Radionuclide imaging is an important tool for observing physiological processes within the brain and other organs. Traditional radionuclide imaging systems rely on scintillator-based detectors. Wide bandgap semiconductors such as cadmium zinc telluride (CZT) offer significant advantages over scintillator-based systems including superior energy and spatial resolution, compactness, and better signal to noise ratio. To date, most detector grade CZT is grown by the High Pressure Bridgman (HPB) technique in U.S.A. Detector grade material is costly because of low yields. Imarad (Israel) is making large-size CZT using low presure horizontal Bridgman technique with lower price, but the CZT with very low resistivity will increase the detector noice. The goal of the Phase II project is to optimize an alternative crystal growth method, the modified vertical Bridgman (MVB) technique, for growing larger size and lower cost CZT for nuclear imaging in united states. Thus, the specific aims of the Phase II research are: 1. Continue to optimize the growth of 3"""""""" diameter CZT ingots using MVB technique. 2. Construct a 4"""""""" diameter MVB furnace and use it to produce lager-size CZT wafers for imaging applications 3. Systematically characterize all MVB grown 3"""""""" and 4"""""""" diameter ingots to evaluate yields and provide feedback for Aim 1 and 2. 4. Develop the capability to prodcess CZT detectors including those with complex electrode geometries such as pixel arrays. This research will produce an important nuclear medicine imaging tool for bedside and will also monstrate the full potential of the new MVB CZT technique in nuclear medicine.