Multi-echo-based fat artifact correction for CEST MRI at 7 T.

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Medical Physics

Background:

• Chemical Exchange Saturation Transfer (CEST) MRI is sensitive to fat signal interference, which can degrade image quality and lead to inaccurate results.
• Fat artifacts, including reduced contrast and pseudo-CEST effects, pose a significant challenge in high-field MRI, particularly at 7 Tesla (7T).

Purpose of the Study:

• To develop and validate a robust fat artifact correction method for 7T knee CEST MRI data.
• To address the limitations of existing fat suppression techniques by employing multi-echo fat-water separation.

Main Methods:

• A novel algorithm utilizing complex data and phase demodulation with off-resonance map estimation was developed for fat-water separation.
• The method was validated using Bloch-McConnell simulations, phantom measurements, and in vivo 7T knee MRI data.
• Performance was compared against multi-echo methods for 3T, Gaussian fat saturation, and a single-echo Z-spectrum-based correction method.

Main Results:

• The proposed method significantly reduced fat-water swaps and pseudo-nuclear Overhauser effects compared to existing techniques.
• Complex signal data processing yielded more stable correction results than magnitude data processing.
• Mean asymmetry contrast in cartilage improved from -9.2% (uncorrected) to -1.5%, demonstrating enhanced diagnostic potential.
• The technique exhibited superior spatial stability compared to fat saturation pulses.

Conclusions:

• Multi-echo fat-water separation with an adaptive fat model offers a feasible and effective solution for fat artifact correction in 7T CEST MRI.
• The developed approach provides superior fat artifact correction across the spectrum and imaging data compared to fat saturation and Z-spectrum-based methods.
• This advancement holds promise for improving the accuracy and reliability of 7T knee CEST MRI applications.