Using multi-echo simultaneous multi-slice (SMS) EPI to improve functional MRI of the subcortical nuclei of the basal ganglia at ultra-high field (7T)

Alexander M Puckett, Saskia Bollmann, Benedikt A Poser, Jake Palmer, Markus Barth, Ross Cunnington

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The nuclei of the basal ganglia pose a special problem for functional MRI, especially at ultra-high field, because T2* variations between different regions result in suboptimal BOLD sensitivity when using gradient-echo echo-planar imaging (EPI). Specifically, the iron-rich lentiform nucleus of the basal ganglia, including the putamen and globus pallidus, suffers from substantial signal loss when imaging is performed using conventional single-echo EPI with echo times (TE) optimized for the cortex. Multi-echo EPI acquires several echoes at different echo times for every imaging slice, allowing images to be reconstructed with a weighting of echo times that is optimized individually for each voxel according to the underlying tissue or T2* properties. Here we show that multi-echo simultaneous multi-slice (SMS) EPI can improve functional activation of iron-rich subcortical regions while maintaining sensitivity within cortical areas. Functional imaging during a motor task known to elicit strong activations in the cortex and the subcortex (basal ganglia) was performed to compare the performance of multi-echo SMS EPI to single-echo SMS EPI. Notably within both the caudate nucleus and putamen of the basal ganglia, multi-echo SMS EPI yielded higher tSNR (an average 84% increase) and CNR (an average 58% increase), an approximate 3-fold increase in supra-threshold voxels, and higher t-values (an average 39% increase). The degree of improvement in the group level t-statistics was negatively correlated to the underlying T2* of the voxels, such that the shorter the T2*, as in the iron-rich nuclei of the basal ganglia, the higher the improvement of t-values in the activated region.

Original languageEnglish
Pages (from-to)886-895
Number of pages10
JournalNeuroimage
Volume172
Early online date5 Dec 2017
DOIs
Publication statusPublished - 15 May 2018

Keywords

  • Journal Article
  • TRANSVERSE RELAXATION RATES
  • SINGLE-SHOT
  • HUMAN BRAIN
  • Motor
  • Susceptibility artifacts
  • 3 T
  • IRON CONTENT
  • CORTEX
  • SEGMENTED EPI
  • Signal loss
  • Echo time
  • PHYSIOLOGICAL NOISE
  • Functional MRI
  • BOLD-CONTRAST SENSITIVITY
  • Simultaneous multi-slice
  • Multi-echo
  • TASK FMRI
  • EPI
  • Echo-Planar Imaging/methods
  • Humans
  • Magnetic Resonance Imaging/methods
  • Male
  • Young Adult
  • Adult
  • Female
  • Brain Mapping/methods
  • Basal Ganglia/diagnostic imaging

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