Differential functional benefits of ultra highfield MR systems within the language network.
Bottom Line: Improvement is expected from ultra highfield systems but studies on possible benefits for cognitive networks are lacking.During data acquisition and analysis we made particular efforts to minimize effects not related to static magnetic field strength differences.We conclude that functional UHF benefits are evident, however these depend crucially on the brain region investigated and the ability to control local artifacts.
Affiliation: Study Group Clinical fMRI, Department of Neurology, Medical University of Vienna, Austria; High Field MR Center, Medical University of Vienna, Austria; Department of Neurology, Medical University of Vienna, Austria.Show MeSH
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Mentions: The dissociation of UHF benefits within the language network was considerable in our population (Broca 0/6–Wernicke 5/6 parameters significant). This indicates that a functional UHF benefit is readily achievable for superior temporal and central areas (motor system, Beisteiner et al., 2011), however improvements were not evident for inferior frontal areas. The most likely explanation for this is the increased susceptibility-related field gradients in inferior frontal brain areas causing increased artifacts at UHF. This is evidenced by the original functional EPI images (Fig. 3) and the field map results. Field maps show significantly larger gradients in B0 in Broca's compared to Wernicke's area, causing increased signal dropouts. As gradients in B0 scale approximately linearly with field strength, signal loss in Broca's area is considerably lower with our 3 T data. As with our previous study, ghosting and head motion artifacts were also larger at 7 T compared to 3 T, although these should not differentially affect Broca's and Wernicke's areas. The same is true for possible environmental factors like psychological effects due to varying comfort (the 3 T system has a shorter bore, and is more brightly lit). Such environmental factors are unlikely to confound signal changes such that UHF sensitivity is only reduced for Broca's area.
Affiliation: Study Group Clinical fMRI, Department of Neurology, Medical University of Vienna, Austria; High Field MR Center, Medical University of Vienna, Austria; Department of Neurology, Medical University of Vienna, Austria.