Effects of contour propagation and background corrections in different MRI flow software packages

Background Velocity-encoded magnetic resonance imaging (VENC-MRI) is a commonly used technique in cardiac examinations. This technique utilizes the phase shift properties of protons moving along a magnetic field gradient. VENC-MRI offers a unique way of measuring the severity of valve regurgitation by directly quantifying the regurgitation flow volume. Purpose To compare flow analysis results of different software programs and to assess the effect of background correction in sample patient cases. Material and Methods A phantom was built out of Polymethyl methacrylate (PMMA) which provides tubes of different diameters. These tubes can be connected to an external water circuit to generate a water flow inside the tubes. Expected absolute flow quantities inside the tubes were determined from preset tube- and flow-parameters. Different flow conditions were measured with a VENC-MRI sequence and the images evaluated using different software packages. In a second step six randomly selected patients showing different degrees of aortic insufficiency were evaluated in clinical terms. Results The contour propagation algorithms used in the software packages performed differently even on static phantom geometry. In terms of clinical evaluation the software packages performed similarly. Enabling background correction or leaving out manual correction of propagated contours changed results for severity of aortic insufficiency. Conclusion Turning on background correction and manual correction of propagated contours in MRI flow volume measurements is strongly recommended.