@article {Teuho818, author = {Jarmo Teuho and Jarkko Johansson and Jani Linden and Adam Espe Hansen and S{\o}ren Holm and Sune H. Keller and Gaspar Delso and Patrick Veit-Haibach and Keiichi Magota and Virva Saunavaara and Tuula Tolvanen and Mika Ter{\"a}s and Hidehiro Iida}, title = {Effect of Attenuation Correction on Regional Quantification Between PET/MR and PET/CT: A Multicenter Study Using a 3-Dimensional Brain Phantom}, volume = {57}, number = {5}, pages = {818--824}, year = {2016}, doi = {10.2967/jnumed.115.166165}, publisher = {Society of Nuclear Medicine}, abstract = {A spatial bias in brain PET/MR exists compared with PET/CT, because of MR-based attenuation correction. We performed an evaluation among 4 institutions, 3 PET/MR systems, and 4 PET/CT systems using an anthropomorphic brain phantom, hypothesizing that the spatial bias would be minimized with CT-based attenuation correction (CTAC). Methods: The evaluation protocol was similar to the quantification of changes in neurologic PET studies. Regional analysis was conducted on 8 anatomic volumes of interest (VOIs) in gray matter on count-normalized, resolution-matched, coregistered 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. Intersystem variation between institutions was +3.42\% to -3.29\% in all VOIs for PET/CT and +2.15\% to -4.50\% in all VOIs for PET/MR. PET/MR systems differed by +2.34\% to -2.21\%, +2.04\% to -2.08\%, and -1.77\% to -5.37\% when compared with a PET/CT system at each institution, and these differences 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 method of attenuation correction. If a method similar to CTAC can be implemented for brain PET/MRI, there is no reason why PET/MR should not perform as well as PET/CT.}, issn = {0161-5505}, URL = {https://jnm.snmjournals.org/content/57/5/818}, eprint = {https://jnm.snmjournals.org/content/57/5/818.full.pdf}, journal = {Journal of Nuclear Medicine} }