Characterization of highly pixelated CZT detectors for sub-millimeter PET imaging

Cadmium Zinc Telluride (CZT) detectors with 600¿m pitches and 350¿m pitches in 5mm thickness were developed and tested for investigation pixilated CZT detector applications in Positron Emission Tomography. In addition to flood ¿-ray source measurements (662keV, 122keV and 59.5keV), we scan across pixels with a collimated Co-57 source (collimated beam size < pixel size) with a step size 50¿m. We sorted events based on the number of pixels that detect a charge signal (single, double, triple) and analyzed the charge sharing at different energies for detectors of different pitches. Results show the number of charge sharing events increases when ¿-ray energy increases or when pixel size decreases. Based on the collimated beam measurements of energy at 122keV, the charge sharing range in a 5mm thick CZT detector biased at -1000V was estimated to be around 125¿m FWHM for both 600¿m and 350¿m pitched anodes, while the charge loss is more severe in 350¿m pitched detectors than in 600¿m pitched detectors.