Local Transparency Control of Medical Slice Images and its Application to Slice-Slice and Slice-Volume Fusion

In medical visualization, 2D slice images of human volume data are important as well as 3D volume rendering. The slice images are advantageous in focusing on regions of interest, while the volume rendering enables us to easily observe the whole region. In this paper, we propose a method to (1) create a transparent slice image, where its opacity is controllable by a user-defined transfer function and to (2) fuse a transparent slice image with another slice image or a volume three-dimensionally with correct depth feel. The transparent slice-slice fusion enables a doctor to observe multiple slices simultaneously. The transparent slice-volume fusion enables a doctor to focus on regions of interest on the slice, while observing the whole volume data. Opacities of the constituent slice images and a volume are both flexibly controllable with user-defined transfer functions. Our method is based on the particle-based rendering, which we recently proposed. The rendering is executable with interactive frame rates.