS Trust, Orthopaedic Surgery, London, United Kingdom.
authors.forename: Jason
authors.initials: J
authors.lastname: Bernard
authors.affiliation: Siemens Healthcare GmbH, Diagnostic Imaging, Camberley, United Kingdom.
authors.forename: Patrick
authors.initials: P
authors.lastname: Revell
authors.affiliation: Siemens Healthcare Limited, Diagnostic Imaging, Erlangen, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Nittka
authors.affiliation: The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, CR-UK & EPSRC Cancer Imaging Centre, Sutton, United Kingdom.
authors.forename: Martin O
authors.initials: MO
authors.lastname: Leach
authors.affiliation: Royal Marsden NHS Foundation Trust, Radiotherapy Department, Sutton, United Kingdom.
authors.forename: Vibeke N
authors.initials: VN
authors.lastname: Hansen
mesh_terms: D016477:Artifacts; D005593:Fracture Fixation, Internal / Q000295:instrumentation; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008670:Metals; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D019736:Prostheses and Implants; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D013131:Spine / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed
chemical_list: D008670:Metals
keywords: Image fusion for radiotherapy planning; MRI; Metallic implants in radiotherapy