Flexible X-ray Detector for Automatic Exposure Control in Digital Radiography

Automatic Exposure Controllers (AEC), currently used in diagnostic radiation imaging, reduce the rate of re-imaging by controlling the radiation exposure in the image acquisition areas while obtaining optimal diagnostic image. Among several types of AEC chamber, ionization chamber and solid state detector are commonly used. Especially, solid state detector makes AEC chamber be thin by minimizing the thickness to below 3 mm and show superior performance in application requiring high field signal during low X-ray energy exposure around 40 keV. However, commercially used solid state detector made of silicon diode suffer from ineffective performance changes due to doping variations and mechanically fragile property. In this study, solid state detectors made of compound photoconductive nanoparticles were introduced to detect X-ray signals. Three kinds of detectors were fabricated by depositing HgI2 with 14 mu m thickness, PbI2 with 11 mu m thickness, and PbO with 14 mu m thickness photoconductive layers using a screen printing method. X-ray linearity, reproducibility, transmittance, and energy dependence, and bending tests performed using these detectors yielded results close to current AEC chambers. In addition, from the result of bending test, the detector fabricated by the particle in binder method showed mechanically uncrushable and stable properties due to flexible property of binder material. These results point to the feasibility of photoconductor-based AEC chambers in the fields of diagnostic radiation and other areas.