Experimental characterization of a direct conversion amorphous selenium detector with thicker conversion layer for...

Area of Science:

• Medical Imaging
• Radiology
• Materials Science

Background:

• Dual-energy contrast-enhanced imaging aids in breast cancer detection by identifying angiogenesis.
• Iodinated contrast agents require X-ray energies > 33 keV.
• Conventional amorphous selenium (a-Se) detectors have low absorption efficiency at these higher energies.

Purpose of the Study:

• To evaluate a prototype direct conversion flat-panel imager with a thicker a-Se layer for dual-energy contrast-enhanced breast imaging.
• To assess the impact of increased a-Se thickness on imaging performance in a digital breast tomosynthesis (DBT) system.

Main Methods:

• Spatial-frequency domain image quality metrics were used.
• Performance was evaluated for dual-energy imaging in both FFDM and DBT modes.
• Key metrics included spatial resolution, noise, detective quantum efficiency (DQE), and temporal performance.

Main Results:

• Zero-frequency DQE improved by ~20% for higher energy beams with the thicker a-Se detector.
• Increased photoconductor thickness led to a greater spatial resolution decrease with oblique X-ray entry, particularly in DBT.
• Focal spot motion also degraded spatial resolution; temporal performance was comparable to conventional detectors.

Conclusions:

• Increasing a-Se thickness enhances performance for dual-energy contrast-enhanced breast imaging.
• While oblique X-ray incidence impacts spatial resolution, image reconstruction algorithms may mitigate this effect.
• Improved DQE for high-energy X-rays outweighs potential spatial resolution degradation.