X-ray detector with on-pixel amplification for large area diagnostic medical imaging

The most widely used pixel architecture is a passive pixel sensor (PPS) where the pixel consists of a detector and an amorphous silicon (a-SI) thin-film transistor (TFT) readout switch. While the PPS has the advantage of being compact and amenable towards high-resolution imaging, the column charge amplifiers add a large noise component to the PPS that reduces the minimum readable sensor input signal. The authors investigate a prototype current-mediated, active pixel sensor (C-APS) X-ray detection array for diagnostic medical imaging applications. Preliminary tests indicate linear performance, and a programmable circuit gain via choice of supply voltage and sampling time. In addition, the performance of GAPS amplified pixels is examined from both a-Si TFT metastability and noise performance perspectives. Theory and measurements indicate that the GAPS pixel architecture is promising for diagnostic medical imaging modalities including low-noise, real-time fluoroscopy.