Advances in real-time phase-contrast flow MRI using asymmetric radial gradient echoes

Area of Science:

• Magnetic Resonance Imaging
• Cardiovascular Imaging
• Medical Physics

Background:

• Real-time phase-contrast MRI is crucial for assessing cardiovascular dynamics.
• Current methods face limitations in temporal resolution and velocity compensation.
• Undersampling techniques are essential for achieving real-time imaging.

Purpose of the Study:

• To develop and validate a novel method for multidimensional velocity compensation in real-time phase-contrast flow MRI.
• To enhance temporal resolution and minimize artifacts in flow imaging.

Main Methods:

• Implementation of asymmetric gradient echoes in highly undersampled radial FLASH MRI.
• Phase-sensitive image reconstruction using regularized nonlinear inversion (NLINV).
• Adaptation of gradient delay correction and incorporation of velocity-compensating waveforms.

Main Results:

• Demonstrated a usable asymmetry of 20% with improved image quality.
• Achieved full velocity compensation, eliminating signal void in flow phantoms.
• Validated in vivo performance in healthy subjects and patients, showing signal recovery and phase conservation.

Conclusions:

• Asymmetric gradient echoes enable highly undersampled radial trajectories for real-time flow MRI.
• The temporal gain allows for full velocity compensation, reducing false positives from complex flow.
• This method enhances temporal resolution compared to symmetric echo acquisitions.