ABSTRACT
Technological innovations over the past several decades have led to pixelated photon-counting x-ray detectors suitable for medical imaging applications. One component of this research effort is the development of mathematical models of detector performance. Such models provide physical insight and understanding of relationships between the basic physics of photon-counting x-ray detectors and image quality. Models also enable identifying upper limits of detector performance, establishing performance benchmarks, and optimizing detector design. Over the past several decades, the image science community developed a Fourier-based approach to the objective assessment of detector performance. Within this framework, image spatial resolution and image noise are quantified in terms of the modulation transfer function and noise power spectrum, respectively. These metrics are combined in the detective quantum efficiency, which provides an objective measure of the signal-to-noise performance of an x-ray imaging system as a function of spatial frequency. In this chapter, we summarize recent efforts to develop a framework for modelling and understanding of Fourier-based metrics of the performance of photon-counting x-ray detectors. We present a brief introduction to Fourier-based metrics of image quality, present a generic framework for modelling of Fourier-based metrics for photon-counting systems, and then present a simple model of a photon-counting detector that enables understanding relationships between detector design parameters, spatial resolution, and image noise. The development of models of the performance of photon-counting x-ray imaging systems is an ongoing effort and future research is expected to transcend the material presented in this chapter.
