Macroscopic susceptibility in ultra high field MRI

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biophysics

Background:

• Magnetic susceptibility is fundamental to MRI functionality and image quality.
• Understanding susceptibility artifacts is crucial for accurate interpretation of MRI data, particularly at ultra-high field strengths.

Purpose of the Study:

• To analyze magnetic susceptibility and its associated artifacts at 8 Tesla (T) in both phantoms and the human head.
• To investigate the impact of gradient-recalled echo (GRE) imaging on susceptibility artifacts.

Main Methods:

• Utilized a mineral oil phantom with air-filled tubes to simulate susceptibility variations.
• Acquired images using gradient-recalled echo (GRE) and spin-echo (SE) sequences with varying echo times (TE) and receiver bandwidths.
• Acquired near-axial, coronal, and sagittal GRE images from human volunteers at 8 T.

Main Results:

• GRE imaging produced significant magnetic susceptibility artifacts, clearly visible in phantom air-filled tubes.
• In the human head, artifacts caused substantial distortion and signal loss in the skull base region.
• Artifacts manifested as signal intensity bands in the frontal lobe/temporal bone, distorted brain vasculature, and accentuated venous structures.

Conclusions:

• Severe magnetic susceptibility artifacts occur at 8 T with GRE imaging and long echo times (TE).
• Increasing receiver bandwidths and decreasing effective TEs can mitigate these artifacts.
• Advancements in ultra-high field MRI susceptibility artifact management will benefit lower field strength studies.