Improved chemical exchange saturation transfer imaging with real-time frequency drift correction

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering

Background:

• Chemical Exchange Saturation Transfer (CEST) imaging is sensitive to B0 field fluctuations.
• B0 drift can lead to significant artifacts in quantitative CEST metrics like MTRasym and APTw.
• Real-time correction of B0 drift is crucial for reliable CEST imaging at 3T.

Purpose of the Study:

• To investigate the impact of frequency drift on 3T CEST imaging.
• To develop and validate a novel sequence for real-time B0 drift correction in CEST.
• To compare the performance of the new sequence against conventional methods.

Main Methods:

• A frequency-stabilized CEST (FS-CEST) sequence was developed by integrating a frequency stabilization module into a conventional non-frequency-stabilized CEST (NFS-CEST) sequence.
• The FS-CEST and NFS-CEST sequences were evaluated using an egg white phantom and 26 human subjects on a clinical MRI scanner.
• Key metrics assessed included z-spectrum, MTRasym spectrum, and APTw images.

Main Results:

• Uncorrected B0 drift caused significant over- or underestimation of APTw images and MTRasym spectra in both phantom and volunteer studies.
• The FS-CEST sequence demonstrated substantially improved stability in MTRasym spectra and APTw images compared to the NFS-CEST sequence.
• Quantitative analysis showed reduced variability in APTw signals from white matter regions with FS-CEST (-0.14% ± 0.37%) versus NFS-CEST (-0.32% ± 2.32%).

Conclusions:

• The proposed FS-CEST sequence effectively corrects B0 drift artifacts in real-time.
• This novel sequence enhances the stability and accuracy of CEST imaging without increasing scan time.
• FS-CEST is recommended for implementation on heavy-duty MRI scanners for improved quantitative CEST analysis.