B₁ inhomogeneity corrected CEST MRI based on direct saturation removed omega plot model at 5T

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Quantitative Imaging

Background:

• Chemical Exchange Saturation Transfer (CEST) MRI visualizes macromolecules by detecting proton exchange with water.
• B1 field inhomogeneity is a significant challenge, hindering accurate CEST quantification.
• Existing correction methods are complex and often unreliable.

Purpose of the Study:

• To develop and validate a novel method for correcting B1 field inhomogeneity in CEST MRI.
• To improve the reliability and accuracy of quantitative CEST imaging, specifically for amide proton transfer (APT) effects.

Main Methods:

• A direct saturation (DS) removed omega plot model was proposed for B1 inhomogeneity correction.
• CEST imaging was performed on healthy volunteers at 5T under varying B1 field strengths.
• Amide proton transfer (APT) quantification was compared before and after correction using the proposed method and a conventional interpolation approach.

Main Results:

• The proposed method effectively mitigated artifacts caused by B1 inhomogeneity in APT images.
• Corrected APT maps exhibited more homogeneity with smaller standard deviations compared to uncorrected or interpolated maps.
• Correction using two or four CEST acquisitions yielded results comparable to using more acquisitions and superior to the interpolation method.

Conclusions:

• The novel DS-removed omega plot model provides reliable B1 inhomogeneity correction for CEST MRI.
• The method requires as few as two CEST acquisitions for effective correction.
• This approach significantly enhances the quantitative accuracy of CEST MRI.