Inveon research workspace software

Following acquisition, data were histogrammed into 45 frames (10 × 3 s, 6 × 5 s, 8 × 30 s, 5 × 60 s, 6 × 300 s, 8 × 600s for data acquired up to 120 min). For data acquired up to 140 min, an additional 2 × 600 s frames were added. Data were reconstructed using filtered back projection with CT attenuation correction, adjusting for random noise, scatter, and radiotracer decay. Image processing was carried out using the Inveon Research Workspace software (Siemens, USA). The CT image was manually co-registered to the reconstructed PET image using the outline of the skull as a reference. For each subject, the percentage-injected dose was normalised for body weight and injected activity to provide standardised uptake values (SUV). The striatal (0.70 mm³) and cerebellar (the reference region; rectangular; 1.1 mm³) regions of interest (ROI) were placed manually on summation radioactivity images guided by CT and mouse brain anatomy based on previous studies [6 (link), 8 (link), 17 (link)].

Mice were injected via the tail vein with a mean activity of 8.90 ± 1.55 MBq (Mean ± SD) ¹⁸F-FDG in 0.2 mL 0.9 % isotonic saline solution. Prior to injection all mice were fasted for approximately 12 h to minimize the variation in ¹⁸F-FDG uptake [17 (link)]. For injection, distribution, and scanning, all mice were kept anaesthetized with 3 % sevoflurane (Abbott Scandinavia AB, Solna, Sweden) mixed with 35 % O₂ and 65 % N₂. Body temperature was kept stable by external heating device when anaesthetized, and positioned on a heating pad during scan. ¹⁸F-FDG PET/CT imaging was performed on Siemens Inveon® Small Animal Scanner (Siemens Medical Systems, PA, USA). The protocol included a five minute PET scan followed by a CT scan with attenuation correction to be used for reconstruction. Reconstruction of PET scans were performed using maximum a posteriori (MAP) reconstruction algorithm (voxel size: 0.815 × 0.815 × 0.796 mm; resolution (FWHM) 1.2 mm). Reconstructed images were analyzed with Inveon Research Workspace software (Siemens Medical Systems, PA, USA). Tracer uptake was determined as mean and maximum % injected dose pr. gram of tumor (%ID/g) (1 gram per cm³), and mean and maximum standardized uptake value (SUV), corrected for decay.