Numerical Simulation of In Vitro Pulsatile Flow and Its Study Using FRISK, a Rapid Phase Contrast Technique

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Purpose:To test the potential of a phase contrast magnetic resonance (PC-MR) sparse sampling technique, fragmented regional interpolation segmentation for k-space (FRISK), to capture complex flow features within a breathhold duration by using numerical simulations and experimental approaches.Materials and Methods:Computational fluid dynamics (CFD) data of three models were generated: a two-chamber orifice flow model simulating valvular regurgitation, a femoral artery model, and a U-shaped model simulating the aortic arch. These data were used to simulate conventional and FRISK PC-MR data acquisitions. FRISK parameters can be adapted for different flow fields to capture either high temporal information or complexly varying spatial information with a temporal component or a mixture of both. In vivo PC-MR images on a healthy volunteer were sampled to compare conventional PC-MR with novel FRISK imaging.Results:In our simulations of three representative models, when only the errors from different sampling sequences were considered, FRISK was shown to maintain or even improve data accuracy while cutting the scan time by at least 50% compared to corresponding conventional PC-MR. By adapting the FRISK parameters for flowfields with different features, FRISK was capable of capturing in-plane and through-plane velocity information with excellent detail in approximately 20 heartbeats breathhold duration. The results of the in vivo MR experiment were consistent with the simulation results, showing that breathhold FRISK imaging improved spatial resolution of the data and maintained adequate temporal resolution compared with breathhold conventional imaging.Conclusion:FRISK, a new MRI sampling sequence that sparsely samples data and aligns acquired data during postprocessing, provides a scan time advantage of approximately a factor of 2 compared to conventional scans, and allowed rapid or breathhold scanning while obtaining acceptable accuracy.

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