title: Assessment of inter- and intrapatient variability in C15O2 positron emission tomography measurements of blood flow in patients with intra-abdominal cancers.
abstract: OBJECTIVE
  The aim of the study was to evaluate the inter- and intrapatient variability of positron emission tomography (PET) measurements of perfusion in advanced solid cancers.
  
  
  METHODS
  Thirty-seven patients with predominantly intra-abdominal tumors underwent PET imaging using inhaled C15O2. Repeat data were obtained by scanning five patients twice, 1 week apart, with no intervening therapy. Regional flow and the volume of distribution (V(d)) were measured from dynamic images by use of a one-compartment model. Inter- and intrapatient variability were measured as the coefficient of variability (CV). Data were also obtained for regions of interest in normal liver, spleen, and kidney.
  
  
  RESULTS
  The mean (+/-SD) regional flow in the tumors was 0.46 +/- 0.19 ml(blood)/min/ml(tissue), and the mean V(d) was 0.74 +/- 0.15 ml(blood)/ml(tissue). Variability in tumor flow was greater between (n = 37; CV = 41%) than within (n = 5; CV = 11%) patients. Variability in tumor V(d) was greater between (CV = 21%) than within (CV = 6%) patients. There was a good correlation between the repeat tumor data for both regional flow (rho = 0.82; P = 0.023) and V(d) (rho = 0.89; P = 0.007). Normal tissue variability was also greater between than within patients. In all cases, no statistically significant differences were seen between repeat measurements in the same patient.
  
  
  CONCLUSIONS
  Dynamic C15O2 PET measurements of regional flow are reproducible in patients with predominantly intra-abdominal malignancies and may be useful for the pharmacodynamic evaluation of novel antivascular and antiangiogenic cancer therapeutic agents.
authors.affiliation: Department of Cancer Medicine, MRC Cyclotron Unit, Imperial College London, Hammersmith Hospital, Hammersmith, London, United Kingdom.
authors.forename: Paula
authors.initials: P
authors.lastname: Wells
authors.forename: Terry
authors.initials: T
authors.lastname: Jones
authors.forename: Pat
authors.initials: P
authors.lastname: Price
mesh_terms: D000008:Abdominal Neoplasms / Q000175:diagnosis*; D002245:Carbon Dioxide / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D010104:Oxygen Radioisotopes; D010477:Perfusion; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D013997:Time Factors; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed / Q000379:methods*
chemical_list: D010104:Oxygen Radioisotopes; D002245:Carbon Dioxide