Coregistration and visualization of cardiac CT studies and dynamic PET studies using scene-graphs, direct volume rendering and 2D transfer functions

717 Learning Objectives: After reviewing this presentation, attendees will be able to: 1. Understand how CT data can be classified and visualized with transfer functions. 2. Describe how functional PET data and anatomic CT data can be displayed in the same 3D scene. Abstract (summary): Recent advances in CT technology offer a non-invasive way for revealing the degree and location of stenosis of the coronary arteries. PET can be used to quantify physiologic processes, including myocardial perfusion. The combination of anatomic and physiologic information offers new possibilities in diagnosis of coronary artery disease, no matter if the data comes from stand-alone devices or from PET/CT. The software currently supplied by the vendors of imaging devices has two major limitations. In CT, tools for visualization of the coronary arteries exist, but segmented data usually cannot be exported in a format that allows further processing. In PET, only static data can be used for coregistration, sacrificing valuable diagnostic information. In our software, we use two dimensional transfer functions to highlight clinical relevant details from the CT study, i.e. the coronary arteries, without the interference of other anatomical structures. Attenuation coefficient and gradient magnitude are displayed in a 2D histogram on which different filters can be defined. Direct volume rendering is used to show the effect of the filters in real-time. PET and CT currently are co-registered manually. A PET uptake image (e.g. the last frame of a dynamic study using N-13-ammonia) is used for coregistration. A converter written in MATLAB transforms the functional data derived from compartment modeling back into anatomical space, where it can be added to the scene-graph. Our software runs on commercial personal computers with powerful graphics cards (GPU) and thus is independent from specific vendors of clinical imaging devices. This also offers the possibility to introduce the software into the clinician’s office.