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

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

Maria Aristova, Jianing Pang, Yue Ma, Liliana Ma, Haben Berhane, Vitaliy Rayz, Michael Markl, Susanne Schnell

Abstract

Purpose

Dual-velocity encoded (dual-venc or DV) 4D flow MRI achieves wide velocity dynamic range and velocity-to-noise ratio (VNR), enabling accurate neurovascular flow characterization. To reduce scan time, we present interleaved dual-venc 4D Flow with independently prescribed, prospectively undersampled spatial resolution of the high-venc (HV) acquisition: Variable Spatial Resolution Dual Venc (VSRDV).

Methods

A prototype VSRDV sequence was developed based on a Cartesian acquisition with eight-point phase encoding, combining PEAK-GRAPPA acceleration with zero-filling in phase and partition directions for HV. The VSRDV approach was optimized by varying z, the zero-filling fraction of HV relative to low-venc, between 0%–80% in vitro (realistic neurovascular model with pulsatile flow) and in vivo (n = 10 volunteers). Antialiasing precision, mean and peak velocity quantification accuracy, and test–retest reproducibility were assessed relative to reference images with equal-resolution HV and low venc (z = 0%).

Results

In vitro results for all z demonstrated an antialiasing true positive rate at least 95% for $$ {R}{\mathrm{PEAK}-\mathrm{GRAPPA}} $$ = 2 and 5, with no linear relationship to z (p = 0.62 and 0.13, respectively). Bland–Altman analysis for z = 20%, 40%, 60%, or 80% versus z = 0% in vitro and in vivo demonstrated no bias >1% of venc in mean or peak velocity values at any $$ {R}{\mathrm{ZF}} $$. In vitro mean and peak velocity, and in vivo peak velocity, had limits of agreement within 15%.

Conclusion

VSRDV allows up to 34.8% scan time reduction compared to PEAK-GRAPPA accelerated DV 4D Flow MRI, enabling large spatial coverage and dynamic range while maintaining VNR and velocity measurement accuracy.