Accuracy of linear attenuation coefficients measured with a photon counting CT system

The purpose of our research is to develop a photon counting CT system with a semiconductor detector. The photon counting CT system enables us to decompose materials, and this information is useful to diagnose diseases. We developed a new CdTe detector that was able to measure x-rays with the count rate of 10⁷ counts/sec/mm² with four energy windows. The size of a CdTe detector module was 8×8 mm², and that of a pixel was 0.2 × 0.2 mm². The thickness of the detector was 1 mm. The active area of our detector was 8 × 144 mm². We evaluated the performance of the photon counting CT images in terms of the accuracy of reconstructed linear attenuation coefficients. In addition, we compared these reconstructed images with those acquired with the energy integration detector with the CdTe semiconductor detector. The results showed that our detector could reconstruct linear attenuation coefficients with the error ratio of less than 3 % compared with the theoretical value.