title: How few cancer cells can be detected by positron emission tomography? A frequent question addressed by an in vitro study.
abstract: OBJECTIVE
  Positron emission tomography (PET) has gained widespread use in cancer diagnosis and treatment, but how many malignant cells are required for a tumour to be detected by PET?
  
  
  METHODS
  Three human cancer cell lines [glioblastoma and two subtypes of small cell lung cancer (SCLC)] in concentrations from 10(4) to 10(7) were seeded on six-well plates or plastic tubes and treated with [(18)F]fluorodeoxy-glucose (FDG) in vitro. FDG retention was measured in a PET/CT scanner and in a calibrated well counter. The clinical situation was simulated using a cylinder phantom with a background concentration of FDG.
  
  
  RESULTS
  The theoretical detection limit was found to be around 10(5) malignant cells. In a cylinder phantom the detection limit was increased by a factor of 10. The FDG retention by the glioblastoma cell line was significantly higher than the activity of the SCLC cell line. FDG retention measured by PET and a gamma counter was closely correlated to the number of cells and a linear relationship was found.
  
  
  CONCLUSIONS
  The detection limit of PET is in the magnitude of 10(5) to 10(6) malignant cells. The experimental set-up was robust and well suited as a platform for further investigations of factors influencing the detection limit of PET.
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital, Copenhagen, Denmark. malene.fischer@rh.dk
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Fischer
authors.forename: Minna W B
authors.initials: MW
authors.lastname: Olsen
authors.forename: Carsten D
authors.initials: CD
authors.lastname: Ley
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Klausen
authors.forename: Jann
authors.initials: J
authors.lastname: Mortensen
authors.forename: Liselotte
authors.initials: L
authors.lastname: Højgaard
authors.forename: Paul E G
authors.initials: PE
authors.lastname: Kristjansen
mesh_terms: D018288:Carcinoma, Small Cell / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D002452:Cell Count / Q000379:methods; D045744:Cell Line, Tumor; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D005909:Glioblastoma / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D019788:Fluorodeoxyglucose F18