title: Long-term precision of 18F-fluoride PET skeletal kinetic studies in the assessment of bone metabolism.
abstract: (18)F-Fluoride PET allows noninvasive evaluation of regional bone metabolism and has the potential to become a useful tool for assessing patients with metabolic bone disease and evaluating novel drugs being developed for these diseases. The main PET parameter of interest, termed K(i), reflects regional bone metabolism. The aim of this study was to compare the long-term precision of (18)F-fluoride PET with that of biochemical markers of bone turnover assessed over 6 mo.
  
  
  METHODS
  Sixteen postmenopausal women with osteoporosis or significant osteopenia and a mean age of 64 y underwent (18)F-fluoride PET of the lumbar spine and measurements of biochemical markers of bone formation (bone-specific alkaline phosphatase and osteocalcin) and bone resorption (urinary deoxypyridinoline) at baseline and 6 mo later. Four different methods for analyzing the (18)F-fluoride PET data were compared: a 4k 3-compartmental model using nonlinear regression analysis (K(i-4k)), a 3k 3-compartmental model using nonlinear regression analysis (K(i-3k)), Patlak analysis (K(i-PAT)), and standardized uptake values.
  
  
  RESULTS
  With the exception of a small but significant decrease in K(i-3k) at 6 mo, there were no significant differences between the baseline and 6-mo values for the PET parameters or biochemical markers. The long-term precision, expressed as the coefficient of variation (with 95% confidence interval in parentheses), was 12.2% (9%-19%), 13.8% (10%-22%), 14.4% (11%-22%), and 26.6% (19%-40%) for K(i-3k), K(i-PAT), mean standardized uptake value, and K(i-4k), respectively. For comparison, the precision of the biochemical markers was 10% (7%-15%), 18% (13%-27%), and 14% (10%-21%) for bone-specific alkaline phosphatase, osteocalcin, and urinary deoxypyridinoline, respectively. Intraclass correlation between the baseline and 6-mo values ranged from 0.44 for K(i-4k) to 0.85 for K(i-3k). No significant correlation was found between the repeated mean standardized uptake value measurements.
  
  
  CONCLUSIONS
  The precision and intraclass correlation observed for K(i-3k) and K(i-PAT) was equivalent to that observed for biochemical markers. This study provided initial data on the long-term precision of (18)F-fluoride PET measured at the lumbar spine, which will aid in the accurate interpretation of changes in regional bone metabolism in response to treatment.
authors.affiliation: King's College London, Osteoporosis Screening and Research Unit, Guy's Hospital, London, United Kingdom. michelle.frost@kcl.ac.uk
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Frost
authors.forename: Glen M
authors.initials: GM
authors.lastname: Blake
authors.forename: So-Jin
authors.initials: SJ
authors.lastname: Park-Holohan
authors.forename: Gary J R
authors.initials: GJ
authors.lastname: Cook
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Curran
authors.forename: Paul K
authors.initials: PK
authors.lastname: Marsden
authors.forename: Ignac
authors.initials: I
authors.lastname: Fogelman
mesh_terms: D000368:Aged; D015415:Biomarkers; D001842:Bone and Bones / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005260:Female; D005462:Fluorine Radioisotopes; D006801:Humans; D007700:Kinetics; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000378:metabolism; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D017698:Postmenopause; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D015415:Biomarkers; D005462:Fluorine Radioisotopes