title: Threshold modification for tumour imaging in non-small-cell lung cancer using positron emission tomography.
abstract: OBJECTIVE
  Positron emission tomography (PET) has been used increasingly in the staging and radiotherapy treatment planning of non-small-cell lung cancer (NSCLC). This study investigates the factors that affect the resultant size of a given image on PET.
  
  
  METHODS
  PET was used to assess the geometric characteristics of a series of radioisotope-filled, stationary spheres of known volume, surrounded by positron-emitting radioactive tracer of variable activity. The resultant PET-derived spherical volumes were then referenced to the known spherical volumes in order to illustrate quantitatively the potential influence of image threshold, tumour size and background concentration. This influence was further illustrated by clinical examples.
  
  
  RESULTS
  Considering the diameter of the spheres used in this study (10-48 mm), higher image thresholds were required for accurate rendering of the smallest spherical volumes. This inverse relationship was most consistently illustrated at the lowest background intensity ratios.
  
  
  CONCLUSIONS
  PET-derived volumes of NSCLC must be interpreted with caution. The data presented in this study may be used to guide the selection of appropriate image thresholds for potential clinical application.
authors.affiliation: Department of Radiation Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.
authors.forename: Brian
authors.initials: B
authors.lastname: Yaremko
authors.forename: Terence
authors.initials: T
authors.lastname: Riauka
authors.forename: Donald
authors.initials: D
authors.lastname: Robinson
authors.forename: Brad
authors.initials: B
authors.lastname: Murray
authors.forename: Alexander
authors.initials: A
authors.lastname: McEwan
authors.forename: Wilson
authors.initials: W
authors.lastname: Roa
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis* / Q000473:pathology*; D004867:Equipment Design; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D009367:Neoplasm Staging / Q000379:methods; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000379:methods* / Q000592:standards*; D014057:Tomography, X-Ray Computed / Q000379:methods