GE Signa integrated PET/MR: NEMA PET performance measurements

We evaluated the PET performance of the GE SIGNA integrated PET/MR (SGINA) and adjusted potential post-filtering settings to harmonise image quality and quantitative accuracy between different PET-systems at our institution. METHODS: The NEMA NU 2-2007 protocol was followed for studying the PET performance of the SIGNA. The following measurements were performed: spatial resolution; scatter fraction, sensitivity; accuracy of correction for count losses and randoms. Furthermore, a NEMA image quality phantom was measured with and without simultaneous MR acquisition. The reconstructed spatial resolution (SR) and mean recovery coefficients (RCmean) in a TOF-OSEM reconstruction (VPFX, 2 subsets 28 iterations, no post-filtering) were determined using the method of [1]. Moreover, we analysed the effect of different post-filters to obtain a SR that is comparable to a Siemens Hirez PET/CT (HIREZ) at our institution. RESULTS: An transaxial SR of 4.1 and 5.1 mm in full width at half maximum (FWHM) was measured at 1 and 10 cm off-center. In the axial direction values were 6.1 and 6.9 mm, respectively. The system sensitivity was 21.8 cps/kBq along the center and 21.2 cps/kBq and at 10 cm off-center. The scatter fraction was 43.35%, and the peak noise-equivalent count rate was 216 kcps at 18.6 kBq/mL. The maximum absolute value of the relative count rate error due to dead-time losses and randoms was 2.92%. The average lung residual error was 1.6% for PET only and 2.1% for PET with simultaneous MR. The reconstructed SR of the TOF-OSEM reconstruction was 4.4 mm resulting in RCmeans of 0.87, 0.85, 0.80, 0.75, 0.70, 0.62 for the six spheres in the NEMA phantom. A Gaussian post-filtering with 5.4mm was necessary to match the SR of the SIGNA with the one of the HIREZ (7mm). CONCLUSION: The SIGNA offers a very promising PET performance and reconstructed SR which is crucial for lesion detectability and reduced partial volume effects. REFERENCES: [1] Hofheinz et al., “Effects of cold sphere walls in PET phantom measurements on the volume reproducing threshold.”, Med Phys 40:082503, 2013