A Novel Algorithm to Create Quantitative X-Ray Images Based on Precise Analysis of Polychromatic X-Ray Attenuation

Photon counting is a technique which has the potential to make a breakthrough in X-ray image diagnosis by taking advantage of the ability to utilize X-ray energy information. Focusing attention on the CdZnTe-type energy-resolving photon-counting detector (ERPCD), we aim to realize highly accurate material identification based on analysis of polychromatic X-rays. When analyzing X-rays accurately, we should understand that the X-ray energy information is distorted by the beam hardening effect (depending on the object) and the response function of the detector. In our method, these effects are corrected pixel by pixel, which allows for ideal analysis when treating polychromatic X-rays as if they were monochromatic X-rays. As examples of this analysis, we introduce algorithms for deriving effective atomic numbers and separating components of the soft tissue and bone. To demonstrate the practicality of our method, we performed statistical analysis based on a simulation study and clarified the possibilities of clinical applications using actual images of biological samples measured with a prototype ERPCD. Our analysis is based on knowledge of radiation physics that is common to all studies dealing with ERPCDs. We hope that these results will lead to innovations in medical and industrial technology.