Low-distortion diffusion tensor MRI with improved phaseless encoding.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Imaging Physics
• Diffusion Tensor Imaging (DTI)

Background:

• Single-shot diffusion MRI techniques like echo-planar imaging (EPI) are limited by resolution and distortions.
• Multi-shot methods require navigators or sensitivity encoding trade-offs to correct phase errors.

Purpose of the Study:

• To apply and evaluate phaseless encoding for routine diffusion tensor imaging (DTI) at moderately high resolution.
• To compare phaseless encoding with single-shot EPI and navigator-based readout-segmented EPI regarding image distortions.

Main Methods:

• Phaseless encoding utilizes image magnitude from multiple shots, analogous to optical super-resolution, to eliminate phase errors.
• Technical improvements include slice-selective tagging pulses, optimized flip angles, and enhanced super-resolution reconstruction algorithms.
• Comparison with single-shot EPI and readout-segmented EPI was performed on a standard 3T scanner.

Main Results:

• Phaseless encoding produced less distorted diffusion-weighted images than single-shot EPI at equivalent resolution and hardware parameters.
• Qualitative comparison showed comparable results to navigator-based readout-segmented EPI.
• Proposed improvements enhance compatibility with routine multi-slice scanning.

Conclusions:

• Phaseless encoding is a promising diffusion-weighted imaging technique with reduced distortions compared to single-shot EPI.
• It offers comparable performance to navigator-based methods without the need for navigators.
• The technique is suitable for routine DTI protocols and multi-slice acquisitions.