Real-time multi-directional flow MRI using model-based reconstructions of undersampled radial FLASH - A feasibility...

Area of Science:

• Medical Imaging
• Cardiovascular MRI
• Fluid Dynamics

Background:

• Current MRI techniques for blood flow often rely on ECG gating, which can combine data from multiple heartbeats.
• Real-time MRI for one-directional flow exists but lacks multi-directional capabilities.

Purpose of the Study:

• To develop a real-time acquisition and reconstruction technique for two- and three-directional (2D and 3D) phase-contrast flow MRI.
• To extend existing real-time MRI methods to capture in-plane flow in addition to through-plane flow.

Main Methods:

• Utilized highly undersampled radial FLASH sequences with sequential acquisitions for flow-encoding and flow-compensated datasets.
• Minimized echo times by merging flow-encoding and radial imaging gradient waveforms.
• Employed model-based reconstructions using regularized nonlinear inversion for joint estimation of anatomical images, coil sensitivities, and velocity maps.

Main Results:

• Achieved real-time 2D and 3D phase-contrast MRI of the human aortic arch at 3 Tesla.
• Demonstrated resolutions of 53 ms (2D) and 67 ms (3D) without ECG synchronization or free breathing.
• Validated the technique using pulsatile flow phantoms and in vivo human aorta studies.

Conclusions:

• Real-time multi-directional flow MRI provides novel opportunities for studying complex human blood flow.
• This method avoids risks associated with combining velocity information from multiple heartbeats.
• Further reductions in acquisition time and accelerated computing are needed for broader clinical trials.