Cross-validation study between the HRRT and the PET component of the SIGNA PET/MRI system with focus on neuroimaging.

Background: The Siemens high-resolution research tomograph (HRRT - a dedicated brain PET scanner) is to this day one of the highest resolution PET scanners; thus, it can serve as useful benchmark when evaluating performance of newer scanners. Here, we report results from a cross-validation study between the HRRT and the whole-body GE SIGNA PET/MR focusing on brain imaging. Phantom data were acquired to determine recovery coefficients (RCs), % background variability (%BG), and image voxel noise (%). Cross-validation studies were performed with six healthy volunteers using [C]DTBZ, [C]raclopride, and [F]FDG. Line profiles, regional time-activity curves, regional non-displaceable binding potentials (BP) for [C]DTBZ and [C]raclopride scans, and radioactivity ratios for [F]FDG scans were calculated and compared between the HRRT and the SIGNA PET/MR.

Results: Phantom data showed that the PET/MR images reconstructed with an ordered subset expectation maximization (OSEM) algorithm with time-of-flight (TOF) and TOF + point spread function (PSF) + filter revealed similar RCs for the hot spheres compared to those obtained on the HRRT reconstructed with an ordinary Poisson-OSEM algorithm with PSF and PSF + filter. The PET/MR TOF + PSF reconstruction revealed the highest RCs for all hot spheres. Image voxel noise of the PET/MR system was significantly lower. Line profiles revealed excellent spatial agreement between the two systems. BP values revealed variability of less than 10% for the [C]DTBZ scans and 19% for [C]raclopride (based on one subject only). Mean [F]FDG ratios to pons showed less than 12% differences.

Conclusions: These results demonstrated comparable performances of the two systems in terms of RCs with lower voxel-level noise (%) present in the PET/MR system. Comparison of in vivo human data confirmed the comparability of the two systems. The whole-body GE SIGNA PET/MR system is well suited for high-resolution brain imaging as no significant performance degradation was found compared to that of the reference standard HRRT.