Echo planar time-resolved imaging with subspace reconstruction and optimized spatiotemporal encoding.

Area of Science:

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

Background:

• Echo Planar Time-resolved Imaging (EPTI) enables fast, distortion-free multi-contrast and quantitative imaging.
• Improving reconstruction accuracy at high acceleration factors is crucial for EPTI's clinical utility.

Purpose of the Study:

• To develop advanced encoding and reconstruction techniques for accelerated multi-contrast and quantitative MRI.
• To enhance the performance of EPTI, particularly at high acceleration rates.

Main Methods:

• A subspace reconstruction framework was developed, modeling temporal signal evolution with low-rank subspace to reduce unknowns.
• A B0-update algorithm and shot-to-shot B0 variation correction were implemented for high-resolution phase imaging.
• The EPTI technique was extended to 3D k-space (3D GE-EPTI) with a novel temporal-variant CAIPI encoding scheme.

Main Results:

• Subspace reconstruction demonstrated superior accuracy compared to conventional B0-informed GRAPPA in 2D GESE EPTI.
• 3D GE-EPTI with temporal-variant CAIPI achieved up to 72x acceleration with reduced reconstruction error.
• High-quality whole-brain quantitative and tissue phase maps at 1 mm isotropic resolution were acquired in 52 seconds.

Conclusions:

• The proposed subspace reconstruction significantly improves EPTI accuracy at high accelerations.
• Optimized temporal-variant CAIPI encoding further enhances EPTI performance for rapid quantitative mapping.
• These advancements enable faster and more precise quantitative MRI.