Nanoscan pet mri system

Tumor growth was monitored using magnetic resonance imaging (MRI) with a frequency depending on the tumor model and the corresponding growth rate (e.g., weekly imaging for U87_mCherry tumors and at least every two weeks for G7_mCherry). MRI examinations were acquired with a 1.0 Tesla nanoScan^® PET/MRI system (Mediso Medical Imaging Systems, Budapest, Hungary) using the mouse head coil. For this purpose, Isoflurane (2–2.5% in oxygen; Baxter Germany) was used for anesthesia, and mice were positioned in the MRI bed with an integrated warming system. Bed temperature (37 °C), as well as breathing frequency, were monitored during the whole imaging procedure.
First, a T2-weighted 3D fast spin echo sequence with a field of view (FOV) covering the head of the mouse was performed (repetition time (TR): 1000 ms, effective echo time (TE): 97.7 ms, FOV: 31.3 mm, slice thickness: 0.23 mm, number of slices: 90). Second, a 3D gradient echo spoiled T1-weighted sequence was applied 10 min after i.p. injection of 5 mL/kg bw Omniscan^® (GE Healthcare, Chicago, IL, USA) Gadolinium-based contrast agent at the same position (TR: 15 ms, TE: 3.1 ms, flip angle: 25°, FOV: 60 mm, slice thickness: 0.23 mm, number of slices: 90). Data were analyzed using the InterviewFusion™ software (Mediso Medical Imaging Systems, Budapest, Hungary); the investigator was blinded to the therapy at the moment of evaluation.

PET/MRI fused imaging was performed using the nanoScan PET/MRI system (1T, Mediso, Hungary). Mice were fasted for 8 h before imaging, maintained at a constant body temperature, and injected intravenously via the tail vein with 6.5 ± 1.0 MBq in 0.2 mL of FDG. Mice were kept under anaesthesia (1.5% isoflurane in 100% O₂ gas). The T1-weighted with Gradient-echo (GRE) 3D sequence (TR = 25 ms, TEeff = 3.4, FOV = 64 mm, matrix = 128 × 128) was acquired during the FDG uptake period. Static PET images were acquired for 10 min in a 1–5 coincident in a single field of view in the MRI range. Body temperature was maintained with a heating pad on the animal bed (Multicell, Mediso, Hungary) and a pressure sensitive pad was used for respiratory triggering. PET images were reconstructed by Tera-Tomo 3D in full detector mode with all the corrections on, high regularisation, and eight iterations. Three-dimensional volume of interest (VOI) analysis of the reconstructed images was performed using the InterView Fusion software package (Mediso, Hungary) and applying standard uptake value (SUV) analysis. The VOI was fixed in a sphere of 2 mm diameter, which was drawn for the tumour and muscle sites. The SUV of each VOI site was calculated using the following formula SUV mean = (tumour radioactivity in the tumour VOI with the unit of Bq/cc × body weight) divided by injected radioactivity^{59 (link)}.