The detective quantum efficiency (DQE) is widely accepted as a primary measure of x-ray detector performance
in the scientific community. A standard method for measuring the DQE, based on IEC 62220-1, requires the
system to have a linear response meaning that the detector output signals are proportional to the incident x-ray
exposure. However, many systems have a non-linear response due to characteristics of the detector, or post
processing of the detector signals, that cannot be disabled and may involve unknown algorithms considered
proprietary by the manufacturer. For these reasons, the DQE has not been considered as a practical candidate
for routine quality assurance testing in a clinical setting. In this article we described a method that can be used
to measure the DQE of both linear and non-linear systems that employ only linear image processing algorithms.
The method was validated on a Cesium Iodide based flat panel system that simultaneously stores a raw (linear)
and processed (non-linear) image for each exposure. It was found that the resulting DQE was equivalent to
a conventional standards-compliant DQE with measurement precision, and the gray-scale inversion and linear
edge enhancement did not affect the DQE result. While not IEC 62220-1 compliant, it may be adequate for QA
A new method of measuring the zero-frequency value of the detective quantum efficiency (DQE) of x-ray detectors is described. The method is unique in that it uses what we call a "simulated neutral-attenuator" method to determine the system gain derived from image-based measurements of x-ray transmission through a thin copper foil of known thickness. Since this method uses only low-contrast image structure, it is a true measure of the "small-signal" system gain which is assumed piece-wise linear. A theoretical expression is derived for the linearized pixel value which is the pixel value that a linear system would have for the test conditions. Combining this with the measured detector exposure and zero-frequency value of the Wiener noise power spectrum provides the DQE. It is shown this method gives a DQE value that is in agreement with conventional test methods on a linear flat-panel detector, and that the same DQE value is obtained when using both raw (linear) and processed (non-linear) images.