4D flow imaging with 2D-selective excitation.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Cardiovascular Flow Dynamics
• Medical Imaging Physics

Background:

• 4D flow MRI enables non-invasive quantification of time-dependent velocity vector fields.
• Current 4D flow MRI methods require lengthy acquisition times, limiting clinical applicability.
• 2D-selective excitation offers a potential solution to accelerate MRI acquisition by reducing the field of view (FOV).

Purpose of the Study:

• To investigate the efficacy of 2D-selective excitation with reduced FOV imaging for accelerating 4D flow MRI.
• To assess the accuracy of velocity quantification using this accelerated technique.
• To determine if reduced FOV imaging preserves the integrity of velocity measurements in 4D flow MRI.

Main Methods:

• Designed two 2D-selective excitation pulses utilizing spiral k-space trajectories.
• Analyzed the isophase time point of these pulses via simulations with stationary and moving spins.
• Implemented the 2D-selective pulses into a 4D flow sequence and validated with flow phantom and in vivo studies.

Main Results:

• The isophase time point for spiral 2D-selective RF pulses was identified at the end of excitation.
• Reduced FOV 2D-selective excitation successfully quantified velocities in phantom and in vivo scans.
• Phantom velocity differences were comparable to inter-scan variability; in vivo flow and flow volume differences were non-significant.
• Reducing FOV by two-thirds halved the acquisition time.

Conclusions:

• Reduced field-of-excitation in 4D flow MRI effectively shortens acquisition times.
• This method preserves accurate velocity quantification, making 4D flow MRI more efficient.
• 2D-selective excitation with reduced FOV is a viable strategy for faster 4D flow imaging.