Nyquist ghost elimination for diffusion MRI by dual-polarity readout at low b-values

Area of Science:

• Magnetic Resonance Imaging
• Diffusion MRI

Background:

• Nyquist ghosting is a common artifact in diffusion-weighted echo-planar imaging.
• Dual-polarity readout effectively mitigates this artifact but typically doubles scan time.

Purpose of the Study:

• To propose a method for implementing dual-polarity readout with minimal or no increase in scan time.
• To exploit b-value dependence and signal averaging for ghosting reduction.

Main Methods:

• Investigated b-value dependence of ghosting in healthy volunteers.
• Applied dual-polarity readout strategy to tensor-valued diffusion encoding scans.
• Evaluated ghosting in parameter maps of mean diffusivity and kurtosis.

Main Results:

• Distinct ghosting was observed at low b-values, diminishing at b=1000 s/mm^2.
• Ghosting artifacts propagated into mean diffusivity and kurtosis maps without dual-polarity readout.
• The proposed strategy effectively eliminated ghosting without extending scan time.

Conclusions:

• Extending dual-polarity readout to low non-zero b-values offers effective ghost elimination.
• This approach can be integrated into diffusion MRI scans with signal averaging without increasing scan duration.
• The method is applicable to various diffusion MRI sequences, including those for tensor-valued encoding.