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Correcting surface coil excitation inhomogeneities in single-shot SPEN MRI.

  • Schmidt R Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel.
  • Mishkovsky M Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
  • Hyacinthe JN School of health, University of Applied Sciences and Arts Western Switzerland, Geneva, Switzerland.
  • Kunz N Center of Biomedical Imaging (CIBM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
  • Gruetter R Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
  • Comment A Institute of the Physics of Biological Systems, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
  • Frydman L Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel.
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  • 2015-09-14
Published in:
  • Journal of magnetic resonance (San Diego, Calif. : 1997). - 2015
B(1) corrections
Spatiotemporal encoding
Surface coil MRI
Swept pulses
Ultrafast MRI
Algorithms
Animals
Brain
Echo-Planar Imaging
Electromagnetic Fields
Magnetic Resonance Imaging
Magnetic Resonance Spectroscopy
Phantoms, Imaging
Radio Waves
Rats
English Given their high sensitivity and ability to limit the field of view (FOV), surface coils are often used in magnetic resonance spectroscopy (MRS) and imaging (MRI). A major downside of surface coils is their inherent radiofrequency (RF) B1 heterogeneity across the FOV, decreasing with increasing distance from the coil and giving rise to image distortions due to non-uniform spatial responses. A robust way to compensate for B1 inhomogeneities is to employ adiabatic inversion pulses, yet these are not well adapted to all imaging sequences - including to single-shot approaches like echo planar imaging (EPI). Hybrid spatiotemporal encoding (SPEN) sequences relying on frequency-swept pulses provide another ultrafast MRI alternative, that could help solve this problem thanks to their built-in heterogeneous spatial manipulations. This study explores how this intrinsic SPEN-based spatial discrimination, could be used to compensate for the B1 inhomogeneities inherent to surface coils. Experiments carried out in both phantoms and in vivo rat brains demonstrate that, by suitably modulating the amplitude of a SPEN chirp pulse that progressively excites the spins in a direction normal to the coil, it is possible to compensate for the RF transmit inhomogeneities and thus improve sensitivity and image fidelity.
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  • English
Open access status
green
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Persistent URL
https://folia.unifr.ch/global/documents/69711
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