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Gradient-modulated SWIFT.

Jinjin Zhang1,2, Djaudat Idiyatullin1, Curtis A Corum1

  • 1Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.

Magnetic Resonance in Medicine
|March 25, 2015
PubMed
Summary
This summary is machine-generated.

Gradient-modulated gradient-modulation with fast imaging (GM-SWIFT) reduces specific absorption rate (SAR) and scan time for MRI. This technique enhances imaging flexibility and quality while lowering RF power demands.

Keywords:
GOIASARSWIFTVERSEfast relaxing spinsfrequency sweepgradient modulationultrashort T2

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Area of Science:

  • Magnetic Resonance Imaging (MRI)
  • Pulse Sequence Design

Background:

  • Sweep imaging with Fourier transformation (SWIFT) is crucial for imaging fast-relaxing spins.
  • High excitation bandwidth and duty cycles in SWIFT can lead to exceeding safe specific absorption rate (SAR) limits.
  • Optimal flip angles are often unattainable in SWIFT due to SAR constraints.

Purpose of the Study:

  • To reduce SAR and enhance the flexibility of SWIFT.
  • To introduce a modified SWIFT sequence named GM-SWIFT (gradient-modulated SWIFT).
  • To achieve these goals by applying time-varying gradient modulation (GM).

Main Methods:

  • Utilized gradient-modulated offset independent adiabaticity for radiofrequency (RF) pulse and gradient modulation.
  • Developed an expanded correlation algorithm to correct phase and scale effects in GM-SWIFT.
  • Validated the algorithm and evaluated imaging performance through simulations, phantom studies, and in vivo human experiments.

Main Results:

  • GM-SWIFT achieved reductions of up to 90% in SAR, 70% in RF amplitude, and 45% in acquisition time.
  • Image quality was maintained despite significant reductions in SAR and acquisition time.
  • The GM parameter tuning allowed for suppression of image haze from ultrashort T2 (*) signals.

Conclusions:

  • GM-SWIFT effectively lowers peak and total RF power requirements.
  • The technique offers enhanced flexibility for optimizing SAR, RF amplitude, scan time, and overall image quality.
  • GM-SWIFT presents a valuable advancement for MRI pulse sequence development.