Simulation study on functional images to optimize radiographic condition using energy resolving photon counting detector

Energy Resolving Photon Counting Detectors (ERPCD) are attracting attention as novel detectors having the potential to generate functional images. Since ERPCD can detect individual X-ray photons with energy discrimination, the differences in attenuations due to different X-ray energies can be analyzed. In previous studies, algorithms for determining effective atomic number (Z
eff
), soft-tissue and bone images were developed. A current research topic related to deriving accurate functional images is optimizing imaging conditions. The purpose of this study is to derive the optimal imaging conditions to improve the performance of ERPCD. In this study, we proposed the availability of high tube voltage imaging based on the simulation study. First, we developed an in-house program to process X-ray images using Mathematica programming software. Second, using our program, the optimal imaging conditions were determined. Then, a demonstration of X-ray images using a digital phantom of the lumber spine was performed to mimic clinical conditions. In our program, the following calculations were taken into consideration: (1) attenuation in objects, (2) actual detector response, and (3) statistical fluctuation. The virtual phantoms of aluminum and polymethylmethacrylate (PMMA) had mass thicknesses of 0.1–80 g/cm
²
. The total number of photons was set to correspond to an entrance surface dose of 0.4 mGy, which is the diagnostic reference level (DRL). Under higher tube voltage conditions such as 120 kV, Z
eff
values were derived in a wide range of thicknesses, and good-quality functional images could be obtained. We believe that our Z
eff
algorithm can be applied to diagnostic imaging such as jawbone and lumber spine. It is expected that functional images using ERPCD will add value to medical diagnosis.