Abstract
IntroductionNeuroimaging of macaques at ultra-high field (UHF) is usually conducted by combining a volume coil for transmit (Tx) and a phased array coil for receive (Rx) tightly enclosing the monkey’s head. Good results have been achieved using vertical or horizontal magnets with implanted or near-surface coils. An alternative and less costly approach, the travelling-wave (TW) excitation concept, may offer more flexible experimental setups on human whole-body UHF magnetic resonance imaging (MRI) systems, which are now more widely available. Goal of the study was developing and validating the TW concept for in vivo primate MRI.MethodsThe TW Primate System (TWPS) uses the radio frequency shield of the gradient system of a human whole-body 7 T MRI system as a waveguide to propagate a circularly polarized B1 field represented by the TE11 mode. This mode is excited by a specifically designed 2-port patch antenna. For receive, a customized neuroimaging monkey head receive-only coil was designed. Field simulation was used for development and evaluation. Signal-to-noise ratio (SNR) was compared with data acquired with a conventional monkey volume head coil consisting of a homogeneous transmit coil and a 12-element receive coil.ResultsThe TWPS offered good image homogeneity in the volume-of-interest Turbo spin echo images exhibited a high contrast, allowing a clear depiction of the cerebral anatomy. As a prerequisite for functional MRI, whole brain ultrafast echo planar images were successfully acquired.ConclusionThe TWPS presents a promising new approach to fMRI of macaques for research groups with access to a horizontal UHF MRI system.
Highlights
OPEN ACCESSCitation: Herrmann T, Mallow J, Plaumann M, Luchtmann M, Stadler J, Mylius J, et al (2015) The Travelling-Wave Primate System: A New Solution for Magnetic Resonance Imaging of Macaque Monkeys at 7 Tesla Ultra-High Field
Good results have been shown by some research groups performing functional magnetic resonance imaging (fMRI) on monkeys using vertical ultra-high field (UHF) magnetics [2,3], with the advantage of lower acquisition costs and sitting monkey position but the disadvantage of limited space inside
magnetic resonance imaging (MRI) volume transmit radio frequency (RF) coils are not always suitable for fMRI on macaques because the RF coil tightly encloses their heads in order to generate a homogenous B1+ excitation, often limiting the number of necessary auditory or visual stimulation units that can be attached, which restricts some experimental setups
Summary
Academic Editor: Noam Harel, University of Minnesota, UNITED STATES. Neuroimaging of macaques at ultra-high field (UHF) is usually conducted by combining a volume coil for transmit (Tx) and a phased array coil for receive (Rx) tightly enclosing the monkey’s head. Good results have been achieved using vertical or horizontal magnets with implanted or near-surface coils. An alternative and less costly approach, the travellingwave (TW) excitation concept, may offer more flexible experimental setups on human whole-body UHF magnetic resonance imaging (MRI) systems, which are more widely available. Goal of the study was developing and validating the TW concept for in vivo primate MRI
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