Extension of x‐ray imaging linear systems analysis to detectors with energy discrimination capability

Abstract

A figure of merit, the broad-spectrum generalized detective quantum efficiency, which describes the performance of digital detectors designed for broad-spectrum x-ray imaging is derived from linear response theory. This measure of the imaging efficacy of an x-ray sensor is obtained when detector contrast modulation in the domain of x-ray energy is introduced in the Fourier-based analysis of digital systems. A method is proposed to scale existing figures of merit according to the energy-dependent response of the detector and the spectral shape of the x-ray beam. The new figure of merit obtained with this method provides an extended description of system performance when comparing energy-integrating, single-photon counting, and future energy-sensitive x-ray imaging sensors. The applicability of this linear system analysis is restricted to the tasks of low-contrast object detection in radiography. The method for scaling the figure of merit to take into consideration broad-spectrum conditions is applied to mammography for future energy-dependent detectors. An approximation valid in the typical mammographic x-ray energy range is used to calculate the broad-spectrum generalized detective quantum efficiency at zero spatial frequency, for several mammographic x-ray spectra. X-ray energy weighting in mammography is investigated in the context of simulated tumors and microcalcifications detection by comparing this figure of merit, calculated for different detector technologies, under ideal imaging conditions, at zero spatial frequency.

Theoretical analysis of the effect of charge-sharing on the Detective Quantum Efficiency of single-photon counting segmented silicon detectors

“…related to energy weighting. DQE formulations taking this effect into consideration in the spatial frequency domain have already been developed by the author [13].…”

“…This is different from "energy integrating detectors" such as phosphor-CCD assemblies or flat-panel detectors where the signal produced by an X-ray in the detector is proportional to its energy. The "energy weighting function" of a detector was introduced in a zero-frequency DQE model [12] and in a spatial-frequency dependent DQE model [13].…”

X-ray interaction characteristic functions in semiconductor detectors

“…The development of photon-counting detectors (PCDs) with energy-resolving capability is of great interest in x-ray radiology [1][2][3]. Expected benefits include improved contrast of specific materials (e.g., iodine) with the development of energy-weighting algorithms [4,5], and improved signal-tonoise ratio (SNR) performance using energy thresholds to reject electronic noise [6][7][8].…”