Structure size enhanced histogram: A transfer function for 3D volume visualization

Direct volume visualization requires the definition of transfer functions (TFs) for the assignment of opacity and color. Multi-dimentional TFs are based on at least two image properties, and are specified by means of 2D histograms. In this work we propose a new type of a 2D histogram which combines grey value with information about the size of the structures. This Structure Size Enhanced (SSE) histogram is an intuitive approach for representing anatomical features. Clinicians - the users we are focusing on - are much more familiar with selecting features by their size than by their gradient magnitude value. As a proof of concept, we employ the SSE histogram for the definition of two-dimentional TFs for the visualization of 3D MRI and CT image data.