Development of a full-ring “add-on PET” prototype: A head coil with DOI-PET detectors for integrated PET/MRI

We evaluated performance of the full-ring prototype in simultaneous measurements of the integrated PET/MRI. We obtained spatial resolutions of 2.3 mm at the center of the field-of-view (FOV) and lower than 3.5 mm in the whole FOV. The energy resolution of 19.4% was obtained for 511 keV gamma-rays. In addition, we observed no degradation of PET performance caused by the MRI measurement. The signal-to-noise ratio (SNR) of the MRI image was 209.4 in simultaneous measurements with the PET. The maximum ΔB0 and maximum difference of the secondary magnetic field due to the eddy current effect were smaller than 0.8 ppm and ±5.0 μT, respectively. We concluded that sufficient spatial resolution and detector performance of the PET were obtained for the add-on PET prototype even in the simultaneous measurements with the MRI. The influence of the PET detectors on the static magnetic field and the SNR of the MRI images were not problems, although the eddy current effect must be suppressed.