Development of a novel radiation imaging detector system for in vivo gene imaging in small animal studies

We report preliminary results from a prototype of radiation imaging technology which takes advantage of the emission properties of the radioisotope iodine /sup 125/I as the probe. The detector system utilizes crystal scintillators and a position sensitive photomultiplier tube. Iodine 125 decays via electron capture emitting a 35-keV gamma ray with the prompt emission of several 27-32-keV K/spl alpha/ and K/spl beta/ shell X-rays. Because of this, a coincidence condition can be set to detect the /sup 125/I decay, thus reducing background radiation contribution to the image. The prototype detector we report has a limited sensitivity and detection area because of the size of the scintillators and photomultiplier tubes, yet it performed well enough to demonstrate the viability of this method for imaging /sup 125/I in a mouse. Mouse imaging studies of iodine uptake by the thyroid and melatonin binding have been done with this detector system using doses of /sup 125/I alone or attached to the melatonin. Many studies in molecular biology follow the expression and regulation of a gene at different stages of an organism's development or under different physiological conditions. Molecular biology research could benefit from this detection system by utilizing /sup 125/I-labeled gene probes.