Abstract
A spatial bias in brain PET/MR exists compared to PET/CT, due to MR-based attenuation correction (MRAC). We performed an evaluation between four institutions, three PET/MR and four PET/CT systems, using an anthropomorphic brain phantom. We hypothesized, that the spatial bias would be effectively minimized with CT-based attenuation correction (CTAC). METHODS Evaluation protocol was similar to quantifying changes in neurological PET studies. Regional analysis was conducted on eight anatomical VOIs in grey matter on count-normalized, resolution matched and co-registered data. On PET/MR systems, CTAC was applied as the reference method for attenuation correction. RESULTS With CTAC, visual and quantitative differences between PET/MR and PET/CT systems were minimized. Inter-system variation was +3.42 % to -3.29 % in all VOIs in PET/CTs and +2.15 % to -4.50 % in all VOIs for PET/MRs between institutions. PET/MR systems differed by +2.34 % to -2.21 %, +2.04 % to -2.08 % and -1.77 % to -5.37 % when compared to a PET/CT at each institution. The differences between PET/MR and PET/CT systems were not significant (p ≥ 0.05). CONCLUSION Visual and quantitative differences between PET/MR and PET/CT systems can be minimized by an accurate and standardized attenuation correction method. If a similar method to CTAC can be implemented for brain PET/MR imaging, there is no reason why PET/MR should not perform as well as PET/CT.
Teuho, Jarmo