Visualization of Cardiac Blood Flow Using Anisotropic Ambient Occlusion for Lines

Abstract

Ambient occlusion (AO) for lines (LineAO) was introduced by Eichelbaum et al. [EHS13] as an adaption of screen-space AO to static line bundles, such as white brain matter fiber tracts derived from diffusion tensor imaging (DTI). In this paper, we further adapt the LineAO technique to dynamic scenes, in particular the animation of blood flow-representing pathlines that were integrated in cardiac 4D phase-contrast magnetic resonance imaging (PC-MRI) data. 4D PC-MRI is a non-invasive technique that allows to acquire time-resolved blood flow velocity data in all three spatial dimensions, i.e., a 4D vector field of one heart beat. Our main extension is a line alignment factor that reduces the AO-induced darkening if nearby lines have similar screen-space tangents. We further enhance the perception of homogeneous flow by incorporating depth-dependent halos. Our technique facilitates the quicker identification of prominent flow structures while showing the full flow context.