Response Function Estimation for the Photon Counting Detector using Multiple Balanced KEdge Filters

Abstract

Photon counting detectors (PCDs) have the capability of discriminating the incident photons of different energy and the technique becomes more and more mature in nowadays. However, the energy response functions of PCDs are not ideal and may cause spectral distortion. The goal of this work is to estimate the energy response functions using conventional X-ray source and filters. Recently, spectral CT using multiple balanced K-edge filters is proposed and this provides a new method to calibrate the equivalent spectrum. In this work, we analyze the transmission matrix with different filters by singular value decomposition (SVD). To get a stable solution, the rank of the transmission matrix should be larger than the rank of the response matrix, which equals to the total number of energy channels. The simulation results show that the rank of transmission matrix with multiple balanced K-edge filters is larger than the rank of transmission matrix with step-wedge filters. The equivalent spectrum calculated with K-edge filters is accurate. The experiment results validate the conclusion. Using multiple balanced k-edge filters, we can estimate the equivalent spectrum of photon counting detectors easily and flexibly in more detected energy channels.