Flow quantification using low-spatial-resolution and low-velocity-resolution velocity images

In this report, a flow-quantification method using Fourier velocity encoding (FVE) with limited spatial and velocity resolution is presented. The total flow rate in a vessel corresponds to the first moment of the velocity histogram of spins in the vessel, whereas the spin density of flowing spins is the normalization constant. Because the measured histogram using FVE is distorted by RF saturation effects, the RF saturation effects are first estimated and then accurately compensated by acquiring five velocity-encoded images. The spatial resolution in each image can be relatively low because all stationary spins vanish in the resultant flow map. In a phantom study, the errors in measured flow rates were within +/-10% even when the pixel size was greater than the vessel size. This method was also successfully applied to measure flow in the femoral artery. In general, this method constitutes a basis for analyzing multiple velocity-encoded images and is particularly useful for quantifying slow flow or flow in small vessels. Magn Reson Med 42:682-690, 1999.