Photon Counting X-ray CT System with a Semiconductor Detector

In a conventional X-ray CT scanner with Gd₂O₂S detectors, the measured data are the whole X-ray energy deposited to each detector bin. The detection of energy is performed in an integration manner, so that the contribution of photons having low energy is smaller than that of those having high energy. But if we use a semiconductor detector such as CdTe with a photon counting mode, we may obtain valuable information for the medium being imaged. For example, if we obtain some information about energy spectra for detected photons, we can enhance the contrast resolution of media having almost the same linear attenuation coefficient as soft tissues by weighing the counted photons having lower energy. To clarify the validity of our proposed method, we used a CdTe semiconductor detector and reconstructed images with projection data measured with different thresholds in counting X-ray photons.