Motion-resolved real-time 4D flow MRI with low-rank and subspace modeling

Area of Science:

• Medical Imaging
• Cardiovascular MRI
• Blood Flow Dynamics

Background:

• Conventional 4D flow MRI often requires electrocardiogram (ECG) synchronization and respiration control, limiting real-time motion-resolved imaging.
• Quantifying and visualizing blood flow velocities with high spatiotemporal resolution remains a challenge in cardiovascular magnetic resonance imaging (MRI).

Purpose of the Study:

• To develop a novel motion-resolved, real-time four-dimensional (4D) flow MRI technique.
• To enable quantification and visualization of three-directional blood flow velocities without ECG gating or respiration control.

Main Methods:

• An integrated real-time 4D flow MRI method combining specialized k-space acquisition, low-rank subspace reconstruction, and data-binning postprocessing.
• Utilized interleaved acquisition of training and imaging data to exploit spatiotemporal correlations for reconstructing time-series images from undersampled k-space data.
• Constructed a five-dimensional dataset (x-y-z-cardiac-respiratory) for analyzing respiration-dependent flow variations.

Main Results:

• Achieved 2.4 mm isotropic spatial resolution and 34.4 ms temporal resolution for aortic blood flow measurement.
• Demonstrated good agreement with conventional 4D flow MRI in healthy subjects.
• Successfully resolved beat-by-beat pathological flow variations in patients with atrial fibrillation, outperforming conventional methods.

Conclusions:

• The developed real-time 4D flow MRI method enables high-resolution, motion-resolved imaging without ECG gating or respiration control.
• The technique accurately captures beat-by-beat blood flow dynamics and respiration-dependent flow information.
• This advancement offers improved capabilities for cardiovascular flow analysis, particularly in complex hemodynamic conditions.