Assessment of porcine bone metabolism by dynamic [F-18]fluoride ion PET: Correlation with bone histomorphometry

The aim of this study was to quantify regional bone blood flow and [F-18]fl uoride ion influx with [F-18]fluoride ion PET and correlate the results wit h specific static and dynamic indices of bone metabolism in healthy pigs. M ethods: During continuous ventilation (fractional concentration of oxygen i n inspired gas = 0.3), dynamic PET scans 120 min in duration were obtained for 9 mini pigs after intravenous injection of 10.0 +/- 1.2 MBq (mean +/- S D) of [F-18]fluoride ion per kilogram of body weight. Iliac crest bone biop sies were performed immediately before the PET scan to determine static and dynamic indices of bone metabolism (i.e., the mineral apposition rate) by bone histomorphometry. Kinetic rate constants describing influx (K-1) and e fflux (k(2)) Of [F-18]fluoride as well as chemisorption and incorporation o f [F-18]fluoride (k(3)) and reverse transport (k(4)) were determined for 6 vertebral bodies in each animal. Blood flow estimates (f) were derived from K-1 values corrected for the permeability-surface area product using a pre viously derived correction algorithm. A rate constant describing the net fo rward transport rate of fluoride (K-i and the fluoride volume flux (K-flux) derived from a 2-tissue-compartment model was calculated and compared with the results of Patlak graphic analysis (K-pat). Results: A significant cor relation was found between mineral apposition rate and Ki (P < 0.005), K-fl ux (P < 0.01), K-pat, K-1, and f (P < 0.05). The values of f, K-i, K-flux a nd K-pat did not correlate significantly with other static or dynamic histo morphometric indices or with age, serum alkaline phosphatase, or parathyroi d hormone levels. The values of f and Ki correlated linearly (y = 0.023 + 0 .32x; r(2) = 0.74; P < 0.001). Conclusion: PET bone studies using [F-18]flu oride ion provide quantitative estimates of bone blood flow and metabolic a ctivity that correlate with histomorphometric indices of bone formation in the normal bone tissue of the mini pig. Therefore, it seem reasonable to as sume that [F-18]fluoride ion PET can reduce the number of invasive bone bio psies, thus facilitating follow-up of patients with metabolic bone diseases .