In clinical practice, there is a growing tendency to use multiple imaging modalities for a detailed examination of the same anatomical structure over again, in order to acquire as much information as possible to make a correct diagnosis. At the NTUA, the National Technical University of Athens, a pilot system has been developed to combine images of human electric potentials inside the patient's body with computed tomography (CT) data from the same person as to prepare the information for visualization and manipulation via the World Wide Web (WWW). The researchers hope to contribute to an improved method for diagnosis by taking a first but decisive step towards virtual reality as a useful technique in current Medical Imaging Systems.
Four researchers from the Institute of Communications and Computer Systems (ICCS) at NTUA, have designed a hardware and software platform to measure electric potentials (EP) on the skin through a range of external electrodes, placed round the thorax at the level of the heart. The value of the electric potential inside the patient's body is reconstructed by means of an algorithm to produce a 3D image. The advanced software generates this EP image of which the voxels are labelled with the help of a conventional CT image. The CT image is segmented and registered together with the EP image for triangulation to obtain a Virtual Reality Modelling Language or VRML file.
For this purpose, the scientists apply a marching cubes (MC) algorithm to create the VRML output for accurate visualization via the World Wide Web (WWW). In the next step, the information of the EP image is fused on the VRML as colour data for a detailed vision of the electric potentials on the enclosing surface of the anatomic structure. This data can be rendered in real time on high end PCs, using a simple Web browser. The ICCS research team seems to have succeeded in combining the traditional optimal signal processing programmes with user-friendly, platform independent JAVA tools for image generation to offer a qualitative 3D representation of patient data for diagnostic analysis in cardiology.
The scientists have selected EP as the principal viewing modality because the heart constantly generates electrical current sources. The surface potentials obtained from the thoracic zone via the electrode belt, display the electrical activity of the heart in a 3D representation, which has been enhanced with the CT data to identify the tissues of interest, such as blood, bone, cardiac muscle, lungs, fat, and skin. As a result, the innovative imaging method will be of great clinical value in a broad range of cardiac diseases relating to ischemia and arrhythmogenic disorders. You can find a full description of the pilot system in Volume 14, June 1998, Numbers 1-2, pp. 67-77 of Future Generation Computer Systems. For more information, you can contact Dr. Christian Michael at NTUA.