Randomly Accessible Active Pixel Sensor With Logarithmic-Exponential Response Enabling Low Dose and Wide Dynamic Range Indirect-Conversion X-Ray Imaging

Active pixel sensor (APS) outperforms passive pixel sensor (PPS) in sensitivity and frame rate, and although dominates in CMOS technology, has not yet been adopted in thin-film transistor (TFT)-based flat-panel X-ray detectors (FPDs) for medical imaging due to low fill factor, leading to reduced sensitivity. In this work, a novel APS with a logarithmic-exponential response based on two dual-gate TFTs is proposed and intended for high-performance large-area indirect-conversion X-ray imaging. Leveraging the in-pixel TFT amplifier, the pixelated sensor demonstrates a low off current of $\sim 10^{-{12}}$ A, a high gain of over 4% $\times 10^{{5}}$ %, a high responsivity of $10^{{5}}$ A/W, and a wide dynamic range (DR) of over 120 dB at 550 nm with a detection limit of 200 pW/cm2. Such an architecture leads to a randomly accessible 75- $\mu $ m $256\times 256$ APS array with integrating a high-resolution medical-grade gadolinium oxysulfide (GOS) scintillator for low-dose indirect-conversion X-ray imaging, requiring high resolution, wide DR, and high frame rate for low-dose mammographic imaging.