A Short Dynamic Scan Method of Measuring Bone Metabolic Flux Using [¹⁸F]NaF PET

[¹⁸F]NaF PET measurements of bone metabolic flux (K_i) are conventionally obtained with 60-min dynamic scans analysed using the Hawkins model. However, long scan times make this method expensive and uncomfortable for subjects. Therefore, we evaluated and compared measurements of K_i with shorter scan times analysed with fixed values of the Hawkins model rate constants. The scans were acquired in a trial in 30 postmenopausal women, half treated with teriparatide (TPT) and half untreated. Sixty-minute PET-CT scans of both hips were acquired at baseline and week 12 after injection with 180 MBq [¹⁸F]NaF. Scans were analysed using the Hawkins model by fitting bone time-activity curves at seven volumes of interest (VOIs) with a semi-population arterial input function. The model was re-run with fixed rate-constants for dynamic scan times from 0-12 min increasing in 4-min steps up to 0-60 min. Using the Hawkins model with fixed rate-constants, K_i measurements with statistical power equivalent or superior to conventionally analysed 60-min dynamic scans were obtained with scan times as short as 12 min.