Effects of gradient anisotropy in MRI

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Physics

Background:

• Anisotropic gradient systems occur when gradient channels (x, y, z) have differing impulse responses.
• Causes include eddy currents and electronic time delays, leading to deviations from nominal gradients.

Purpose of the Study:

• To theoretically analyze the effects of gradient system anisotropy in MRI.
• To describe implications for the MRI process and explore potential correction strategies.

Main Methods:

• Theoretical analysis of gradient system anisotropy.
• Experimental validation using echo-planar imaging and spiral gradient pulses.
• Investigation of 2D selective RF excitation.

Main Results:

• Anisotropy causes deviations in actual gradients from desired ones during transient switching periods.
• Observed image quality degradation, including distortion, ghosting, and blurring.
• Experimental demonstration of anisotropy effects in specific MRI sequences.

Conclusions:

• Gradient system anisotropy is a significant factor impacting MRI image quality.
• Understanding and correcting anisotropy is crucial for accurate MRI.
• Proposed methods aim to mitigate adverse effects and enhance diagnostic utility.