X-ray inspection systems play a critical role in many non-destructive testing and security applications, with systems typically measuring attenuation during transmission along straight-line paths connecting sources and detectors. Computed tomography (CT) systems can provide higher-quality images than single- or dual-view systems, but the need to measure many projections through the scene increases system complexity and cost. We seek to maximize the image quality of sparse-view (few-view) systems by combining attenuation data with measurements of Compton-scattered photons, that deflect after scattering and arrive at detectors via broken ray paths that provide additional sampling of the scene. The work below presents experimental validation of a singlescatter forward model for Compton-scatter data measured with energy-resolving detectors, and demonstrates a reconstruction algorithm that combines both attenuation and scatter measurements. The results suggest that including Compton-scattered data in the reconstruction process can improve image quality for few-view systems.
The purpose of this paper is to provide a performance characterization of a new large field-of-view (LFOV) flat panel detector with a novel pixel design that has been optimized for both screening mammography and low dose advanced applications such as tomosynthesis. The measurements reported here were performed on prototype x-ray imagers for GE's upcoming LFOV mammography system. In addition to a light sensitive photodiode and a field effect transistor (FET), a storage capacitor has been added to each pixel in order to increase the dynamic range. In order to characterize the performance of the detector, measurements of the MTF, noise power spectrum, DQE, electronic noise, conversion factor, and lag were made. The results show that the new detector can deliver a DQE at 0 and 5 lp/mm of 72% and 28% while maintaining an MTF at 5 lp/mm of 30%. The addition of a storage capacitor at each pixel allows the conversion factor to be increased to reduce the noise floor - leading to a 400% extension of the dynamic range. Finally, a re-design of the FET and photodiode to reduce the time constants allows a 10X reduction in the lag that enables up to 4 frame per second imaging with less than 1% lag. This work represents the first results from a next generation large field of view a Si/CsI based x-ray imager for mammography and shows that a single detector can achieve high performance standards for both high dose screening and low dose, fast acquisition tomosynthesis simultaneously.
We report on a set of tests that measure the performance of a-Si flat panel TFT arrays used in digital x-ray detectors. During production of high performance TFT panels for applications such as mammography it is important to verify the integrity and quality of the TFT array at progressive stages of production. Early identification of failing TFT arrays as well as continuous monitoring of the production process can result in early termination of poor quality panels, quick identification of the root cause of failures, and correction of process drift to prevent failures from occurring. We present results of a system designed to test the performance of a-Si TFT arrays during the production process. Metrics which are important to x-ray image quality were tested, including FET performance, pixel capacitance, storage capacitor lag and diode leakage. Functional tests were performed entirely on pixels in the imaging array using timing and biasing conditions that mimic x-ray illumination.