Possible artifacts in dynamic CEST MRI due to motion and field alterations

Area of Science:

• Medical Imaging
• Biophysics
• Magnetic Resonance Imaging

Background:

• Dynamic CEST imaging, including dynamic glucose-enhanced (DGE) imaging, is a growing area of research.
• Observed CEST effects in tissue are typically small (0.5-2%), especially at clinical field strengths.
• Subtractive analysis of dynamic CEST data is susceptible to motion-induced artifacts.

Purpose of the Study:

• To investigate the impact of small motions and B0 shifts on dynamic CEST imaging.
• To quantify the magnitude of pseudo-CEST effects caused by artifacts.
• To highlight the necessity of motion correction in dynamic CEST studies.

Main Methods:

• Utilized a 3D-CEST baseline scan from a brain tumor patient at 3T.
• Simulated dynamic measurements by introducing artificial motion (0.6 mm translations) and B0 shifts (7 Hz).
• Analyzed the generated data to identify and characterize artifact patterns.

Main Results:

• Minor translations and B0 shifts generated pseudo-CEST effects around 1%.
• Artifact patterns were observed to be non-intuitive, particularly at tissue interfaces like CSF borders.
• These pseudo-effects can be erroneously interpreted as genuine dynamic agent uptake.

Conclusions:

• Correction or mitigation of small motions is critical for reliable dynamic CEST imaging.
• B0 alterations can also contribute to pseudo-CEST effects at 3T.
• Accurate interpretation of dynamic CEST data requires addressing motion and B0 artifacts, especially in patients with lesions.