Localized, gradient-reversed ultrafast z-spectroscopy in vivo at 7T.
Neil E Wilson, Kevin D'Aquilla, Catherine Debrosse, Hari Hariharan, Ravinder Reddy
Author Information
- Neil E Wilson: Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Phildelphia PA.
- Kevin D'Aquilla: Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Phildelphia PA.
- Catherine Debrosse: Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Phildelphia PA.
- Hari Hariharan: Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Phildelphia PA.
- Ravinder Reddy: Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Phildelphia PA.
PURPOSE: To collect ultrafast z-spectra in vivo in situations where voxel homogeneity cannot be assured.
THEORY: Saturating in the presence of a gradient encodes the frequency offset spatially across a voxel. This encoding can be resolved by applying a similar gradient during readout. Acquiring additional scans with the gradient polarity reversed effectively mirrors the spatial locations of the frequency offsets so that the same physical location of a positive offset in the original scan will contribute a negative offset in the gradient-reversed scan.
METHODS: Gradient-reversed ultrafast z-spectroscopy (GRUFZS) was implemented and tested in a modified, localized PRESS sequence at 7T. Lysine phantoms were scanned at various concentrations and compared with coventionally-acquired z-spectra. Scans were acquired in vivo in human brain from homogeneous and inhomogeneous voxels with the ultrafast direction cycled between read, phase, and slice. Results were compared to those from a similar conventional z-spectroscopy PRESS-based sequence.
RESULTS: Asymmetry spectra from GRUFZS are more consistent and reliable than those without gradient reversal and are comparable to those from conventional z-spectroscopy. GRUFZS offers significant acceleration in data acquisition compared to traditional chemical exchange saturation transfer methods with high spectral resolution and showed higher relative SNR effficiency.
CONCLUSION: GRUFZS offers a method of collecting ultrafast z-spectra in voxels with the inhomogeneity often found in vivo. Magn Reson Med 76:1039-1046, 2016. © 2016 Wiley Periodicals, Inc.
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- P41 EB015893/NIBIB NIH HHS
- R01 NS087516/NINDS NIH HHS
- T32 EB020087/NIBIB NIH HHS
Algorithms
Brain
Humans
Lysine
Magnetic Resonance Imaging
Magnetic Resonance Spectroscopy
Molecular Imaging
Phantoms, Imaging
Reproducibility of Results
Sensitivity and Specificity
Signal Processing, Computer-Assisted
Tissue Distribution
