Counting-loss correction procedure of X-ray imaging detectors with consideration for the effective atomic number of biological objects

It is necessary to correct counting loss caused by the pulse pile-up effect and dead time when using energy-resolving photon-counting detectors (ERPCDs) under “high-counting-rate” conditions in medical and/or industrial settings. We aimed to develop a novel counting-loss correction procedure in which biological objects having effective atomic numbers (Zeff values) of 6.5–13.0 are measured with polychromatic X-rays. To correct for counting loss, such a procedure must theoretically estimate the count value of an ideal X-ray spectrum without counting loss. In this study, we estimated the ideal X-ray spectrum by focusing on the following two points: (1) the X-ray attenuation in an object (Zeff values of 6.5–13.0) and (2) the detector response. Virtual materials having intermediate atomic numbers between 6.5 and 13.0 were generated by using a mixture of polymethylmethacrylate (PMMA, Zeff = 6.5) and aluminum (Al, Zeff = 13.0). We then constructed an algorithm that can perform the counting-loss correction based on the object’s true Zeff value. To demonstrate the applicability of our procedure, we analyzed investigational objects consisting of PMMA and Al using a prototype ERPCD system. A fresh fish sample was also analyzed. The Zeff values agree with the theoretical values within an accuracy of Zeff ±1. In conclusion, we have developed a highly accurate procedure for correcting counting losses for the quantitative X-ray imaging of biological objects.