New developments in the field of high resolution imaging focus on functional parameters pertaining to disease-specific medical imaging. Such new diagnostic strategies are possible using scintigraphic techniques and, more recently, by MRI and US. In addition, new therapeutic concepts, including gene therapy, require specific tracers or contrast media for therapy monitoring, for example, enzyme activity and changes in receptor expression. For this purpose scientists conducting basic research, expecially molecular biologists, and clinicians must collaborate in order to exploit the available interdisciplinary knowledge in the development of new imaging technologies so as to incorporate the molecular signals of diseases.