Single shot fast spin echo diffusion imaging with correction for non-linear phase errors using tailored RF pulses.

Area of Science:

• Magnetic Resonance Imaging
• Neuroimaging
• Biophysics

Background:

• Echo-planar imaging (EPI) is standard for diffusion-weighted (DW) imaging but sensitive to magnetic field inhomogeneities and motion.
• Fast spin echo (FSE) sequences are less sensitive to field inhomogeneities but struggle with motion-induced phase shifts, especially non-linear patterns from pulsatile motion.

Purpose of the Study:

• To enable in vivo diffusion-weighted (DW) fast spin echo (FSE) imaging using tailored radiofrequency (RF) excitation pulses for prospective correction of non-linear motion-induced phase patterns.
• To overcome the limitations of existing DW imaging techniques regarding motion artifacts and field inhomogeneities.

Main Methods:

• Calibration of reproducible non-linear phase components using 2D-EPI navigators.
• Design of tailored RF excitation pulses for real-time phase correction.
• Acquisition of full signal DW-FSE images and diffusion tensor data.

Main Results:

• Successful phase correction demonstrated with full signal DW-FSE images in cooperative subjects.
• Acquisition of complete diffusion tensor data and calculation of principal fiber directionality maps.
• DW-FSE results showed consistency with EPI acquisitions, notably without spatial distortions.

Conclusions:

• The proposed method, when combined with real-time rigid-body motion compensation, has the potential to provide high-quality, distortion-free diffusion imaging of the brain.
• This approach offers an alternative to EPI for DW imaging, improving spatial accuracy.