This chapter will introduce the issues of major importance in medical imaging. These elements will be examined first through the technological evolution and the clinical areas of concern. After a brief overview of medical imaging issues, the third section is devoted to image analysis going from reconstruction, segmentation, and object extraction up to object modeling (shape description and metrics derivation). These key steps, extensively developed in the other chapters of the book, raise a number of questions about our capability to detect, precisely delineate the organs and characterize the lesions from one imaging modality or multiple sources (i.e. multimodal imaging where image fusion and the accompanying registration problems have to be solved). The next section brings more insights into three topics not covered in the sequel of the book : (i) motion analysis in 2-D or 3-D image sequences; (ii) virtual reality which allows medical operations to be simulated, planned and controled, and (iii) the evolution from intermediate to high level description, a necessary step between low level and interpretation level. They suppose high technology environments and also efficient solutions to realistically view, track and act on the organs.