Parallel imaging with 3D TPI trajectory: SNR and acceleration benefits

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biomedical Engineering
• Radiology

Background:

• Three-dimensional (3D) twisted projection imaging (TPI) offers high signal-to-noise ratio (SNR) and short acquisition times for sodium ((23)Na) MRI on clinical scanners.
• Parallel imaging enhances MRI efficiency by undersampling k-space, leveraging coil element arrays to improve acquisition speed.
• Integrating parallel imaging with TPI trajectories is crucial for maximizing SNR and acceleration benefits in sodium imaging.

Purpose of the Study:

• To investigate the feasibility of parallel sodium imaging using the 3D TPI trajectory.
• To evaluate the signal-to-noise ratio (SNR) and acceleration benefits of TPI-SENSE.
• To assess noise amplification and image reconstruction accuracy in accelerated TPI-SENSE.

Main Methods:

• Computer simulations were conducted to determine achievable acceleration factors and noise amplification.
• Human head studies were performed on 1.5/3-T clinical MRI scanners using four-element coil arrays.
• The sensitivity encoding (SENSE) method with a conjugate gradient algorithm reconstructed images from accelerated TPI-SENSE data, utilizing self-calibration for coil sensitivities.

Main Results:

• An acceleration factor of up to 5.53 (2x3 ring-by-rotation) was achieved with a low image error of 6.9%.
• Average noise amplification was 98.7%, which is 27% lower than Cartesian SENSE at the same acceleration factor.
• The 3D nature of TPI and coil sensitivities likely contributes to high acceleration and reduced noise.

Conclusions:

• 3D TPI-SENSE demonstrates significant potential for accelerating sodium MRI acquisition.
• The method achieves high acceleration factors with minimal noise amplification compared to Cartesian SENSE.
• TPI-SENSE offers advantages for efficient and high-quality parallel sodium imaging on clinical MRI systems.