Simultaneous multislice diffusion imaging using navigator-free multishot spiral acquisitions.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Diffusion Imaging
• Image Reconstruction

Background:

• Multiband (MB) imaging accelerates MRI by acquiring multiple slices simultaneously.
• Multishot diffusion imaging is crucial for high-resolution diffusion-weighted images but susceptible to phase errors.
• Uniform-density spiral (UDS) acquisition offers benefits for fast imaging but requires robust reconstruction.

Purpose of the Study:

• To develop a novel navigator-free multiband (MB) multishot uniform-density spiral (UDS) acquisition and reconstruction technique.
• To demonstrate the utility of this method for high-efficiency, high-resolution diffusion imaging.
• To address challenges in MB multishot UDS diffusion imaging, specifically phase variations and aliasing artifacts.

Main Methods:

• Radiofrequency-pulse encoding was employed for controlled aliasing in parallel imaging for MB acquisition.
• A novel reconstruction algorithm, slice-projection onto convex sets-enhanced inherent correction of phase errors (slice-POCS-ICE), was developed.
• The slice-POCS-ICE algorithm simultaneously estimates diffusion-weighted images and intershot phase variations for each slice.

Main Results:

• The slice-POCS-ICE algorithm demonstrated more precise estimation of phase variations compared to other methods in simulations and in vivo experiments.
• Improved image quality was achieved using the proposed slice-POCS-ICE method.
• Simultaneous resolution of intershot phase variations and MB slice aliasing artifacts was successfully accomplished.

Conclusions:

• The developed navigator-free MB multishot UDS acquisition and reconstruction method provides an effective solution for diffusion imaging.
• The technique enables high-efficiency and high-resolution diffusion imaging.
• The slice-POCS-ICE algorithm successfully mitigates artifacts, enhancing diffusion MRI capabilities.