A liquid cathode for medical imaging X-ray sources

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PROJECT SUMMARY It is generally agreed that the development of distributed X-ray sources (i.e., systems having multiple X-ray sources contained within a single vacuum envelope) could fundamentally improve tomographic medical X-ray imaging technology by removing the need for mechanical motion of the X-ray source. Removing such motion provides the potential to develop more compact, higher-speed, and lower-cost X-ray imaging systems with better image quality, new imaging modalities, and more widespread system availability. The net result would be to make imaging systems with greater capabilities more widely available to a larger number of people. A significant impediment to achieving this result has been the lack of an appropriate cathode (electron emitter) technology for the distributed X-ray source. This grant application proposes to explore a very different approach to cathodes for medical X-ray imaging sources: a liquid cathode. This unique cathode uses an electrohydrodynamic instability to form field electron emitting sites on the surface of a liquid metal with Faraday waves, induced by slight mechanical vibration of the fluid by a piezoelectric transducer. Because the cathode is a liquid, it is self-healing, which will mitigate failure mechanisms associated with field emission cathodes used to date, thereby resulting in high reliability and long life. By distributing the resulting compact electron source elements in space, the X-ray focal spot distribution can be changed, i.e., reconfigured electronically, in real time. This approach has the potential to shift the paradigm of medical X-ray imaging systems by combining a reliable, long-lived, and robust source with an electronically reconfigurable X-ray focal spot distribution. The specific aims of this proposal focus on experiments to determine whether the liquid cathode approach has the performance characteristics required for medical imaging applications. The aims are: Aim 1. Fabricate liquid cathode testbed Aim 2. Quantify electron emission characteristics of liquid cathode Aim 3. Quantify X-ray emission characteristics of liquid cathode-based source Aim 4. Develop preliminary liquid cathode-based designs for several widely used medical imaging applications