Improved gradient-echo 3D magnetic resonance imaging using compressed sensing and Toeplitz encoding with...

Area of Science:

• Medical Imaging
• Biophysics
• Signal Processing

Background:

• Conventional magnetic resonance imaging (MRI) faces limitations in achieving high resolution and signal-to-noise ratio (SNR) simultaneously.
• Compressed sensing (CS) and non-Fourier encoding techniques offer potential solutions for accelerated MRI acquisition.
• Optimizing radio-frequency (RF) pulse design is crucial for improving MRI performance and reducing power deposition.

Purpose of the Study:

• To develop a novel three-dimensional (3D) hybrid-encoding framework combining compressed sensing (CS) and Toeplitz encoding with phase-scrambled RF excitation.
• To leverage advantages such as low RF power deposition, reduced signal dynamic range, and improved SNR without requiring additional hardware.
• To enhance image detail preservation and acquisition speed in 3D MRI.

Main Methods:

• Implementation of a 3D hybrid Fourier-Toeplitz encoding method using a gradient-recalled echo (GRASS) sequence with specially tailored RF pulses.
• Exploitation of Toeplitz encoding along the phase encoding direction, while maintaining Fourier encoding for readout and slice encoding.
• Optimization of RF pulse amplitudes through phantom experiments, followed by in vivo validation and comparative simulations against conventional and other non-Fourier encoding methods.

Main Results:

• Optimized low RF amplitude achieved in phantom experiments.
• Demonstrated superior image detail preservation compared to conventional 3D Fourier encoding at acceleration factors of 3.1 and 2.0 in watermelon and knee imaging.
• Reported improved SNR due to 3D volume encoding and absence of additional gradients, outperforming single-slice scanning.
• Simulations confirmed the proposed method's superiority over conventional Fourier encoding and comparable performance to other non-Fourier methods in detail preservation.

Conclusions:

• A practical hybrid-encoding method for 3D MRI was successfully developed using phase-scrambled RF excitation.
• The proposed method significantly improves image SNR and detail preservation compared to conventional Fourier encoding techniques.
• The novel approach offers superior performance in preserving image details, making it a promising advancement in 3D MRI.