Faculty of Psychology and Neuroscience Fast quantitative T1-mapping at ultra-high field using inversion-recovery echo planar imaging Dimo Ivanov, Benedikt A Poser, Sriranga Kashyap, Martin Havlicek, and Kâmil Uludağ Maastricht Brain Imaging Center, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Netherlands RESULTS/DISCUSSION • The generation of high-resolution distortion-matched quantitative T1 maps at 7 and 9.4 T using an optimized inversion-recovery EPI sequence is possible • Anatomical data that is geometrically identical to the functional data provides means to localize brain activations more accurately • M0 maps have proton density and T2 *-weighting and therefore offer complementary anatomical information especially in subcortical regions • The T1 values of grey and white matter increase at 9.4 in comparison to 7T • The inversion efficiency was at least 95% throughout the brains of all participants at 7T. At 9.4T comparable inversion efficiency was achieved in most of the brain except for regions around and inferior to the left basal ganglia. Parallel transmission[7] can be used to increase B1 in these areas • The presented approach allows high-resolution accurate quantitative T1 mapping in less than 6 minutes, which makes it also applicable for clinical studies, as changes in T1 have been linked to many neurological disorders • Further scan time reductions using simultaneous multi-slice techniques[8,9] are still possible INTRODUCTION • In a typical fMRI analysis, the results are displayed overlaid on an anatomical image • A good co-registration between the fMRI and anatomical data is essential to achieve accurate localization of function • The differing image properties (contrast, distortions) of both datasets pose a challenge for the registration and often lead to errors • Co-registration between functional and anatomical data is most important, but also most difficult, in high-resolution fMRI at ultra-high field (B0- and B1-inhomogeneities) • Ultra-high field (≥7 T) offers fMRI substantial benefits due to increases in signal-to-noise ratio and specificity[1] • The problem with co-registration between anatomical and functional data can be circumvented by acquiring distortion-matched anatomical images using inversion-recovery EPI with identical readout parameters • We demonstrate the feasibility of the approach at both 7 and 9.4 Tesla, utilizing recent advances in methods for fast quantitative T1-mapping[2] References [1] Uludağ et al. Neuroimage, 2009. 48:150-65 [2] Renvall et al. Proc. ISMRM, 2014. 22:4282 [3] Shajan et al. MRM, 2013 71:870-9 [4] Norris DG. J Magn Reson Imaging, 2000. 11:445-51 [5] Clare & Jezzard. MRM, 2001. 45:630-4 [6] Hurley et al. MRM, 2010. 63:51-8 [7] Bazin et al. Neuroimage, 2014. 93 Pt 2:201-9. [7] Grissom et al. MRM, 2006. 56:620-9; [8] Moeller et al. MRM, 2010. 63:1144-53 [9] Setsompop et al. MRM, 2012. 67:1210-24 CONCLUSION The approach presented delivers geometrically-matched reference for fMRI studies at ultra-high field and can be applied for tissue segmentation and brain morphometry. METHODS • 7T and 9.4T Siemens scanners with 32-channel (Nova Medical) and 31- channel[3] head coils, respectively • Five healthy volunteers (28±4 years old) participated after giving informed consent • The acquisition rapidly obtains several inversion times (TI) by placing EPI readouts following an inversion pulse and permuting the slice order each repetition[4,5] • The slice-order permutation was done stepping through several slices at a time according to the reordering scheme proposed in Renvall 2014[2] • The inversion was done using an optimized 10 ms tr-FOCI pulse[6], which achieves high inversion efficiency at ultra-high field despite B1- inhomogeneities and SAR constraints • Acquisition parameters: 1 mm3 isotropic resolution; TR/TIs/slices/step = 10 s/32/128/4; TE = 24 ms (7T) & 20 ms (9.4T); TA = 5 min 30 s • Quantitative M0, T1 and inversion eff