Low-Cost, Low-Dose Flat Panel X-ray Detectors with a Novel Semiconductor

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Project Summary/Abstract After decades of advances in medical imaging, X-ray based imaging modalities are still the backbone of modern general and targeted diagnostic and therapeutic imaging. With the advent of flat panel detector technology, flat panel X-ray imagers (FPXIs) are now widely used in digital radiography, fluoroscopy, digital tomosynthesis, image-guided radiation therapy, and cone beam computed tomography. The majority of commercial FPXIs are based on scintillators and rely on indirect conversion of X-rays to photons and then to electronic signals, and a smaller portion is based on amorphous selenium (a-Se) semiconductor films that directly convert absorbed X- rays to an electronic signal. The indirect FPXIs have high detective quantum efficiency (DQE) over the energy range of interest (up to 140kVp) and are used in most of the flat panel imaging applications. However, the isotropic propagation of light in the scintillators adversely affects the quality of obtained images, and high radiation doses are needed to obtain images with acceptable brightness and contrast. On the other hand, a-Se based direct-conversion panels have excellent spatial resolution and DQE, but only up to 40kVp, due to low absorptivity of a-Se at higher energies. Thus, the use of direct-conversion FPXIs is currently limited only to soft- tissue applications, primarily mammography. In this program, we will develop direct-conversion FPXIs with a novel semiconductor sensor with high sensitivity at X-ray energies up to 140kVp. In Phase I, the feasibility of this semiconductor X-ray sensor was evaluated and excellent results in terms of sensitivity, response linearity, charge transport properties, and stability were obtained. The Phase II program is focused on demonstration of X-ray imagers based on the novel sensor, including large area FPXIs suitable for transitioning to clinical testing, and scalable X-ray scanner modules suitable for medical, scientific research, and industrial imaging applications.