Direct-Conversion X-Ray Detector with 50-µm High-Gain Pixel Amplifiers for Low-X-Ray-Dose Digital Mammography

摘要: This study proposes an active pixel sensor (APS) design for readout signal amplification to replace the traditional passive (PPS) design. The APS adds only one extra thin-film transistor (TFT) amplifier, giving it high sensitivity of architecture and spatial resolution PPS architecture. mobility amorphous silicon (a-Si) TFT is 0.56 cm2/Vs, circuit more than 10×, on/off current ratio 107, leakage on order 1 fA. A 200-µm-thick layer selenium (a-Se) as X-ray photoconductor was deposited array with 160 × pixels various sizes, down 50 µm. 40-kVp spectra obtained tube currents 40 mA, respectively, were used measuring gray-level contrast induced by X-rays. experimental results show that contrasts 50-µm 5.57 ± 0.89 13.19 1.94 those 70-µm 15.94 2.98 24.19 2.76 under exposure at respectively.