Velocity vector reconstruction for real-time phase-contrast MRI with radial Maxwell correction

Area of Science:

• Medical Imaging
• Magnetic Resonance Imaging
• Biomedical Engineering

Background:

• Phase-contrast MRI (PC-MRI) is crucial for non-invasive blood flow quantification.
• Accelerated imaging techniques are needed to achieve real-time data acquisition.
• Existing methods struggle with reconstruction instabilities and phase errors from magnetic field variations.

Purpose of the Study:

• To develop an auto-calibrated, model-based image reconstruction for highly accelerated multi-directional PC-MRI.
• To compensate for phase differences near $$ and phase errors caused by concomitant magnetic fields.
• To enable real-time velocity vector mapping with improved accuracy.

Main Methods:

• Extended nonlinear inversion reconstruction to multi-directional flow using multiple flow-encodings.
• Introduced a smoothing constraint to penalize phase wraps and resolve solution space ambiguity.
• Incorporated Maxwell terms on a line-by-line basis to correct for concomitant magnetic field-induced phase errors.

Main Results:

• Achieved real-time three-directional velocity mapping in the aortic arch at 1.8 × 1.8 × 6 mm³ spatial and 60 ms temporal resolution.
• Successfully avoided artificial phase wraps using the smoothness constraint.
• Demonstrated effective compensation for inter-spoke magnetic field differences via integrated radial Maxwell correction.

Conclusions:

• Nonlinear inversion-based velocity vector reconstructions enable significant radial data undersampling for real-time multi-directional PC-MRI.
• The choice between spoke-wise or frame-wise Maxwell term correction depends on specific application requirements.
• This advancement facilitates faster and more accurate cardiovascular and neurovascular flow imaging.