Improving fMRI in signal drop-out regions at 7 T by using tailored radio-frequency pulses: application to the ventral occipito-temporal cortex

TY - JOUR

T1 - Improving fMRI in signal drop-out regions at 7 T by using tailored radio-frequency pulses

T2 - application to the ventral occipito-temporal cortex

AU - Rua, Catarina

AU - Wastling, Stephen J

AU - Costagli, Mauro

AU - Symms, Mark R

AU - Biagi, Laura

AU - Cosottini, Mirco

AU - Del Guerra, Alberto

AU - Tosetti, Michela

AU - Barker, Gareth J

PY - 2017/9/20

Y1 - 2017/9/20

N2 - OBJECTIVE: Signal drop-off occurs in echo-planar imaging in inferior brain areas due to field gradients from susceptibility differences between air and tissue. Tailored-RF pulses based on a hyperbolic secant (HS) have been shown to partially recover signal at 3 T, but have not been tested at higher fields.MATERIALS AND METHODS: The aim of this study was to compare the performance of an optimized tailored-RF gradient-echo echo-planar imaging (TRF GRE-EPI) sequence with standard GRE-EPI at 7 T, in a passive viewing of faces or objects fMRI paradigm in healthy subjects.RESULTS: Increased temporal-SNR (tSNR) was observed in the middle and inferior temporal lobes and orbitofrontal cortex of all subjects scanned, but elsewhere tSNR decreased relative to the standard acquisition. In the TRF GRE-EPI, increased functional signal was observed in the fusiform, lateral occipital cortex, and occipital pole, regions known to be part of the visual pathway involved in face-object perception.CONCLUSION: This work highlights the potential of TRF approaches at 7 T. Paired with a reversed-gradient distortion correction to compensate for in-plane susceptibility gradients, it provides an improved acquisition strategy for future neurocognitive studies at ultra-high field imaging in areas suffering from static magnetic field inhomogeneities.

AB - OBJECTIVE: Signal drop-off occurs in echo-planar imaging in inferior brain areas due to field gradients from susceptibility differences between air and tissue. Tailored-RF pulses based on a hyperbolic secant (HS) have been shown to partially recover signal at 3 T, but have not been tested at higher fields.MATERIALS AND METHODS: The aim of this study was to compare the performance of an optimized tailored-RF gradient-echo echo-planar imaging (TRF GRE-EPI) sequence with standard GRE-EPI at 7 T, in a passive viewing of faces or objects fMRI paradigm in healthy subjects.RESULTS: Increased temporal-SNR (tSNR) was observed in the middle and inferior temporal lobes and orbitofrontal cortex of all subjects scanned, but elsewhere tSNR decreased relative to the standard acquisition. In the TRF GRE-EPI, increased functional signal was observed in the fusiform, lateral occipital cortex, and occipital pole, regions known to be part of the visual pathway involved in face-object perception.CONCLUSION: This work highlights the potential of TRF approaches at 7 T. Paired with a reversed-gradient distortion correction to compensate for in-plane susceptibility gradients, it provides an improved acquisition strategy for future neurocognitive studies at ultra-high field imaging in areas suffering from static magnetic field inhomogeneities.

KW - Journal Article

U2 - 10.1007/s10334-017-0652-x

DO - 10.1007/s10334-017-0652-x

M3 - Article

C2 - 28933028

SN - 0968-5243

JO - Magma: Magnetic Resonance Materials in Physics, Biology and Medicine

JF - Magma: Magnetic Resonance Materials in Physics, Biology and Medicine

ER -