Effects of polar sampling in k-space

Area of Science:

• Medical Imaging
• Physics

Background:

• Magnetic resonance imaging (MRI) employs various k-space sampling schemes, including rectilinear and non-rectilinear trajectories.
• Non-rectilinear acquisitions offer advantages like faster scan times and motion artifact suppression.
• However, these schemes can introduce aliasing, negatively impacting image quality.

Purpose of the Study:

• To explain the Fourier aliasing effects specific to uniform polar k-space sampling in MRI.
• To characterize the radial effects of this sampling method using the principal point spread function (PSF).

Main Methods:

• Analysis of Fourier aliasing effects based on the principal point spread function (PSF).
• Determination of the PSF assuming equally spaced concentric ring samples in k-space.
• Characterization of radial effects including replication, smearing, and truncation artifacts.

Main Results:

• Uniform polar sampling leads to specific Fourier aliasing patterns.
• The PSF analysis reveals replication and smearing artifacts due to radial sampling.
• Truncation artifacts are also identified and characterized based on the PSF.

Conclusions:

• Understanding aliasing from uniform polar sampling is crucial for MRI image quality.
• The PSF provides a framework for characterizing and potentially mitigating these artifacts.
• This analysis informs sampling requirements for improved non-rectilinear MR acquisitions.