1 research outputs found
A framework for performance characterization of energy-resolving photon-counting detectors
Photon-counting energy resolving detectors are subject to intense research
interest, and there is a need for a general framework for performance
assessment of these detectors. The commonly used linear-systems theory
framework, which measures detector performance in terms of noise-equivalent
quanta (NEQ) and detective quantum efficiency (DQE) is widely used for
characterizing conventional X-ray detectors but does not take energy-resolving
capabilities into account. We extend this framework to encompass
energy-resolving photon-counting detectors and elucidate how the imperfect
energy response of real-world detectors affects imaging performance. We
generalize NEQ and DQE to matrix-valued quantities as functions of spatial
frequency, and show how these can be calculated from simple Monte Carlo
simulations. To demonstrate how the new metrics can be interpreted, we compute
them for simplified models of fluorescence and Compton scatter in a
photon-counting detector and for a Monte Carlo model of a CdTe detector with
0.5 x 0.5 mm^2 pixels. Our results show that the ideal-linear-observer
performance for any detection or material quantification task can be calculated
from the proposed metrics. Off-diagonal elements in these matrices are shown to
be related to imperfect energy resolution. The Monte Carlo model of the CdTe
detector predicts a zero-frequency dose efficiency relative to an ideal
detector of 0.86 and 0.65 for detecting water and bone, respectively. When the
task instead is to quantify these materials, the corresponding values are 0.34
for water and 0.26 for bone. We have shown that the matrix-valued NEQ and DQE
metrics contain sufficient information for calculating the dose efficiency for
both detection or quantification tasks, the task having any spatial and energy
dependence. This framework will be beneficial for the development of
photon-counting X-ray detectors.Comment: The final version was published in Medical Physics Correction made in
proof: Just before Eq. 20, "an ideal detector" should be "a detector that is
purely photon-counting (i.e. does not measure photon energy) but ideal in all
other respects