Standardized Whole-Body FDG-PET/CT Protocol

Whole body FDG-PET/CT was performed on a Discovery ST16 PET/CT scanner (GE Healthcare, Little Chalfont, Great Britain). The patients underwent a low-dose non-contrast-enhanced CT scan (120 kV, auto mA 20–100 mA, noise index 28, Pitch 1,375:1) with 3,75 mm slice thickness, matching that of the PET emission. After 4 hours of fasting the patients received an intravenous bolus injection of mean 185 MBq FDG (2 MBq/kg). Image acquisition began one hour after injection. A CT scan for attenuation correction was followed by PET emission, 3 minutes per bed position, from head to toe. Attenuation-corrected emission images were reconstructed with an iterative algorithm and the reconstructed images were recalculated to standardized uptake value (SUV) images, corrected for patient body weight and amount of injected FDG. The software that was used for ROI definition and SUVmax read out in this study was Carestream Vue PACS version 11.3.1.1 (Carestream Health, NY, USA). The tumors were delineated with circular regions of interest (ROIs) in the PET section measuring the SUV_max^{50 (link)}. The assessment of the PET examinations was performed by professor AS who has 27 years of experience. All measurements of SUVmax in both injected and not injected metastases were repeated three times and the results were similar.