Sci—Fri AM(1): Imaging—01: Characterization of an Avalanche Detector for Low‐Dose X‐Ray Imaging

Medical procedures such as cardiac catheterization, angiography and the deployment of endovascular devices are routinely performed using x‐ray fluoroscopy, in which each image is obtained at very low x‐ray exposures. The imaging performance of current flat panel detectors (FPD) is compromised by electronic noise at these low detector exposures (0.1–10 μR/frame). There is thus a clear need to develop an imaging detector with the quantum noise limited operation of an x‐ray image intensifier and the inherent advantages of a compact solid‐state device. Here we propose a technology that takes advantage of avalanche multiplication of charge in amorphous selenium (a‐Se). To determine whether this technology holds promise for next‐generation FPDs, we investigate the following: (1) leakage currents at high electric fields, (2) real‐time imaging capability and linearity, and (3) the compliance with low‐voltage image readout electronics. Our avalanche x‐ray detector shows avalanche gains exceeding [formula omitted], and leakage currents of only [formula omitted]. The detector has a voltage‐programmable avalanche gain and can be operated in a linear regime at 30 frames per second over a five order of magnitude x‐ray exposure range, including the lowest clinical exposures encountered in fluoroscopy. Furthermore it is compatible with existing thin film transistor technology on which current FPDs are based. This detector technology should enable the development of next‐generation dose‐efficient FPDs for interventional radiology as well as advanced applications such as cone‐beam computed tomography or tomosynthesis. Combined with techniques such as region‐of‐interest fluoroscopy, this detector technology could significantly reduce radiation dose to the patient and physician.