Feasibility of strong diffusion encoding and fast readout using a plug-and-play head gradient insert at 7 T

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Physics

Background:

• Diffusion MRI signal acquisition is challenged by T2 relaxation, leading to signal decay.
• Conventional gradient strengths in diffusion MRI result in longer echo times (TE).
• Stronger gradients can shorten TE and enhance signal-to-noise ratio (SNR).

Purpose of the Study:

• To demonstrate the feasibility of using an ultrastrong head gradient insert for diffusion MRI at 7 Tesla (7T).
• To evaluate the impact of the gradient insert on echo time (TE) and signal-to-noise ratio (SNR).

Main Methods:

• A lightweight, single-axis gradient coil was integrated as a fourth gradient axis into a 7T MRI system.
• Diffusion MRI experiments compared acquisitions using the gradient insert at full capacity (200 mT/m, 1300 T/m/s) against conventional strengths (40-80 mT/m, 200 T/m/s).
• Acquisitions were performed for various b-values (0 to 10,000 s/mm²).

Main Results:

• The gradient insert enabled significantly shorter TEs (e.g., 28.8 ms vs. 59.9 ms at b=0) across all b-values.
• Acquisitions with the insert demonstrated an increased SNR compared to conventional methods.
• Using strong gradients for readout reduced TE by 20 ms and decreased geometrical distortions.

Conclusions:

• A successful proof-of-concept for diffusion MRI at 7T using a plug-and-play head gradient insert was achieved.
• The use of low-cost gradient inserts can potentially broaden the accessibility of advanced diffusion MRI techniques.
• This approach offers a pathway to improved diffusion-weighted imaging quality and reduced scan times.