Magnetom biograph mmr

All experiments were performed on a clinical 3-Tesla hybrid PET/MR scanner (Magnetom Biograph mMR, Siemens Healthineers, Erlangen, Germany) with a 20-channel head coil. Rabbits were positioned head first in prone position. For anatomic orientation, a transversal T1-weighted fat-saturated Dixon sequence (repetition time [TR] 4.76, echo time [TE] 1.49 ms, matrix 512 × 512 mm, voxel size .5 × .5 × 2.0 mm³ and coverage of the complete liver) was performed in the abdominal region of the rabbits before MRE and PET scans.

Whole-body PET/MRI examinations were performed on a Magnetom Biograph mMR (Siemens Healthcare Sector, Erlangen, Germany), using lutetium oxyorthosilicate-based avalanche photodiodes (APD) for PET-acquisition. PET/MRI scans were obtained with an average delay of 102±39 min after ¹⁸F-FDG injection and a mean activity of 201±69 MBq. Whole body PET scans, covering the body from skull-base to mid-thighs, were performed with 5 to 6 bed positions and an acquisition time of 8 minutes each. PET images were reconstructed using the iterative algorithm OSEM, 3 iterations and 21 subsets, Gaussian filter with 4 mm full width at half maximum (FWHM) and a 344×344 image matrix. PET data were automatically attenuation corrected using a four-compartment-model attenuation map (µ-map) calculated from fat-only and water-only as obtained from Dixon-based sequences. Simultaneous whole-body MR imaging was performed with a dedicated mMR head and neck coil and phased-array body surface coils. The overall examination time of the PET/MR protocol for whole-body staging amounted to 35±5 min., encompassing the following sequences:
For contrast-enhanced imaging, 0.1 mmol/kg Gadobutrol (Gadovist, Bayer HealthCare, Germany), followed by a saline flush of 20 ml, was injected intravenously at 2 ml/s using an automated injector (Spectris solaris EP MR Injection System, Medrad, Germany).