Two-point B₁ correction for CEST MRI by fusing voxel-wise interpolation and T₁W voxel-clustering

Area of Science:

• Magnetic Resonance Imaging
• Metabolic Imaging
• Biomedical Engineering

Background:

• Chemical Exchange Saturation Transfer (CEST) MRI is sensitive but prone to B1 inhomogeneity.
• B1 inhomogeneity significantly impacts CEST image quality due to dependence on saturation B1.

Purpose of the Study:

• To develop an efficient and robust two-point B1-correction method for CEST MRI.
• To mitigate artifacts caused by B1 inhomogeneity in CEST imaging.

Main Methods:

• Acquired CEST images using two saturation B1 levels (B1,high and B1,low).
• Employed voxel-wise Z-B1 interpolation (Branch A) and Z-T1-B1 calibration (Branch B).
• Fused corrected images from both branches using a mask predicted by a trained model.

Main Results:

• Branch B achieved mean absolute error (MAE) of Z(3ppm) ≤ 5% across 42 experiments on glutamate phantoms.
• For healthy volunteers, Branch B results closely matched 7-B1 correction with robust MAE distributions.
• Fused images showed improved structural similarity index measure (SSIM) compared to individually corrected branches.

Conclusions:

• The two-point B1-correction strategy demonstrated comparable performance to multi-B1 methods.
• The method is robust to B1 selection and slice positions.
• This technique offers an efficient way to improve CEST MRI accuracy.