Detective quantum efficiency of photon-counting x-ray detectors

Area of Science:

• Medical Imaging Physics
• X-ray Detector Technology
• Quantum Imaging

Background:

• Single-photon-counting (SPC) x-ray imaging offers enhanced image quality and energy-dependent capabilities.
• Achieving optimal image quality necessitates maximizing detective quantum efficiency (DQE) in SPC detectors.
• Existing frameworks require extension to fully characterize DQE in complex SPC systems.

Purpose of the Study:

• To develop a comprehensive description of DQE for SPC detectors utilizing adaptive binning.
• To extend the cascaded-systems analysis (CSA) framework for SPC detector DQE assessment.
• To provide a theoretical basis for optimizing SPC detector performance.

Main Methods:

• Applied the CSA framework to propagate the probability density function (PDF) of image-forming quanta.
• Developed new relationships for PDF transfer through serial and parallel cascades, accounting for scatter reabsorption.
• Modeled hypothetical silicon and selenium-based SPC detectors, including photoelectric and Compton interactions, charge collection, and electronic noise.

Main Results:

• Depth-dependent charge collection can broaden photopeaks, reducing DQE at lower x-ray energies (20-45 keV).
• Reabsorption of scattered photons can lead to double-counting events, potentially inflating signal-to-noise ratio and overestimating DQE.
• The study identified critical parameters influencing DQE, including secondary conversion gain and detector material properties.

Conclusions:

• The CSA approach was successfully extended to model signal and noise propagation in SPC detectors.
• Achieving high-performance SPC systems depends on optimizing secondary conversion gain, charge collection, electronic noise, and reabsorption characteristics.
• This work provides a framework for understanding and improving DQE in advanced x-ray imaging systems.