Spectrum-Based Calibration Method for Energy Discriminating CZT Detectors Using Commercial X-Ray Generators

Cadmium zinc telluride array detectors are known to have large pixel-to-pixel heterogeneity, which is undesirable in spectral computed tomography, and is hard to be theoretically modeled. To get better image quality and reduce the ring artifact, spectral calibration has to be done for each pixel to get uniform energy responses. Traditionally, multiple radionuclides with known characteristic emission peaks are used to calibrate the detectors. Heterogeneity of pixel responses can be compensated by electronically adjusting the gain and offset. This method is straightforward and simple, but radionuclides may not be readily available to many laboratories. In this paper, we present a method to calibrate the spectral response of each pixel with the broad spectrum features of commercial X-ray generators. For our system, the spectral response was empirically assumed to be Gaussian. A simple recursive fitting method was used to identify the intrinsic amplification and offset properties of each pixel. Gain and offset calibration were done accordingly. This method is robust, accurate, and fast, which is potentially applicable to other detectors with adaption.