PRIME: Phase Reversed Interleaved Multi-Echo acquisition enables highly accelerated distortion-free diffusion MRI.

Area of Science:

• Magnetic Resonance Imaging
• Neuroimaging
• Biomedical Engineering

Background:

• Diffusion MRI (dMRI) is crucial for neuroimaging but often limited by scan time and image distortions.
• Accelerated acquisition techniques are needed to improve dMRI efficiency and resolution.
• Generalized slice dithered enhanced resolution (gSlider) enables volumetric dMRI but requires robust methods for acceleration.

Purpose of the Study:

• To develop and validate a novel pulse sequence for highly accelerated, distortion-free dMRI.
• To integrate an additional echo into the acquisition without extending the repetition time (TR).
• To leverage gSlider encoding for efficient volumetric dMRI acquisition.

Main Methods:

• Developed the phase-reversed interleaved multi-echo acquisition (PRIME) sequence.
• PRIME incorporates two echoes: one for high-resolution diffusion-weighted imaging (DWI) and a second for field map estimation or diffusion relaxometry.
• Evaluated PRIME in vivo on healthy volunteers using clinical and Connectome 2.0 scanners.

Main Results:

• Achieved 5-fold in-plane acceleration using high-fidelity field maps from a lower-resolution second echo.
• Enabled high-resolution diffusion relaxometry parameter estimation using dual-echo PRIME data.
• Demonstrated in vivo high-fidelity mesoscale DWI at 550 µm isotropic resolution on the Connectome 2.0 scanner.

Conclusions:

• The PRIME sequence facilitates highly accelerated, high-resolution, and distortion-free dMRI.
• The integration of an additional echo without prolonging scan time is a key innovation.
• PRIME effectively utilizes gSlider encoding for advanced dMRI applications.