3D variable-density SPARKLING trajectories for high-resolution T2*-weighted magnetic resonance imaging

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biomedical Engineering
• Image Reconstruction

Background:

• Conventional non-Cartesian MRI trajectories like radial lines and spirals have limitations in k-space sampling density and gradient waveform optimization.
• Efficient k-space sampling is crucial for reducing MRI scan times and improving image quality.

Purpose of the Study:

• To extend the SPARKLING (Spreading Projection Algorithm for Rapid K-space sampLING) method for 3D MRI acquisition.
• To evaluate the performance of 3D SPARKLING trajectories in terms of speed, resolution, and artifact reduction.

Main Methods:

• The study introduces extensions of the SPARKLING algorithm for 3D imaging, including stacks-of-SPARKLING and fully 3D SPARKLING trajectories.
• The proposed method optimizes gradient waveforms and allows arbitrary k-space density sampling.
• Ex vivo and in vivo human brain imaging data were acquired at 7 Tesla.

Main Results:

• Achieved an isotropic resolution of 600 μm in 45 seconds for ex vivo T2*-weighted brain imaging over a 200 × 200 × 140 mm³ field-of-view.
• Preliminary in vivo human brain data demonstrated that stack-of-SPARKLING trajectories are less susceptible to off-resonance artifacts compared to stack-of-spirals.

Conclusions:

• The extended SPARKLING method enables highly efficient 3D k-space sampling for accelerated MRI.
• SPARKLING trajectories offer advantages over conventional methods, including flexible density sampling and optimized gradient waveforms.
• The technique shows promise for reducing scan times and improving image quality in clinical MRI applications, particularly in challenging scenarios like in vivo human brain imaging.