Molecular Imaging of Pulmonary Disease In Vivo

Abstract

Characterization and noninvasive measurement of molecular pathways and biochemistry in living cells, animal models, and humans at the cellular and molecular level is now possible using remote imaging detectors. Positron and single photon emission tomography scanners, highly sensitive cameras for bioluminescence and fluorescence imaging, as well as high-magnetic-field magnetic resonance imaging scanners, can be used to study such diverse processes as signal transduction, receptor density and function, host response to pathogens, cell trafficking, and gene transfer. In many cases, images from more than one modality can be fused, allowing structure-function and multifunction relationships to be studied on a tissue-restricted or regional basis. ''Molecular imaging'' holds enormous potential for elucidating the molecular mechanisms of pulmonary disease and therapeutic response in intact animal models and humans.Keywords: molecular imaging; positron emission tomography; optical imaging; magnetic resonance imaging; imaging reporter genes Molecular imaging is broadly defined as the characterization and measurement of biological processes in living animals, model systems, and humans at the cellular and molecular level using remote imaging detectors. With refined genomic maps of human, mouse, and many pathogens completed, genetic information is expected to lead to new medical therapies, diagnostics, and ultimately to cures previously not imagined. In the post-genomic era, wherein functionality will be added to this vast array of genetic information, opportunity exists for imaging to play a significant role in basic and translational research as well as clinical care of patients. Molecular imaging offers an unprecedented opportunity to identify, follow, and quantify biologic processes at the cellular and subcellular level in intact organisms. In the long term, molecular imaging may provide a seamless translation for studies in cells to animals and, ultimately, to humans.The ability to image fundamental biological processes, such as receptor occupancy, cell trafficking, and drug action, provides ample reason to employ molecular imaging strategies in studies of pulmonary disease. Molecular imaging capitalizes on recent advances in the techniques of molecular and cell biology, on new highly specific probes that serve as sources of imaging signal, and on significant improvements in imaging instrumentation specifically designed for small animal imaging. In this brief review, we highlight and illustrate a few of the general types of imaging studies that are being conducted (or could be) to investigate pulmonary disease. In-depth, general reviews of molecular imaging are available elsewhere (1-6). GENERATING SIGNAL IN MOLECULAR IMAGING: APPRAISAL OF VARIOUS STRATEGIESOverall, imaging reagents can comprise injectable and inhalable contrast agents, and radiopharmaceuticals, with or without activation strategies, or genetically encoded reporters. These reagents are all useful in biological studies, but injectable or inhalable agents...

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