PET performance of the GEMINI TF PET — MR: The world´s first whole body PET — MRI scanner

The GEMINI TF PET-MRI (Philips Healthcare, Cleveland, OH) is a newly released whole body hybrid imaging system with a Philips Achieva 3T system and a Philips TF (TruFlight) PET. We report the standard NEMA NU2 measurements for the scanner. Compared to PET-CT, modifications to the PET were made to avoid mutual system interference and deliver uncompromising performance which is equivalent to the standalone systems. The PET gantry was redesigned to introduce magnetic shielding for the PMTs. Stringent electromagnetic noise requirements of the MR system necessitated the removal of PET gantry electronics to be housed in the PET-MR equipment room. All PET calibrations and measurements were done with the MRI ramped to 3T, shimmed and calibrated. Measurements were performed as described in NEMA standard manual. GEMINI TF PET-CT typical NEMA values were compared to PET-MR (n≥4 for PET-MR data). Spatial resolution and sensitivity were comparable to PET-CT results. Timing resolution and energy resolution of the PET-MR system (not NEMA standard measurements) were measured to be 520 ps and 12%, respectively. Image quality measurements performed with IEC phantom yielded results comparable to PET-CT. The NEMA results obtained with PET-MR are equivalent to typical GEMINI TF PET-CT results. System energy and timing resolution were comparable to PET-CT demonstrating the effect of magnetic shielding to maintain the PMTs in normal flux levels. In conclusion, we report the design of a whole-body hybrid PET-MRI system where PET performance is comparable to standalone GEMINI TF PET-CT system.