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Prospective frequency correction using outer volume suppression-localized navigator for MR spectroscopy and
Chu-Yu Lee1, In-Young Choi1,2,3, Phil Lee1,3
1Hoglund Brain Imaging Center, University of Kansas Medical Center, Kansas City, Kansas.
Magnetic Resonance in Medicine
|May 15, 2018
Summary
A new outer volume suppression (OVS)-localized navigator prospectively corrects frequency drifts in magnetic resonance spectroscopy (MRS) and imaging (MRSI). This method improves data quality without impacting signal-to-noise ratio (SNR), crucial for accurate metabolite measurements.
Area of Science:
- Medical Imaging
- Spectroscopy
- Biophysics
Background:
- Accurate frequency measurements in Magnetic Resonance Spectroscopy (MRS) and Magnetic Resonance Spectroscopic Imaging (MRSI) are critical for reliable data analysis.
- Frequency drifts, caused by factors like head motion or hardware instability, can significantly degrade spectral quality and metabolite quantification.
- Existing frequency correction methods may have limitations in accuracy or impact on signal-to-noise ratio (SNR).
Purpose of the Study:
- To develop and validate a novel prospective frequency correction method for MRS and MRSI.
- To address the need for accurate measurement of frequency drifts in MRS and MRSI.
- To improve SNR and data quality compared to existing techniques.
Main Methods:
- A prospective frequency correction method utilizing outer volume suppression (OVS)-based localization and selective water excitation was developed.
- An OVS-localized navigator was implemented to prospectively correct frequency drifts during MRS and MRSI acquisition.
- The method was tested on human brain and phantom data, evaluating performance under motion-induced and gradient heating-induced frequency drifts at 3T.
Main Results:
- The OVS-localized navigator accurately tracked motion-induced frequency drifts with a Root Mean Square (RMS) error of 0.5 Hz.
- No significant SNR loss was observed with the OVS-localized navigator (P > 0.05).
- Prospective correction effectively recovered MRSI quality degraded by 5.1 ± 0.3 Hz/min frequency drifts from preceding DWI experiments, restoring spectral linewidth, metabolite concentrations, and Cramér-Rao lower bounds.
Conclusions:
- The OVS-localized navigator provides effective prospective frequency correction for substantial frequency drifts (up to 5 Hz/min).
- This technique achieves accurate frequency correction without inducing saturation-related SNR loss.
- The method is particularly advantageous for MRS acquisitions with long T1, short TR, and spectral editing applications.
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