Your continued donations keep Wikipedia running!    

X-ray machine

From Wikipedia, the free encyclopedia

Jump to: navigation, search
Bertha Röntgen's hand, one of the first X-ray images.
Bertha Röntgen's hand, one of the first X-ray images.

An X-ray machine is a machine used to produce X-rays via X-ray tubes. These machines are designed to generate artificial (human-made) X-ray photons on demand.

Contents

[hide]

History

Hermann von Helmholtz formulated mathematical equations for X-rays. Physicist Johann Hittorf observed tubes with energy rays extending from a negative electrode. William Crookes investigated the effects of energy discharges on rare gases. Heinrich Hertz began experimenting and demonstrated that cathode rays could penetrate very thin metal foil (such as aluminium). In 1887, Nikola Tesla began to investigate X-rays and produced the bremsstrahlung process. In 1895, Wilhelm Röntgen began observing and further documenting X-rays while experimenting with vacuum tubes.

X-rays are produced by bombarding a surface with high speed electrons (in a vacuum). One of the first X-ray photographs was made of the hand of Röntgen's wife. The image displayed both her wedding ring and bones. On January 18, 1896 an X-ray machine was formally displayed by H.L. Smith. Upon discovery in 1895, X-Rays were advertised as the new scientific wonder and seized upon by entertainers. Circus patrons viewed their own skeletons and were given pictures of their own bony hands wearing silhouetted jewelry. While many people were fascinated by this discovery, others feared that it would allow strangers to look through walls and doors and privacy.

X-ray machines in shoe stores

In the 1940s and 50s, (real time) X-ray machines were used in stores to help sell shoes. These were known as fluoroscopes. However, as the harmful effects of X-ray radiation were properly considered, they finally fell out of use. (They were more a clever marketing tool to attract customers than a fitting aid. Shoe-fitting use of the device was first banned by the state of Pennsylvania in 1957. There was obviously a novelty attraction to children.)

How They Work

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 is stopped, or "absorbed." The resulting pattern of the radiation is then detected by rare earth screens (which surround photographic film), semiconductor detectors, or image intensifiers. Images taken with such devices are known as X-ray photographs or radiographs.

Uses

X-ray technology is used in health care for bones, security and material analysis.

Health Care

There are two basic areas in which Health Care uses X-radiation; Radiography, and Fluoroscopy.

Radiology is used for fast, highly penetrating images. Usually it's used on areas with a high bone content. Some forms of Radiography uses are Panoramic X-rays, Radiography, Mammography, Tomography, and Radiotherapy.

Fluoroscopy is used in cases where real-time visualization is necessary. You may have seen a type of fluorography at the airport. Some of the uses of Fluorography are Angiography, barium enemas, barium swallows, biopsies, and hip replacement.

X-rays are highly penetrating, ionizing radiation, and X-ray machines are used in radiology to take pictures of bones and teeth. This is because bones absorb the radiation more than the less-dense soft tissue. X-rays from a source are passed through the body and a photographic cassette; areas where radiation is absorbed show up as clear. This can be used to diagnose broken or fractured bones. Imaging of the digestive tract is done with the help of barium as a contrast medium, radiopaque medium.

Security

X-ray machines are used to screen objects non-invasively. Luggage at airports is examined for possible bombs and weapons. These machines are very low dose and safe to be around.

Advances in X-ray technology

A film of carbon nanotubes (as a cathode) that emits electrons at room temperature when exposed to an electrical field has been fashioned into an X-ray device. An array of these emitters can be placed around a target item to be scanned and the images from each emitter can be assembled by computer software to provide a 3-dimensional image of the target in a fraction of the time it takes using a conventional X-ray device. The carbon nanotube emitters also use less energy than conventional X-ray tubes leading to lower operational costs. (Zhang, et al., 2005)(http://www.unc.edu/~zhou/doc/mbfex_apl_05.pdf)

Patents

See also

References

External links

Personal tools
In other languages