In vivo imaging of gene and cell therapies

Molecular imaging can be broadly defined as the in vivo characterization an d measurement of biological processes at the cellular and molecular level. In contrast to commonly used clinical imaging, it sets forth to probe the m olecular abnormalities that are the basis of disease, rather than imaging t he end effects of these molecular alterations. Development of new imaging t echnologies requires a multidisciplinary collaboration between biologists, chemists, physicists, and imaging scientists to create novel agents, signal amplification strategies, and imaging techniques that successfully address these questions. In this article we attempt to present some of the recent developments and show how molecular imaging can be used, at least experimen tally, to assess specific molecular targets for gene- and cell-based therap ies. In particular, we place emphasis on the development and use of experim ental small-animal models, which are particularly inclined toward this appr oach, primarily in combination with magnetic resonance (MR), radionuclide, and optical imaging. In the future, specific imaging of disease targets wil l allow earlier detection and characterization of disease, as well as earli er and direct molecular assessment of treatment efficacy. (C) 2001 Internat ional Society for Experimental Hematology. Published by Elsevier Science In c.