Fast Photon-Counting CZT Detector for CT Imaging

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DESCRIPTION (provided by applicant): The goal of the project is to develop the next generation x-ray computed tomography (CT) detector modules for CT scanners based on high-throughput photon-counting cadmium zinc telluride (CZT) or cadmium telluride (CdTe) detectors combined with CMOS readout arrays. This new technology will deliver significant improvements in diagnostic capabilities compared with the technology currently used by all major CT manufacturers. The currently commercially-available CT systems typically use a detector having silicon (p-n junction) photodiodes that are optically coupled to a scintillator which is operated in a current-integrating mode where the signals generated from the x-rays are integrated in each pixel over a time before the integrated charge is read out. The use of these current-mode detectors results in generally poorer image quality than could be achieved by using the technology proposed in the product presented here. Instead of integrating the x-ray current over an exposure time, high-throughput photon counting is used to measure and count each x-ray individually over a similar period. High throughput is necessary as a very large x-ray flux is utilized in many CT applications. For example, CT scanners can produce ~100 Mphotons/mm2/s in the unattenuated beam. The large flux is required to collect sufficient photon statistics in the measurement of the transmitted flux (the attenuated beam) during the very short time frame of a CT scan. This high count rate combined with a need for high detection efficiency required the development in the Phase I of detector structures that provide a response signal much faster than the transit time of carriers over the whole detector thickness. We will continue the development of detector modules with the necessary capabilities to replace existing CT detector technology and provide new features: counting (and analysis) of each individual x-ray, binning events according to x-ray energies, and spectroscopic x-ray imaging capabilities. These new features lead to: significantly reduced x-ray dose to the patient, compositional analysis of tissue through spectroscopic x-ray imaging, and potentially significant improvement in overall image quality. PUBLIC HEALTH RELEVANCE: Until now, all commercial x-ray computed tomography (CT) systems have utilized integrating detectors. By combining high-throughput photon-counting cadmium zinc telluride or cadmium telluride detectors with CMOS readout arrays, we will achieve a significant breakthrough in x-ray CT performance. These new features lead to potentially significantly reduced x-ray dose to the patient, compositional analysis of tissue through spectroscopic x-ray imaging, and potentially significant improvement in overall image quality.