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

• Published in: IEEE sensors journal 2024-11, p.1-1
• Main Authors: Li, Xianming, Wu, Weisheng, Yan, Weikang, Xie, Haorong, Liu, Xinghui, Wang, Kai
• Format: Article
• Language: English
• Subjects: active pixel sensor; Electrodes; logarithmic-exponential response; Logic gates; low dose X-ray imaging; Noise; Photonics; randomly-accessible; Sensitivity; Sensors; Thin film transistors; Thin-film transistor; Threshold voltage; Transistors; wide dynamic range; X-ray imaging
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2024.3496761

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 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 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 ~10 -12 A, a high gain of over 4×10 5 % a high responsivity of 10 5 A/W and a wide dynamic range of over 120dB at 550nm with a detection limit of 200pW/cm 2 . Such an architecture leads to a randomly-accessible 75-μm 256×256 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 dynamic range, and high frame rate for low-dose mammographic imaging.