Abstract #3961

RF Pulse Designs for Velocity-Selective MRA at Low Field Strengths

Ziwei Zhao¹, Nam G. Lee², and Krishna S. Nayak^1,2

¹Ming Hsieh Department of Electrical and Computer Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA, United States, ²Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA, United States

Velocity‐selective (VS) RF pulses can differentiate flowing blood from background tissue, and have been utilized for non-contrast intracranial, abdominal, and peripheral angiography at 3T. Here, we explore RF pulse designs for intracranial VS-MRA at low field strengths including 0.55T. We evaluate pulse performance using simulations that incorporate realistic levels of B₀ variation, B₁⁺ variation, and gradient distortions. Compared to 3T, simulations indicate 22% - 38% sharper velocity transitions and/or 50% - 60% less signal loss at 0.55T. We also show that gradient distortions can lead to “stripe” artifacts and can be mitigated with pre-emphasis.

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