Vortical flow feature recognition: a topological study of in vivo flow patterns using MR velocity mapping

Purpose: To describe an automatic method for studying vortical flow features using multidirectional magnetic resonance velocity imaging. Methods: The technique relied on the use of linear differential equations to provide local approximation to the acquired MR velocity data and to identify vortical flow patterns that were characterised by their circular or swirling motion. Two directional MR velocity images were acquired on a 0.5 T system with a TE of 14 ms, slice thickness of 10 mm, and field of view of 30-40 cm. Results: The method was validated using numerical simulation, and the potential of this technique for studying blood flow features was demonstrated in the ascending aorta of a healthy volunteer and that of a patient with Marfan's syndrome. The difference in vortex flow dynamics of the left ventricle between a normal subject and a patient with dilated ventricle was also compared. Conclusion: The approach of detecting critical flow features prior to analysing dynamical indices of the fluid is suited to the topological study of complex flow patterns depicted by MR velocity mapping techniques.