Enhancing Visibility of Blood Flow in Volume Rendered Cardiac 4D PC-MRI Data

Abstract

Four-dimensional phase-contrast magnetic resonance imaging (4D PC-MRI) is a method to non-invasively acquire blood flow in the aorta. This flow is commonly visualized as path lines inside of the vessels. Direct volume rendering (DVR) uses a transfer function to directly render the dataset without needing a manual segmentation. Since the transfer function can be manipulated on the fly, DVR allows fast exploration of the dataset. Using a simple intensity-based transfer function, however, either the intravascular blood flow would be hidden behind the vessel’s front side or the entire vessel has to be culled from the visualization. Therefore, we propose an automated mechanism that reveals the vessel anatomy by removing their front sides based on the viewing direction. This creates an effect similar to frontface culling on surface renderings. The visibility of focus objects inside the anatomy is guaranteed while spatial awareness is mostly maintained due to the presence of anatomical structures as context information. While we were able to confirm the effectiveness of our method in an interview with a collaborating radiologist, it still proved to be somewhat limited by the data quality and lack of a manual segmentation.