| A new detector for imaging 511 keV gammas is designed as an auxiliary unit for Single Photon Computed Tomography (SPECT) systems. Increased interest in higher energy medical imaging creates a demand for a low cost device that can be used with existing SPECT units. Key design features are: a custom high-resolution collimator, a scintillator formed from plastic optical fibers, and a position-sensitive photomultiplier. High-energy resolution (7.5 mm Full Width at Half Max (FWHM) at a source-to-collimator distance (SCD) of 10 cm), improved total efficiency ;Images are formed using Compton electrons, which are limited to one interaction inside the detector as opposed to detection by photoelectric interactions in conventional cameras. Computer simulations with the radiation transport code EGS4 verified the basic imaging concept and were then used to optimize the detector and collimator designs. A working prototype detector was manufactured, tested and characterized. Positron emitting Germanium-68 (Ge-68) was used as a laboratory point source of 511 keV gammas for testing in place of the typical medical positron source Fluorine-18. A larger area detector was then proposed and simulated as a possible application of this technology. |
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