Nucline v2

The biodistribution of [¹⁸F]RM273 in mice was assessed by dynamic small animal PET (Nanoscan, Mediso, Budapest, Hungary) 60 min recordings, followed by T1 weighted (GRE, TR/TE = 15.0/2.4 ms, 252/252, FA = 25°) imaging for anatomical correlation and attenuation correction. The mice weighing 31.7 ± 3.8 g were anaesthetized with 2% isoflurane in 60% oxygen and placed on a thermostatically heated animal bed. [¹⁸F]RM273 (7.2 ± 1.1 MBq) was injected i.v. into the lateral tail vein (bolus within 5 s) at the start of the PET-acquisition. List mode PET data were binned as a series of attenuation-corrected sinogram frames (12 × 10 s, 6 × 30 s, 5 × 60 s and 10 × 300 s) and were reconstructed by Ordered Subset Expectation Maximization (OSEM3D) with four iterations, six subsets, and a voxel size of 0.4 mm³ (Nucline v2.01, Mediso, Hungary). The analysis of reconstructed datasets was performed with PMOD software (v4.103, PMOD Technologies LLC, Zurich, Switzerland). GraphPad Prism (v9, San Diego, CA, USA) was used to calculate the area under the curve (AUC), as well as to determine the peak TAC half-life time by fitting of time–activity curves with dissociation one phase exponential decay setting t₀ at peak of TAC.

The dynamic biodistribution of the radiotracers was assessed by small animal PET (nanoscan, Mediso, Hungary) over 60 min PET with a subsequently T1 weighted MR. Anaesthetized (2% isofluran, carrier gas mixture of 40% air and 60% O₂) female CD-1 mice (bodyweight = 30.3 ± 1.1 g) were kept during imaging on a heated animal bed to sustain body temperature and were pretreated with vehicle (0.9% saline) and α-CHC-Na (25 mg/kg bodyweight) prior to tracer application ([¹⁸F]1: 5.8 ± 0.2 MBq, 1.1 fmol/g bodyweight and [¹⁸F]FACH: 5.9 ± 0.5 MBq, 3.7 ± 1.8 fmol/g), whereby all injections were administered intravenously. The acquisitions were performed in normal mode and a coincidence Mode 1–5. For subsequent dynamic reconstructions, list mode data were sorted into sinograms (12 × 10 s, 6 × 30 s, 5 × 60 s, and 10 × 300 s). The frames were reconstructed by Ordered Subset Expectation Maximization applied to 3D sinograms (OSEM3D) with an attenuation correction with 4 iterations, 6 subsets and a voxel size of 0.4 mm³ (Nucline v2.01, Mediso, Hungary). Analyses of reconstructed studies were performed with PMOD software (v4.005, PMOD Technologies LLC, Zurich, Switzerland) and results are expressed in Standardized Uptake Value (SUV).

The mice underwent functional positron emission tomography (PET) and 1T anatomical magnetic resonance imaging (MRI; Mediso Medical Imaging Systems). Anesthesia with isoflurane was initiated with the mouse placed in an acrylic glass chamber and maintained with respiration in a mask during the scan. A bolus of [¹⁸F]-Flurodeoxyglucose (FDG) (~15 MBq/animal) was injected via a tail vein catheter, and PET scanning was performed for 50 to 70 min after injection, followed by a 25 min T1 weighted MR-scan. Body temperature and respiration frequency were monitored during anesthesia.
A static PET image was reconstructed with a three-dimensional ordered subset expectation algorithm (Tera-Tomo 3D; Mediso Medical Imaging Systems) with four iterations and six subsets and a voxel size of 0.4 × 0.4 × 0.4 mm³. Data were corrected for dead-time, decay, and randomness using a delayed coincidence window without corrections for attenuation and scatter. A specialist in nuclear medicine identified tumors by visual inspection of the PET/MR-scans using Nucline v2.01 (Mediso Medical Imaging Systems). Borders of the tumors were drawn manually, and volume was calculated using HERMES (Hermes Medical Solutions).