Minimizing Background Phase in PC-MRI with the Gradient Impulse Response Function (GIRF) and Gradient Optimized (GrOpt) Velocity Encoding

Background phase errors in PC-MRI flow measurements are caused by eddy currents and mechanical vibrations that produce unwanted magnetic fields, thereby reducing velocity measurement accuracy. In this work, we demonstrate that a GIRF measurement can be used to predict the PC-MRI background phase, then used to design gradient optimized (GrOpt) velocity encoding waveforms that minimize these errors. The method is tested in static phantoms and in vivo, where 4.8x to 6.4x reductions in background velocity are seen. Phantom results showed a reduction from 0.74±0.22 cm/s to 0.15±0.12 cm/s, and in vivo results showed reductions from 0.93±0.10 cm/s to 0.13±0.08 cm/s.