Vivoquant v2

PET/CT images were acquired with a nanoScan^® PET/CT (Mediso Medical Imaging Systems, Budapest, Hungary) scanner operating in list mode using a 400–600 keV energy window and a coincidence window of 1:3. CT scans were acquired for anatomical reference and attenuation correction (55 keV X-ray, exposure time 1000 ms, and 360 projections and pitch 1). PET projection data were reconstructed using the Tera-tomo^® software package provided with the scanner —a Monte Carlo-based fully 3D iterative algorithm with four iterations, six subsets, and 0.4 mm isotropic voxel size; corrections for attenuation, scatter, and dead-time were enabled. The data were then visualised and quantified using VivoQuant^© v.2.50 (InviCro, Boston, MA, USA) software. SPECT/CT imaging was performed on a NanoSPECT/CT Silver Upgrade scanner (Mediso; 4 heads, 4 × 9 1.0 mm multipinhole collimators) in helical scanning mode using energy windows centred around 93.20 ± 20% keV (primary), 184.60 ± 20% keV (secondary), and 300.00 ± 20% keV (tertiary). CT images were acquired using 45 kVp tube voltage and 1000 ms exposure time in 180° projections. SPECT/CT data sets were reconstructed using the HiSPECT 1.4.2611 (SciVis, Gottingen, Germany) reconstruction software package using standard reconstruction with 35% smoothing and 9 iterations. Images were coregistered and analysed using VivoQuant v2.50 (InviCro, Needham, MA, USA).

All image reconstructions were performed using Siemens’ Inveon Acquisition Workplace v2.0 software package (Siemens Medical Solutions, Knoxville, TN) (details are provided in the ESM). PET images were coregistered to corresponding CT data using VivoQuant v2.5 image processing software (inviCRO, LLC, Boston, MA) and were subsequently coregistered to a 3D mouse brain atlas (included in VivoQuant software package) so that brain [¹⁸F]DPA-714 biodistribution could be quantified. PET imaging data were reported in terms of percent injected dose per gram of tissue (%ID/g), calculated as a ratio of tissue radioactivity concentration (Bq/g) at time of scan to total injected activity (Bq) at time of scan.

Mice were imaged in the InSyTe FLECT/CT system (TriFoil Imaging, Chatsworth, CA). CT was performed using the following parameters: tube voltage 31 kV, tube current 500 µA, and exposure time 150 ms. The entire object was scanned according to the principle of continuous helical radiation of 720 projections with 360-degree coverage. Image resolution reached 25 × 25 × 25 microns. The total time of the procedure was 15 min. FLECT was performed using the 780 nm laser, and the fluorescence signal was filtered with 853 nm filter emission. Exposure time was 17.5 ms. The entire object was scanned according to the principle of continuous helical radiation of 116 projections with 360-degree coverage. Image resolution reached 1 mm × 1 mm × 1 mm. The total time of the procedure was 33 min 12 s. The images were reconstructed using the TriFoil Imaging software. CT and FLECT reconstructions were combined using VivoQuant v2.5 (Invicro, Boston, MA).