Dynamic PET Imaging of Neuroinflammation

The mice were anaesthetized with 2–2.5% isoflurane inhalation and kept on a heating pad. They were first imaged with CT for attenuation correction (Inveon Multimodality PET/CT, Siemens Medical Solutions, Knoxville, TN, USA). After CT, approximately 10 MBq of ¹⁸F-GE-180 was administered as an intravenous bolus injection via a tail vein cannula, and a 30-minute dynamic PET was started at the same time with the injection. After PET, 100 µl of intravenous contrast agent (eXIA160XL, Binitio Biomedical Inc., Ottawa, ON, Canada) was injected, and a high-resolution CT was performed as described in [20 (link)]. The PET images were reconstructed with 2D ordered-subset expectation maximization (OSEM2D) algorithm with two iterations into 2 × 30 s, 4 × 60 s, and 5 × 300 s time frames, and CT images were reconstructed with a Feldkamp-based algorithm. The radioactivity concentration in tissues was analysed by defining regions of interest (ROIs) with Carimas 2.9 program (Turku PET Centre, Turku, Finland). The ROI for blood was placed in the left jugular vein. The results were extracted as mean standardized uptake values (SUV) and were plotted as time-activity curves. Mean SUVs at 20–30 min after injection were utilized in numerical calculations.