title: Multimodality imaging with CT, MR and FDG-PET for radiotherapy target volume delineation in oropharyngeal squamous cell carcinoma.
abstract: BACKGROUND
  This study aimed to quantify the variation in oropharyngeal squamous cell carcinoma gross tumour volume (GTV) delineation between CT, MR and FDG PET-CT imaging.
  
  
  METHODS
  A prospective, single centre, pilot study was undertaken where 11 patients with locally advanced oropharyngeal cancers (2 tonsil, 9 base of tongue primaries) underwent pre-treatment, contrast enhanced, FDG PET-CT and MR imaging, all performed in a radiotherapy treatment mask. CT, MR and CT-MR GTVs were contoured by 5 clinicians (2 radiologists and 3 radiation oncologists). A semi-automated segmentation algorithm was used to contour PET GTVs. Volume and positional analyses were undertaken, accounting for inter-observer variation, using linear mixed effects models and contour comparison metrics respectively.
  
  
  RESULTS
  Significant differences in mean GTV volume were found between CT (11.9 cm(3)) and CT-MR (14.1 cm(3)), p < 0.006, CT-MR and PET (9.5 cm(3)), p < 0.0009, and MR (12.7 cm(3)) and PET, p < 0.016. Substantial differences in GTV position were found between all modalities with the exception of CT-MR and MR GTVs. A mean of 64 %, 74 % and 77 % of the PET GTVs were included within the CT, MR and CT-MR GTVs respectively. A mean of 57 % of the MR GTVs were included within the CT GTV; conversely a mean of 63 % of the CT GTVs were included within the MR GTV. CT inter-observer variability was found to be significantly higher in terms of position and/or volume than both MR and CT-MR (p < 0.05). Significant differences in GTV volume were found between GTV volumes delineated by radiologists (9.7 cm(3)) and oncologists (14.6 cm(3)) for all modalities (p = 0.001).
  
  
  CONCLUSIONS
  The use of different imaging modalities produced significantly different GTVs, with no single imaging technique encompassing all potential GTV regions. The use of MR reduced inter-observer variability. These data suggest delineation based on multimodality imaging has the potential to improve accuracy of GTV definition.
  
  
  BACKGROUND
  ISRCTN Registry: ISRCTN34165059 . Registered 2nd February 2015.
authors.affiliation: Department of Radiotherapy Physics, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. david.bird3@nhs.net.
authors.forename: David
authors.initials: D
authors.lastname: Bird
authors.affiliation: Department of Nuclear Medicine, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. a.scarsbrook@nhs.net.|Department of Clinical Radiology, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. a.scarsbrook@nhs.net.
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Scarsbrook
authors.affiliation: Department of Radiotherapy Physics, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. sykesjonr@googlemail.com.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Sykes
authors.affiliation: Department of Clinical Oncology, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Beckett Street, LS9 7TF, Leeds, UK. van.ramasamy@gmail.com.
authors.forename: Satiavani
authors.initials: S
authors.lastname: Ramasamy
authors.affiliation: Department of Nuclear Medicine, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. manil.subesinghe@gmail.com.|Department of Clinical Radiology, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. manil.subesinghe@gmail.com.
authors.forename: Manil
authors.initials: M
authors.lastname: Subesinghe
authors.affiliation: Department of Clinical Radiology, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. Brendan.carey@nhs.net.
authors.forename: Brendan
authors.initials: B
authors.lastname: Carey
authors.affiliation: Department of Medical Physics, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. djw@medphysics.leeds.ac.uk.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Wilson
authors.affiliation: Department of Radiotherapy, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. neil.roberts7@nhs.net.
authors.forename: Neil
authors.initials: N
authors.lastname: Roberts
authors.affiliation: Department of Medical Physics, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. garry.mcdermott@nhs.net.
authors.forename: Gary
authors.initials: G
authors.lastname: McDermott
authors.affiliation: Department of Clinical Oncology, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Beckett Street, LS9 7TF, Leeds, UK. ebruzey2007@gmail.com.
authors.forename: Ebru
authors.initials: E
authors.lastname: Karakaya
authors.affiliation: Department of Clinical Oncology, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Beckett Street, LS9 7TF, Leeds, UK. evrim.bayman@hotmail.com.
authors.forename: Evrim
authors.initials: E
authors.lastname: Bayman
authors.affiliation: Department of Clinical Oncology, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Beckett Street, LS9 7TF, Leeds, UK. Mehmet.sen@nhs.net.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Sen
authors.affiliation: Department of Radiotherapy Physics, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. Richard.speight@nhs.net.
authors.forename: Richard
authors.initials: R
authors.lastname: Speight
authors.affiliation: Department of Clinical Oncology, St. James' University Hospital, Leeds Teaching Hospitals NHS Trust, Beckett Street, LS9 7TF, Leeds, UK. Robin.Prestwich@nhs.net.
authors.forename: Robin J D
authors.initials: RJ
authors.lastname: Prestwich
mesh_terms: D000328:Adult; D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000737:chemistry; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009959:Oropharyngeal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D049268:Positron-Emission Tomography / Q000379:methods*; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18