| Summary: | Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018. === Cataloged from PDF version of thesis. === Includes bibliographical references (pages 71-77). === Computed tomography (CT) is the clinical standard for diagnosing many emergent medical conditions, such as stroke and traumatic brain injuries. Unfortunately, the size, weight, and expense of CT systems make them inaccessible for patients outside of large trauma centers. We have designed a module containing multiple miniature x-ray source that would allow for CT scanners to be significantly lighter weight and cheaper, and to operate without any moving parts. This could expand access to this valuable diagnostic tool to rural and low-income communities, emergency medicine, battlefield care, and extended space missions. As part of this system, we present a photo-cathode-based x-ray source, created by depositing a thin film of magnesium on an electron amplifier. When illuminated by a UV LED, this photocathode emits a beam of electrons, with a maximum beam current of up to 500 uA per amplifier. The produced electrons are then accelerated through a high voltage to a tungsten target. These sources are individually addressable and can be pulsed rapidly, through electronic control of the LEDs. Seven of these sources comprising a 17.5 degree arc are housed together within a custom vacuum manifold. A full ring of these modules could be used for CT imaging. By turning the sources on and off one after another in series, we are able to demonstrate limited-angle x-ray tomography without any moving parts. With a clinical flat-panel detector, we demonstrate 3D reconstructions of several biological samples. === by Avilash Cramer. === S.M.
|
|---|
