50 μm pixel pitch wafer-scale CMOS active pixel sensor x-ray detector for digital breast tomosynthesis

Area of Science:

• Medical Imaging
• Semiconductor Devices
• X-ray Detection

Background:

• Wafer-scale CMOS active pixel sensors (APSs) are emerging for x-ray imaging.
• Their small pixel pitch and low noise are advantageous for medical applications like digital breast tomosynthesis (DBT).

Purpose of the Study:

• To experimentally and theoretically evaluate the imaging performance of the DynAMITe CMOS APS x-ray detector.
• To assess its suitability for medical imaging, particularly DBT, by analyzing key imaging properties and microcalcification detectability.

Main Methods:

• Developed a modified cascaded system model for CMOS APS x-ray detectors, incorporating nonlinear signal and noise properties.
• Experimentally measured and modeled imaging properties including modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE).
• Calculated image signal-to-noise ratio (SNRi) for microcalcifications at various mean glandular doses (MGD).

Main Results:

• The DynAMITe detector achieved high spatial resolution (10 mm⁻¹) and a DQE of approximately 0.5 at low spatial frequencies (<1 mm⁻¹).
• Modeling indicated that 165 μm microcalcifications could be distinguished with a 27% lower MGD compared to the clinical standard (~1.3 mGy) for an average breast.
• Detection of 100 μm microcalcifications may require further detector, acquisition, and reconstruction optimizations.

Conclusions:

• The DynAMITe CMOS APS x-ray detector demonstrates excellent imaging properties suitable for medical applications like DBT.
• The developed nonlinear cascaded system model accurately predicts detector performance and aids in dose optimization for microcalcification detection.
• Further advancements are needed to enhance the detection of smaller microcalcifications, suggesting future research directions in detector technology and imaging techniques.