Field Emission Arrays for Tomographic Medical X-Ray Imaging

X-ray imaging has been important to both medical and industrial applications for over 100 years. Tomographic X-ray imaging has evolved over the last several decades with improvements in x-ray detectors and computing capability. The ability to reconstruct high-resolution, three-dimensional anatomical images for the detection of tumors, blood clots, and bleeding has had a major impact in medicine. Tomographic imaging requires that the X-ray source and/or detector be moved relative to the object to be imaged. Conventional computed tomography (CT) involves rotation about, and translation along, the object. Another methodology is scanned electron beam systems, which have seen limited implementation in medical imaging due to their complexity and size. An alternative approach is to use microfabricated cold field emission array cathodes to provide a stationary X-ray source for CT or digital tomosynthesis. The use of multiple sources circumvents the technically demanding need for X-ray tube motion, thereby simplifying the imaging system and providing the potential for increased imaging speed. Combining a matrix-addressable flat-panel X-ray source with existing flat-panel digital detector technology would allow for the construction of simple and compact tomographic imaging systems for use in a wide variety of medical, industrial, and security applications. In this presentation we report results demonstrating the feasibility of using microfabricated cold cathode field electron emission cathodes as stationary X-ray sources for tomographic medical imaging. Electron beam currents of 25 mA at voltages of 25 to 30 kV have been used to produce x-ray source spot diameters of 250 mum. Analysis of both filtered and unfiltered X-ray spectra from molybdenum anodes show clear characteristic X-ray lines. These X-ray source characteristics are consistent with the requirements for human breast imaging