An X-ray machine utilizes electromagnetic radiation to produce an image of an object, usually with the purpose of visualizing something located below the object's surface. A medical x-ray machine is made up of an X-ray source or X-ray tube, an x-ray detection system, and positioning hardware to align these two components with the object to be imaged.
How They Work
A medical x-ray imaging system consists of an X-ray source or X-ray generator, and an image detection system which can either be comprised of film (analog technology) or a digital capture system
X-ray Sources
In the typical X-ray source of less than 450 kV, X-ray photons are produced by an electron beam striking a target. The electrons that make up the beam are emitted from a heated cathode filament. The electrons are then focused and accelerated towards an angled anode target. The point where the electron beam strikes the target is called the focal spot. Most of the kinetic energy contained in the electron beam is converted to heat, but around 10% of the energy is converted into X-ray photons, the excess heat is dissipated via a heat sink. At the focal spot, X-ray photons are emitted at 180deg from the target surface, the highest intensity being around 60deg to 90deg there is a small round window in the X-ray tube directly above the angled target. This window allows the X-ray to exit the tube with little attenuation while maintaining a vacuum seal required for the X-ray tube operation. X-ray machines work by applying controlled voltage, current, and time to the X-ray tube, which results in a beam of X-rays. The beam is projected on matter. Some of the X-ray beam will pass through the object, while some are reflected. The resulting pattern of the radiation is then ultimately detected by a detection medium including rare earth screens (which surround photographic film), semiconductor detectors, or X-ray image intensifiers.
X-Ray Detection
In healthcare applications in particular, the x-ray detection system rarely consists of the detection medium. For example, a typical stationary radiographic x-ray machine also includes an ion chamber and grid. The ion chamber is basically a hollow plate located between the detection medium and the object being imaged. It determines the level of exposure by measuring the amount of x-rays that have passed through the electrically charged, gas-filled gap inside the plate. This allows for minimization of patient radiation exposure by both ensuring that an image is not underdeveloped to the point the exam needs to be repeated and ensuring that more radiation than needed is not applied. The grid is usually located between the ion chamber and object and consists of several lead slats stacked next to each other (resembling open window blinds). In this manner, the grid allows straight x-rays to pass through to the detection medium but absorbs reflected x-rays. This improves image quality by preventing reflected (non-diagnostic) x-rays from reaching the detection medium allowing for lower exam doses overall. Images taken with such devices are known as X-ray photographs or radiographs.

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