Evaluation of a short dynamic 18F-fluoride PET/CT scanning method to assess bone metabolic activity in spinal orthopedics

Abstract

Objective: A complication after spinal fusion surgery is pseudarthrosis, but its radiological diagnosis is of limited value. 18F-fluoride PET with its ability to assess bone metabolism activity could be of value. The goal of this study was to assess the clinical feasibility of calculating the static standardized uptake value (SUV) from a short dynamic scan without the use of blood sampling, thereby obtaining all dynamic and static parameters in a scan of only 30 min. This approach was tested on a retrospective patient population with persisting pain after spinal fusion surgery. Methods: In 16 patients, SUVs (SUVmax, SUVmean) and kinetic parameters (K1, k2, k3, vb, Ki,NLR, K1/k2, k3/(k2 + k3), Ki,patlak) were derived from static and dynamic PET/CT scans of operated and control regions of the spine, after intravenous administration of 156–214 MBq 18F-fluoride. Parameter differences between control and operated regions, as well as between pseudarthrosis and fused segments were evaluated. SUVmean at 30 and 60 min was calculated from kinetic parameters obtained from the dynamic data set (SUVmean,2TCM). Agreement between measured and calculated SUVs was evaluated through Bland–Altman plots. Results: Overall, statistically significant differences between control and operated regions were observed for SUVmax, SUVmean, Ki,NLR, Ki,patlak, K1/k2 and k3/(k2 + k3). Diagnostic CT showed pseudarthrosis in 6/16 patients, while in 10/16 patients, segments were fused. Of all parameters, only those regarding the incorporation of bone [Ki,NLR, Ki,patlak, k3/(k2 + k3)] differed statistically significant in the intervertebral disc space between the pseudarthrosis and fused patients group. The mean values of the patient-specific blood clearance rate $$\tau^{*}$$τ∗ differed statistically significant between the pseudarthrosis and the fusion group, with a p value of 0.011. This may correspond with the lack of statistical significance of the SUV values between pseudarthrosis and fused patients. Bland–Altman plots show that calculated SUVmean,2TCM values corresponded well with the measured SUVmean values. Conclusion: This study shows the feasibility of a 30-min dynamic 18F-fluoride PET/CT scanning and this may provide dynamic parameters clinically relevant to the diagnosis of pseudarthrosis.