Opacity modulation for interactive volume rendering of medical images

Interactivity is a main requirement for 3D visualisation of medical images in a variety of clinical applications. The good matching between segmentation and rendering techniques is essential to design easy to use interactive systems which assist the physicians in dynamically creating and manipulating "diagnostically relevant" images from the volumetric data sets. In this work we consider the above problem within an original interactive visualisation paradigm. By this paradigm we want to highlight the twofold clinical requirement of a) detecting and visualising the structures of diagnostic interest (SoDI's) and b) adding to the 3D scene some other structures to create a meaningful visual context. Being the opacity modulation of the different structures a crucial point, we propose an opacity management which reflects the paradigm ideas and operates by means of a twofold indexed look-up table (2iLUT). the 2iLUT consists of a combination of attribute based and object based opacity management and is here designed and experimented in order to combine the time interaction benefits of an indexed opacity setting with the effective handling of the above classification and visualisation clinical requirements.