Imaging brain function in humans at 7 Tesla

Abstract

This article describes experimental studies performed to demonstrate the feasibility of BOLD fMRI using echo-planar imaging (EPI) at 7 T and to characterize the BOLD response in humans at this ultrahigh magnetic field. Visual stimulation studies were performed in normal subjects using high-resolution multishot EPI sequences. Changes in R* 2 arising from visual stimulation were experimentally determined using fMRI measurements obtained at multiple echo times. The results obtained at 7 T were compared to those at 4 T. Experimental data indicate that fMRI can be reliably performed at 7 T and that at this field strength both the sensitivity and spatial specificity of the BOLD response are increased. This study suggests that ultrahigh field MR systems are advantageous for functional mapping in humans. Magn Reson Med 45:588 -594, 2001.

Where sound position influences sound object representations: A 7-T fMRI study

“…5). The combination of the high spatial resolution of the fMRI data, increased BOLD sensitivity and specificity available from higher field strengths Turner et al, 1993;van der Zwaag et al, 2009a,b;Yacoub et al, 2001) in combination with a wavelet-based analysis (Van De Ville et al, 2007;Van De Ville and Unser, 2008) of the functional images avoided a reduction of the spatial resolution. As a result, the distinction between the primary and non-primary auditory areas in fMRI data was possible and the used spatial resolution was sufficient to distinguish between areas which were sensitive to differences in presented sound location and those which were not.…”

“…Or, in other words, ultra-high fields facilitate image acquisition with significantly higher spatial resolution than possible at lower field strengths (Yacoub et al, 2001. The available BOLD, Blood Oxygenation Level Dependent, signal on which fMRI experiments are based, also increases with field strength, yielding even higher sensitivity (van der Zwaag et al, 2009a;Yacoub et al, 2001).…”

“…Or, in other words, ultra-high fields facilitate image acquisition with significantly higher spatial resolution than possible at lower field strengths (Yacoub et al, 2001. The available BOLD, Blood Oxygenation Level Dependent, signal on which fMRI experiments are based, also increases with field strength, yielding even higher sensitivity (van der Zwaag et al, 2009a;Yacoub et al, 2001). Finally, the signal strength of venous blood is reduced due to a shorter relaxation time, so that spatial specificity of the BOLD signal is improved, yielding activation signals which are restricted to the cortical grey matter van der Zwaag et al, 2009a,b).…”

Physiological noise in human cerebellar fMRI

“…Because of its relatively small size and fine-scale anatomical structure, compared to the cerebrum, cerebellar fMRI benefits strongly from high spatial resolution, both during acquisition [1,2] and in data post-processing strategies used in fMRI [3,4]. High spatial resolution in fMRI is most easily achieved at high field strengths, where fMRI benefits from increased signal-tonoise ratio (SNR), increased blood oxygen level-dependent (BOLD) signal [5,6] and increased spatial specificity of the BOLD responses [7,8].…”

SAR and power implications of different RF shimming strategies in the pelvis for 7T MRI

“…THE INCREASE in main magnetic field strength for human magnetic resonance imaging (MRI) toward 7 T has shown large benefits for head imaging, where the higher signal-to-noise ratio can be used to increase scan speed and/or to obtain a higher resolution (1)(2)(3)(4) and where the higher spectral resolution (5,6) and the increased sensitivity for various contrast mechanisms such as blood oxygenation level-dependent (BOLD) (4,7,8) have proven useful.…”