Rapid quantification of regurgitant flow through mitral valve models using the control volume method with segmented k-space magnetic resonance velocimetry

Abstract

New approaches for the assessment of mitral regurgitation have focused on the quantification of the regurgitant flow volume, but they are accompanied by uncertainties. Recently, a control volume (CV) method applied via multi-slice and 3-directional magnetic resonance phase velocity mapping (MRPVM) showed potential for accurate quantification of the regurgitant volume. A limitation of conventional non-segmented MRPVM is its relatively long scan time. With the development of new rapid segmented k-space sequences, fast velocity measurements have become possible. The aim of this study was to evaluate in vitro the accuracy of segmented k-space MRPVM in quantifying the regurgitant volume using the CV method. Four mitral regurgitant orifices were tested under a variety of flow conditions. Five contiguous slices were placed in the sagittal direction and all three velocity components were measured with a segmented MRPVM sequence with nine lines per segment. Non-segmented MRPVM measurements were also performed to provide reference data. Rotameter readings provided true flow rates. Comparison between the segmented MRPVM results and the true flow rates showed close agreement when a medium-sized CV was used (> 0.5 cm in all directions). With a very small CV, significant errors were introduced because of aliasing and rapid acceleration very close to the orifice.