title: Dense, shape-optimized posterior 32-channel coil for submillimeter functional imaging of visual cortex at 3T.
abstract: Functional neuroimaging of small cortical patches such as columns is essential for testing computational models of vision, but imaging from cortical columns at conventional 3T fields is exceedingly difficult. By targeting the visual cortex exclusively, we tested whether combined optimization of shape, coil placement, and electronics would yield the necessary gains in signal-to-noise ratio (SNR) for submillimeter visual cortex functional MRI (fMRI).
  
  
  
  We optimized the shape of the housing to a population-averaged atlas. The shape was comfortable without cushions and resulted in the maximally proximal placement of the coil elements. By using small wire loops with the least number of solder joints, we were able to maximize the Q factor of the individual elements. Finally, by planning the placement of the coils using the brain atlas, we were able to target the arrangement of the coil elements to the extent of the visual cortex.
  
  
  
  The combined optimizations led to as much as two-fold SNR gain compared with a whole-head 32-channel coil. This gain was reflected in temporal SNR as well and enabled fMRI mapping at 0.75 mm resolutions using a conventional GRAPPA-accelerated gradient echo echo planar imaging.
  
  
  
  Integrated optimization of shape, electronics, and element placement can lead to large gains in SNR and empower submillimeter fMRI at 3T. Magn Reson Med 76:321-328, 2016. © 2015 Wiley Periodicals, Inc.
authors.affiliation: McGill Vision Research Unit, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada.
authors.forename: Reza
authors.initials: R
authors.lastname: Farivar
authors.affiliation: McGill Vision Research Unit, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada.
authors.forename: Filip
authors.initials: F
authors.lastname: Grigorov
authors.affiliation: A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, USA.|Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Andre J
authors.initials: AJ
authors.lastname: van der Kouwe
authors.affiliation: A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, USA.|Harvard Medical School, Boston, Massachusetts, USA.|Health Science and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Wald
authors.affiliation: A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, USA.|Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Boris
authors.initials: B
authors.lastname: Keil
mesh_terms: D001931:Brain Mapping / Q000295:instrumentation*; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005074:Evoked Potentials, Visual / Q000502:physiology*; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008280:Magnetics / Q000295:instrumentation*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D014793:Visual Cortex / Q000502:physiology*
keywords: accelerated EPI; fMRI; functional MRI; magnetic resonance imaging; ocular dominance columns; orientation columns; parallel imaging; phased-array; shape optimization