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Relaxation selective pulses in fast relaxing systems.

Christopher J Lopez1, Wei Lu1, Jamie D Walls1

  • 1Department of Chemistry, University of Miami, Coral Gables, FL 33124, United States.

Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|March 18, 2014
PubMed
Summary

This study optimized relaxation selective pulses (R^rsps) for sharper and more robust magnetization suppression. Optimized pulses enhance MRI applications like solvent suppression and are effective even with magnetic field variations.

Keywords:
GRAPE algorithmRelaxationSaturation profileSelective pulses

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Area of Science:

  • Magnetic Resonance Imaging
  • Pulse Sequence Design

Background:

  • Relaxation selective pulses (R^rsps) are crucial for suppressing specific magnetization signals in MRI.
  • Optimizing R^rsps enhances spectral selectivity and robustness against field inhomogeneities.

Purpose of the Study:

  • To optimize the selectivity and robustness of R^rsps for suppressing magnetization with specific relaxation times (T2=T2(rsp), T1=αT2).
  • To investigate the performance of frequency-swept hyperbolic secant and adiabatic time-optimal saturation pulses.

Main Methods:

  • Optimization of R^rsps for selectivity and robustness against B0 and B1 field inhomogeneities.
  • Experimental validation using aqueous solutions with varying [Mn(+2)] concentrations.
  • Analytical derivation of adiabatic time-optimal saturation pulses.

Main Results:

  • Optimized R^rsps demonstrated sharpened selectivity and robustness.
  • Frequency-swept hyperbolic secant and adiabatic pulses proved most effective.
  • Required pulse lengths were shorter than the inversion recovery delay (T1ln(2)).

Conclusions:

  • The optimized R^rsps are effective for selective saturation and solvent suppression in MRI.
  • The pulse design is robust to common magnetic field variations.
  • Further exploration of spin relaxation properties and adiabatic pulse derivations were conducted.