Spatial Opacity Maps for Direct Volume Rendering of Regions of Interest

Abstract

Despite the mature state of the volume rendering field, its adoption in medical applications is hindered by its complex parametrization and control, and 2D slice based tools are still preferred for clinical workflows. In this paper, we introduce the concept of spatial opacity maps as an interactive tool for exploring volumetric data focusing on the rendering of features of interest. In a region growing fashion, the maps are dynamically created from a user input on the 2D slices, taking into account not only the density values of the structure but also the topology. Using this approach, an inexperienced user is able to generate meaningful 3D renderings with no need to tweak non-intuitive visualization parameters. The spatial opacity maps are independent of the current visualization parameters and they can be easily plugged into the volume rendering integral and combined with other approaches for region of interest (ROI) visualization. We combine our approach with a simple automatic transfer function generation algorithm to improve the visualization of the contextual data.