Accelerated dual-venc 4D flow MRI with variable high-venc spatial resolution for neurovascular applications

Area of Science:

• Medical Imaging
• Cardiovascular Imaging
• Neuroimaging

Background:

• Dual-velocity encoded (dual-venc or DV) 4D Flow MRI offers a wide velocity dynamic range and high velocity-to-noise ratio (VNR) crucial for accurate neurovascular flow assessment.
• Reducing scan time in DV 4D Flow MRI is essential for clinical applicability and patient comfort.

Purpose of the Study:

• To introduce and evaluate Variable Spatial Resolution Dual Venc (VSRDV) 4D Flow MRI, a technique designed to shorten scan times.
• To assess the accuracy, reproducibility, and antialiasing performance of VSRDV compared to conventional DV 4D Flow MRI.

Main Methods:

• A prototype VSRDV sequence was developed using Cartesian acquisition with PEAK-GRAPPA acceleration and prospectively undersampled high-venc (HV) spatial resolution.
• The VSRDV approach involved varying the zero-filling fraction (z) of HV relative to low-venc (0%-80%) and was tested in vitro and in vivo.
• Quantitative assessments included antialiasing precision, mean/peak velocity accuracy, and test-retest reproducibility against reference scans.

Main Results:

• VSRDV achieved an antialiasing true positive rate of at least 95% for tested parameters.
• Bland-Altman analysis showed no significant bias (>1% of venc) in mean or peak velocity quantification in vitro and in vivo for VSRDV compared to standard DV 4D Flow MRI.
• Velocity measurements demonstrated limits of agreement within 15% in vitro and in vivo.

Conclusions:

• VSRDV enables substantial scan time reduction (up to 34.8%) in DV 4D Flow MRI.
• The technique successfully maintains VNR and velocity measurement accuracy, facilitating broader neurovascular flow characterization.
• VSRDV represents a promising advancement for efficient and accurate cardiovascular and neurovascular flow imaging.