In-vitro validation of 4D flow MRI measurements with an experimental pulsatile flow model

Abstract

Purpose: The purpose of this study was to assess the precision of four-dimensional (4D) phase-contrast magnetic resonance imaging (PCMRI) to measure mean flow and peak velocity (V_max) in a pulsatile flow phantom and to test its sensitivity to spatial resolution and Venc.

Material and methods: The pulsatile flow phantom consisted of a straight tube connected to the systemic circulation of an experimental mock circulatory system. Four-dimensional-PCMR images were acquired using different spatial resolutions (minimum pixel size: 1.5×1.5×1.5mm³) and velocity encoding sensitivities (up to three times V_max). Mean flow and V_max calculated from 4D-PCMRI were compared respectively to the reference phantom flow parameters and to V_max obtained from two-dimensional (2D)-PCMRI.

Results: 4D-PCI measured mean flow with a precision of -0.04% to+5.46%, but slightly underestimated V_max when compared to 2D-PCMRI (differences ranging from -1.71% to -3.85%). 4D PCMRI mean flow measurement was influenced by spatial resolution (P<0.001) with better results obtained with smaller voxel size. There was no effect of Venc on mean flow measurement. Regarding V_max, neither spatial resolution nor Venc did influence the precision of the measurement.

Conclusion: Using an experimental pulsatile flow model 4D-PCMRI is accurate to measure mean flow and V_max with better results obtained with higher spatial resolution. We also show that Venc up to 3 times higher than V_max may be used with no effect on these measurements.

Keywords: 4D flow magnetic resonance imaging (MRI); Experimental studies; Phase-contrast magnetic resonance imaging; Pulsatile flow model.