The EASI project uses health telematics to increase the resources available to the inter-disciplinary tasks of Image-Guided Therapy. Advanced methods for multi-modality image segmentation, registration and visualization for pre-operative surgical planning and intra-operative surgical support are developed. By combining pre-operative image data and intra-operative localization, the project helps to improve effectiveness and quality of clinical interventions while reducing patient risks and overall cost of treatment. This is applied for two clinical application areas: neurosurgery and vascular surgery. The EASI-demonstrators help surgeons to locate anatomical structures on the basis of patient images acquired before and/or during surgery. This guidance facilitates minimally-invasive surgery, and potentially improves accuracy and speed, and reduces risks. Guidance occurs through an optical localizer which measures the position of surgical tools. Once the patient and the pre-operative images have been correlated, the surgical tools can be overlaid on patient images in real-time, showing the surgeon the position and orientation of the tools in relation to the patient's anatomy and pathology. Demonstrator software has been promoted into product software. The demonstrator's software implementation has been taken as a starting point for actual production by EasyGuide(tm)/EasyVision engineering groups. The cooperation of the technical parties involved consolidating their results in the common software platform resembling the product. By implementing the demonstrator and successively refining it in the course of the verification and validation phases, a better understanding has been reached of the technical feasibility of what is clinically required, and of the problems which remain to be solved on the road to production, and in future versions of the product, as well as an estimate of the capacities/cost associated with further production. By exposing the demonstrators to a large clinical audience, a better understanding of the commercial possibilities has been gained.