After injection of [18F]FDG (mean 348 ± 18 MBq), PET/CT scans commenced after an uptake time of 60 min. On a separate day following injection of [18F]fluoride (mean 228 ± 15 MBq), scans were performed after an uptake time of 60 min. Imaging comprised a static PET/CT scan using a GE Discovery 710 PET/CT scanner (GE Healthcare, Chicago, USA). Each scan covered the base of the skull to mid-thigh, with an axial field-of-view of 15.7 cm and an 11-slice overlap between bed positions. A low-dose CT scan (140 kV, 10 mA, 0.5 s rotation time and 40 mm collimation) was performed at the start of imaging to provide attenuation correction and an anatomical reference. PET scan duration was set to 3 min per bed position.
PET image reconstruction included standard scanner-based corrections for radiotracer decay, scatter, randoms and dead-time. Emission sinograms were reconstructed with a time-of-flight ordered subset expectation maximisation (OSEM) algorithm (2 iterations, 24 subsets), with a 256 × 256 matrix and a 4-mm full-width at half-maximum (FWHM) Gaussian post-reconstruction smoothing filter on the scanner front end, available from the manufacturer.
PET image reconstruction included standard scanner-based corrections for radiotracer decay, scatter, randoms and dead-time. Emission sinograms were reconstructed with a time-of-flight ordered subset expectation maximisation (OSEM) algorithm (2 iterations, 24 subsets), with a 256 × 256 matrix and a 4-mm full-width at half-maximum (FWHM) Gaussian post-reconstruction smoothing filter on the scanner front end, available from the manufacturer.