Effects of eddy currents on selective spectral editing experiments at 3T
Georg Oeltzschner1,2, Karim Snoussi1,2, Nicolaas A Puts1,2
1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Journal of Magnetic Resonance Imaging : JMRI
|July 23, 2017
Summary
Magnetic resonance spectroscopy (MRS) eddy currents can significantly affect GABA-edited experiments. Optimizing crusher gradient orientation minimizes these frequency offsets, improving signal accuracy in clinical settings.
Area of Science:
- Magnetic Resonance Spectroscopy (MRS)
- Neuroimaging
- Biophysics
Background:
- Pulsed field gradients in Magnetic Resonance Spectroscopy (MRS) can induce B0 eddy currents.
- These eddy currents can cause frequency offsets, impacting spectral editing accuracy.
- Macromolecule-suppressed (MM-suppressed) gamma-aminobutyric acid (GABA)-edited experiments are particularly sensitive to frequency shifts.
Purpose of the Study:
- To investigate the impact of B0 eddy currents on frequency-offset effects in edited MRS.
- To quantify the relationship between gradient pulse orientation and eddy current-induced frequency shifts.
- To evaluate methods for mitigating these effects in GABA-edited MRS.
Main Methods:
- Performed macromolecule-suppressed (MM-suppressed) gamma-aminobutyric acid (GABA)-edited experiments at 3T.
- Utilized saturation-offset series of MEGA-PRESS experiments in phantoms.
- Quantified difference integrals and analyzed offset dependence to determine frequency differences (Δf).
Main Results:
- Frequency offset (Δf) varied significantly with voxel orientation due to gradient-related B0 eddy currents.
- Fixing the crusher-gradient coordinate-frame reduced orientation dependence of Δf to approximately 2 Hz.
- Water-suppression crusher gradients also introduced frequency offsets, impacting GABA signal detection.
Conclusions:
- Eddy currents from pulsed field gradients can significantly affect frequency-selective spectral-editing experiments like GABA-edited MRS.
- Careful selection of crusher gradient orientation is crucial for ameliorating these frequency offset effects.
- Optimizing gradient parameters can improve the accuracy of in vivo MRS GABA quantification.
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