title: The application of positron emission tomography/computed tomography in radiation treatment planning: effect on gross target volume definition and treatment management.
abstract: OBJECTIVE
  To analyse the effect of the use of molecular imaging on gross target volume (GTV) definition and treatment management.
  
  
  METHODS
  Fifty patients with various solid tumours who underwent positron emission tomography (PET)/computed tomography (CT) simulation for radiotherapy planning from 2006 to 2008 were enrolled in this study. First, F-18 fluorodeoxyglucose (FDG)-PET and CT scans of the treatment site in the treatment position and then a whole body scan were carried out with a dedicated PET/CT scanner and fused thereafter. FDG-avid primary tumour and lymph nodes were included into the GTV. A multidisciplinary team defined the target volume, and contouring was carried out by a radiation oncologist using visual methods. To compare the PET/CT-based volumes with CT-based volumes, contours were drawn on CT-only data with the help of site-specific radiologists who were blind to the PET/CT results after a median time of 7 months.
  
  
  RESULTS
  In general, our PET/CT volumes were larger than our CT-based volumes. This difference was significant in patients with head and neck cancers. Major changes (> or =25%) in GTV delineation were observed in 44% of patients. In 16% of cases, PET/CT detected incidental second primaries and metastatic disease, changing the treatment strategy from curative to palliative.
  
  
  CONCLUSIONS
  Integrating functional imaging with FDG-PET/CT into the radiotherapy planning process resulted in major changes in a significant proportion of our patients. An interdisciplinary approach between imaging and radiation oncology departments is essential in defining the target volumes.
authors.affiliation: Department of Radiation Oncology, Istanbul Bilim University, School of Medicine, Cemil Aslan Güder sok 8 Gayrettepe, 34340 Istanbul, Turkey. sefikigdem@gmail.com
authors.forename: S
authors.initials: S
authors.lastname: Iğdem
authors.forename: G
authors.initials: G
authors.lastname: Alço
authors.forename: T
authors.initials: T
authors.lastname: Ercan
authors.forename: B
authors.initials: B
authors.lastname: Unalan
authors.forename: B
authors.initials: B
authors.lastname: Kara
authors.forename: G
authors.initials: G
authors.lastname: Geceer
authors.forename: C
authors.initials: C
authors.lastname: Akman
authors.forename: F O
authors.initials: FO
authors.lastname: Zengin
authors.forename: S
authors.initials: S
authors.lastname: Atilla
authors.forename: S
authors.initials: S
authors.lastname: Okkan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008875:Middle Aged; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D049268:Positron-Emission Tomography; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed; D055815:Young Adult