Spin echo functional MRI in bilateral auditory cortices at 7T: An application of B1 shimming

Federico De Martino, Sebastian Schmitter, Michelle Moerel, Jinfeng Tian, Kamil Ugurbil, Elia Formisano, Essa Yacoub, Pierre Francois van de Moortele

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Ultra high fields (UHF) permit unprecedented explorations of functional organizations and insight into basic neuronal processes. Increases in the signal and contrast to noise ratios have allowed increases in the spatial resolution of T2* weighted gradient echo (GE) echo planar imaging (EPI). Furthermore, while the use of T2 weighted imaging methods at UHF (e.g. spin echo (SE) EPI, gradient and spin echo (GRASE) EPI) can also permit higher resolution images, they in addition allow for increased spatial specificity of functional responses, permitting the in-vivo study of functional organizations down to the columnar level of the cortex. The study of the visual cortex has, thus far, benefitted the most from higher resolution T2 weighted studies as achieving the required transmit B1 magnitude at 7T is more challenging in other brain regions, such as the auditory cortex. As such, auditory fMRI studies at UHF have been limited to T2* weighted GE sequences. Recent advances in multi-channel RF transmission (e.g. B1 shimming) have enabled procedures to efficiently address deficiencies in transmit B1 profiles. However, these techniques, shown to be advantageous in anatomical imaging at UHF, are not generally utilized to facilitate T2 weighted fMRI studies.Here we investigate the feasibility of applying B1 shimming to achieve efficient RF transmission in the human auditory cortex. We demonstrate that, with B1 shimming, functional responses to simple tones and to complex sounds (i.e. voices, speech, animal cries, tools and nature) can be efficiently measured with T2 weighted SE-EPI in the bilateral human auditory cortex at 7T without exceeding specific absorption rate (SAR) limits.

Original languageEnglish (US)
Pages (from-to)1313-1320
Number of pages8
JournalNeuroImage
Volume63
Issue number3
DOIs
StatePublished - Nov 15 2012

Keywords

  • 7T
  • Auditory cortex
  • B shimming
  • BOLD
  • FMRI
  • Spin echo

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