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A Stationary Computed Tomography Module Using Photocathode-Driven X-Ray Sources

A Cramer1,2* , J Hecla1 , D Wu2,3 , X Lai2,3 , K Yang2,3 , T Moulton3 , S Kenyon4 , Z Arzoumanian4, W Krull3 , K Gendreau4 , R Gupta2,3 , (1) Massachusetts Institute of Technology, Cambridge, MA, (2) Harvard Medical School, Boston, MA, (3) Massachusetts General Hospital, Boston, MA, (4) NASA's Goddard Space Flight Center, Greenbelt, MD.


(Monday, 7/30/2018) 7:30 AM - 9:30 AM

Room: Karl Dean Ballroom A1

Purpose: 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. A CT system that is significantly lighter weight and cheaper, and operates without any moving parts, could expand access to volumetric x-ray imaging to rural communities, battlefield care, and extended space missions.

Methods: We have designed a stationary x-ray tomography module containing multiple miniature x-ray sources. As part of this system, we present a novel photocathode-based x-ray source, created by depositing a thin film of magnesium on an electron multiplier. When illuminated by a UV LED, this photocathode emits a beam of electrons, with a maximum beam current of up to 500 uA per multiplier. The produced electrons are then accelerated through a high voltage to a tungsten or molybdenum target. These sources are individually addressable and can be pulsed rapidly, through electronic control of the LEDs. The output current can be controlled by adjusting the luminance of the LEDs. The sources can survive exposure to atmospheric pressure. Seven of these sources comprising a 17.5 degree arc are housed together within a custom vacuum manifold. This module (excluding the vacuum pump) weighs approximately 1 kilogram. A ring or arc of these modules could be used for tomographic imaging.

Results: By turning the sources on and off one after another in series, we are able to perform limited-angle x-ray tomography without any moving parts. With a clinical flat-panel detector, we acquired 3D reconstructions of several biological samples.

Conclusion: We demonstrate a modular and highly portable design for volumetric x-ray imaging, and the utility of a metallic photocathode as the electron generation method for medical x-ray production.


Tomography, X-ray Production, Tomosynthesis


IM- CT: Development (New technology and techniques)

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