Imaging Technology: The Emerging Revolution in Toxicology and Risk Assessment
David S. Lester, Food and Drug Administration, Center for Drug Evaluation and Research, Division of Applied Pharmacology Research, Laurel, MD 20708
Imaging technologies, including CT scanning, Magnetic Resonance Imaging (MRI), and ultrasound, have had a tremendous impact on the clinical sciences, in particular, the diagnosis of disease. These techniques allow rapid, noninvasive, high-resolution analysis of the state of disease progression of many pathologies. In addition, imaging can be used to monitor the progress of treatments. Examples will be given. Imaging approaches can be used to monitor structural and/or functional changes of numerous tissues. Structures or activities can be monitored using intrinsic or extrinsic markers or probes. In general, MRI is most useful for detecting and locating structural changes, which may be a strong indicator of potential toxicity. Functional changes are more complex to interpret as it is difficult to distinguish between the pharmacology vs. the toxicology. While the majority of imaging technologies have been designed for clinical procedures, there is increasing interest in the application of these approaches to animal models. This provides an opportunity to monitor the same animal over an extended treatment period. It may supply some insight into biological endpoints that could be monitored in the clinical trials. The use of imaging for identification of potential surrogate markers will be discussed. It is clear that imaging has not been directed towards toxicology and risk assessment, however, the potential is there and should be encouraged by industry, academics, and government regulatory agencies.