title: Radiation treatment planning with an integrated positron emission and computer tomography (PET/CT): a feasibility study.
abstract: OBJECTIVE
  To investigate the usefulness of hardware coregistered PET/CT images for target volume definition.
  
  
  METHODS
  Thirty-nine patients presenting with various solid tumors were investigated. CT and a FDG-PET were obtained in treatment position in an integrated PET/CT scanner, and coregistered images were used for treatment planning. First, volume delineation was performed on the CT data. In a second step, the corresponding PET data were used as an overlay to the CT data to define the target volume. Delineation was done independently by two investigators.
  
  
  RESULTS
  Coregistered PET/CT showed good fusion accuracy. The GTV increased by 25% or more because of PET in 17% of cases with head-and-neck (2/12) and lung cancer (1/6), and in 33% (7/21) in cancer of the pelvis. The GTV was reduced > or =25% in 33% of patients with head-and-neck cancer (4/12), in 67% with lung cancer (4/6), and 19% with cancer of the pelvis (4/21). Overall, in 56% (22/39) of cases, GTV delineation was changed significantly if information from metabolic imaging was used in the planning process. The modification of the GTV translated into altered PTV changes exceeding >20% in 46% (18/39) of cases. With PET, volume delineation variability between two independent oncologists decreased from a mean volume difference of 25.7 cm(3) to 9.2 cm(3) associated with a reduction of the standard deviation from 38.3 cm(3) to 13.3 cm(3) (p = 0.02). In 16% of cases, PET/CT revealed distant metastasies, changing the treatment strategy from curative to palliative.
  
  
  CONCLUSIONS
  Integrated PET/CT for treatment planning for three-dimensional conformal radiation therapy improves the standardization of volume delineation compared with that of CT alone. PET/CT has the potential for reducing the risk for geographic misses, to minimize the dose of ionizing radiation applied to non-target organs, and to change the current practice to three-dimensional conformal radiation therapy planning by taking into account the metabolic and biologic features of cancer. The impact on treatment outcome remains to be demonstrated.
authors.affiliation: Department of Radiation Oncology Zurich University Hospital, Zurich, Switzerland. ciernik@usz.ch
authors.forename: I Frank
authors.initials: IF
authors.lastname: Ciernik
authors.forename: Elena
authors.initials: E
authors.lastname: Dizendorf
authors.forename: Brigitta G
authors.initials: BG
authors.lastname: Baumert
authors.forename: Beatrice
authors.initials: B
authors.lastname: Reiner
authors.forename: Cyrill
authors.initials: C
authors.lastname: Burger
authors.forename: J Bernard
authors.initials: JB
authors.lastname: Davis
authors.forename: Urs M
authors.initials: UM
authors.lastname: Lütolf
authors.forename: Hans C
authors.initials: HC
authors.lastname: Steinert
authors.forename: Gustav K
authors.initials: GK
authors.lastname: Von Schulthess
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005240:Feasibility Studies; D005260:Female; D005833:Genital Neoplasms, Female / Q000000981:diagnostic imaging / Q000532:radiotherapy; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D015588:Observer Variation; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D014055:Tomography, Emission-Computed / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*