Applications of In Vivo Molecular Imaging in Biology and Medicine

After completing this article, readers should be able to: 1. Describe the clinical applications for which molecular imaging may be most effective in the near term and the research applications of molecular imaging that are relevant to clinical imaging. 2. Delineate the significance of data generated by current molecular imaging studies. The methods of in vivo molecular Wimaging have arisen out of the need for in vivo assays in many different fields; it is the progress in each of these fields that has led to a wealth of new tools for in vivo molecular and cellular analyses. In vivo molecular imaging has been used in the study of gene expression and cell migration during mammalian and other vertebrate development, in the evaluation of animal models of human cancer, in drug discovery, and in revealing patterns of infectious disease and host response to infection. In highlighting some of these studies, we illustrate the overall goals of in vivo analysis and some of the challenges for future studies. A spectrum of optically based imaging strategies, and more recently, nuclear magnetic resonance imaging approaches have revealed cellular and molecular changes that occur during development in mouse, fish, chick, and frog embryos.1,2 The goal of in vivo imaging in the study of development is to evaluate the molecular events that occur as an embryo executes cell migration or as a specific cell divides and gives rise to daughter cells that have distinct and mature phenotypes. The challenge lies in performing assays at the cellular and molecular levels within the intact embryo while maintaining as normal a setting as possible. The imaging strategies used to study embryonic development, typically light microscopy, generally can address questions at the cellular level, but the future of developmental biology lies in linking these analyses, which reveal how and …