Simulation of Brisk and Fast Phase-Contrast Magnetic Resonance Imaging by Computational Fluid Dynamics

Cardiac synchronized magnetic resonance imaging of flowfields has suffered due to the relatively long acquisition times required. We developed a rapid MRI approach, BRISK PCA (Block Regional Interpolation Scheme for k-space Phase Contrast Angiography) which was simulated here using data generated by computational fluid dynamics to investigate the role of interpolation and segmentation on the accuracy and efficiency of the method. BRISK differs from other sparse sampling schemes in that the sampling rate is a function of the position in k-space and interpolation is used to generate data points not directly acquired. Combined with conventional segementation, this allows more efficient use of time, resulting in rapid acquisitions with good spatial and temporal resolution. FAST (Fourier AcquiSition in Time) is a similar sparse sampling strategy that varies the segmentation factor, rather than the sampling rate, as a function of k-space position. BRISK and FAST can be performed in nearly equally scan times. However, deviation from ideal in the FAST data was highly dependant on the starting phase of the flow waveform, while BRISK was immune to such variation. Simulations showed that BRISK (up to segmentation factor 5) and FAST 5 retained excellent axial-velocity accuracy, but the accuracy of FAST was variable and dependent on waveform characteristics.