Energy weighting with a CdTe spectrometric detector

The technique of energy weighting takes advantage of the energy information of each photon given by spectrometric detectors. It has been shown that energy weighting can lead to improved image quality in terms of contrast-to-noise ratio (CNR) or significant dose reduction. For low energy photons (<; 40 keV), the photoelectric effect is the predominant interaction and E^-3 is a good approximation to the optimal weighting function. In our studies, we investigate energy weighting with a CdTe spectrometric detector (linear array of 16 pixels) and a large energy-spectrum (100 kV). Measurements are done on a iodinated phantom. We evaluate the evolution of the CNR when using the function Ex and varying x from -4 to 3 for different iodine concentrations. The results show that energy weighting leads to a CNR enhancement of at least 1.67 compared to the case of energy-integrating detectors. The optimal functions were found to be E-1 and E0, respectively for high (20 and 10 mg/cm²) and low (2 and 1 mg/cm²) iodine concentrations. Detector response influences on optimal weighting factors, and hence on CNR according to iodine concentration. We also show that the energy bin size has a relatively small impact on the CNR. Energy weighting with spectrometric detectors seems promising and needs further study.