The goal of this project is to develop the technology to improve the imaging capability of gamma cameras for planar, SPECT and PET application. While present gamma cameras are adequate for imaging low diagnostic doses of single-photon tracers, their low count-rate capability due to signal pileup in the NaI(Tl) detector produces image artifacts, count loss, and lower image quality when gamma flux is high. These situations include (a) positron tracer imaging, which requires an 80-90% reduction in injected dose to avoid pileups, (b) high-dose radionuclide therapy for dosimetry, which can not be imaged because of the lack of fast cameras, (c) dynamic first-pass cardiac imaging, (d) the use of very short-lived tracers to reduce radiation dose and increase patient throughput, and (e) the use of larger NaI(Tl) detectors to reduce whole-body scanning time. This project proposes developing a pileup prevention electronic method (PPE) for use on gamma cameras, which may increase the maximum count rates by 25-50 times. The specific aims of this proposal are (I) to optimize the proposed PPE electronics; (II) to build a mobile experimental camera platform. It would facilitate the development of the electronics and allow testing of human applications in the future; (III) to develop two PPE implementations on the experimental camera platform, a single-zone and a multi-zone. The second design splits the camera into 4 zones with 4 PPE circuits to increase the count-rates even more. (IV) to evaluate the imaging performance of the gamma camera as a function of count-rates in phantoms. This project may allow lower cost gamma cameras to image positron tracers without a dedicated $2.5 million PET camera, and with a much improved image quality over the present gamma camera adaptation since a 10x higher dose may be injected. Direct imaging of radionuclide therapy (RNT) would allow more accurate dosimetry calculations and improve the understanding of RNT. It would also allow simultaneous acquisition of transmission and emission data with one camera head and dual isotopes for quantitative SPECT, with less errors in attenuation correction.