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Small Animal Imaging: Project Synopsis

The Project to Achieve High Resolution Three Dimensional Imaging of Gene Expression in Live Animals

The Jefferson Lab's Detector and Imaging Group is collaborating with the Department of Biology at the College of William and Mary (Dr. Margaret Saha, PI), and the UCLA Crump Institute of Biological Imaging (Dr. Simon Cherry, co-PI) to develop a high resolution gamma imager for small animals. A prototype detector has been tested at the Department of Biology of the College of William and Mary and is being optimized for detection of the gamma radiation of Iodine-125. The detector system is composed of a single imaging detector head composed of a 5 inch diameter position sensitive photomultiplier tube coupled to a scintillator crystal array. The system presently can achieve 1.5 mm resolution (FWHM).

Iodine-125 is the isotope that is used with certain molecular biology techniques to probe for certain gene products in a live animal. The ability to image gene expression in vivo in live animals will provide a valuable tool for molecular biology and human disease research. Current gene expression techniques take in vitro snapshot of the state of expression of the gene of interest. In order to get a an actual measurement of the animal9s state of expression of the gene of interest for instance in a brain, the animal's life must be terminated. The National Science Foundation has awarded funds for this project to advance studies involving neurobiology. Other examples of applications of small animal gamma imagers include studies of human cancers, such as cancers of prostate and breast, in animal models.

The next phase of this project is to implement rapid computer tomography by applying the single photon emission computer tomography (SPECT) technique. The present system has a single imaging detector head that requires long scanning times which are not realistic for most animal studies. Several more imaging detector heads would need to be incorporated onto a scanning gantry to allow for adequate statistics in a realistic time frame. In addition, it is possible to achieve sub-millimeter spatial resolution by utilizing recently developed compact position sensitive photomultiplier tubes. This enhancement would be of great benefit to the present small animal imaging application.

The Detector and Imaging Group also recently installed a small version of the I-125 imager in the Weizmann Institute, Rehovot, Israel (Dr. Amos Breskin, PI) and an imager to image Tc-99m uptake at the University of Athens, Greece (Dr. Nikos Giokaris, PI). In both cases the imagers will be used in cancer research using mice.