X-ray

An X-ray photograph of a person's lungs.

X-radiation is a kind of electromagnetic radiation. X-rays are waves of X-radiation. They have a shorter wavelength, and therefore more energy, than ultraviolet radiation. X-rays have a much shorter wavelength than visible light (the light that we can see). Radiation with shorter wavelengths (more energy) than the X-ray is called Gamma radiation (γ-rays). These are all parts of the electromagnetic spectrum.

The wavelength of X-rays covers a wide range. Most X-rays have a wavelength in the range of 0.01 to 10 nanometres. This corresponds with frequencies in the range 30 petahertz to 30 exahertz (3×10¹⁶ Hz to 3×10¹⁹ Hz) and energies in the range 100 eV to 100 keV.

X-rays can go through many solid materials. For this reason, taking photograms with X-rays is used in medicine in order to see bones and other things inside the body. Sometimes the term "X-ray" means these pictures instead of the radiation that makes them.

What these images show will depend on three things: Rayleigh scattering, Compton scattering and photoabsorption.^[1]^[2]^[3] The images show bone because it is dense enough that X-rays are not able to pass through it. Instead, the X-rays are either absorbed or scattered. The images do not show skin and muscle, however, because these tissues are transparent enough for the X-rays to pass through them without being absorbed too much. To detect tumors, other imaging devices are used; such as magnetic resonance imaging. A computed tomography scanner combines an X-ray machine and computer to construct a three dimensional (3D) picture. This has some ability to see other things besides bone.

X-rays are made by hitting metal with fast-moving electrons. They are photons, tiny packets of energy that can move atoms and change chemicals in the body. They are ionizing radiation but the things they do depend on the wavelength of the X-rays (or how much energy they have). X-rays with smaller energies ("soft" x-rays) cause the photoelectric effect. Mid-level energies cause Compton scattering. High-level energies ("hard" X-rays) cause pair production. X-rays used for making pictures of people have low to medium energy. Radiation therapy that treats cancer uses Compton scattering and sometimes Pair production.

There are small amounts of X-rays in the air. Like other energy in the air, X-rays can change living cells. Exposing the human body to high doses of X-rays for a long time is dangerous. It can cause cancer. However, cancer cells are hurt more easily, so X-rays are sometimes used to kill them.

X-ray Media

Natural color X-ray photogram of a wine scene. Note the edges of hollow cylinders as compared to the solid candle.
William Coolidge explains medical imaging and X-rays.
Example of a Crookes tube, a type of discharge tube that emitted X-rays
Wilhelm Conrad Röntgen
Hand mit Ringen (Hand with Rings): print of Wilhelm Röntgen's first "medical" X-ray, of his wife's hand, taken on 22 December 1895 and presented to Ludwig Zehnder of the Physik Institut, University of Freiburg, on 1 January 1896
Taking an X-ray image with early Crookes tube apparatus, late 1800s. The Crookes tube is visible in center. The standing man is viewing his hand with a fluoroscope screen. The seated man is taking a radiograph of his hand by placing it on a photographic plate. No precautions against radiation exposure are taken; its hazards were not known at the time.
Surgical removal of a bullet whose location was diagnosed with X-rays (see inset) in 1897
Images by James Green, from "Sciagraphs of British Batrachians and Reptiles" (1897), featuring (from left) Rana esculenta (now Pelophylax lessonae), Lacerta vivipara (now Zootoca vivipara), and Lacerta agilis
1896 plaque published in "Nouvelle Iconographie de la Salpetrière", a medical journal. In the left a hand deformity, in the right same hand seen using radiography. The authors named the technique Röntgen photography.
A patient being examined with a thoracic fluoroscope in 1940, which displayed continuous moving images. This image was used to argue that radiation exposure during the X-ray procedure would be negligible.

Related pages

References

↑ "RTAB: the Rayleigh scattering database". Lynn Kissel. 2000-09-02. Archived from the original on 2011-12-12. Retrieved 2012-11-08.
↑ David Attwood (1999). "3". Soft X-rays and extreme ultraviolet radiation. Cambridge University Press. ISBN 978-0-521-65214-8. Archived from the original on 2011-04-12. Retrieved 2013-10-30.
↑ Jerrold T. Bushberg, J. Anthony Seibert, Edwin M. Leidholdt, and John M. Boone (2002). The essential physics of medical imaging. Lippincott Williams & Wilkins. p. 38, 42. ISBN 978-0-683-30118-2.{{cite book}}: CS1 maint: multiple names: authors list (link)

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[1] "RTAB: the Rayleigh scattering database". Lynn Kissel. 2000-09-02. Archived from the original on 2011-12-12. Retrieved 2012-11-08.

[2] David Attwood (1999). "3". Soft X-rays and extreme ultraviolet radiation. Cambridge University Press. ISBN 978-0-521-65214-8. Archived from the original on 2011-04-12. Retrieved 2013-10-30.

[3] Jerrold T. Bushberg, J. Anthony Seibert, Edwin M. Leidholdt, and John M. Boone (2002). The essential physics of medical imaging. Lippincott Williams & Wilkins. p. 38, 42. ISBN 978-0-683-30118-2.{{cite book}}: CS1 maint: multiple names: authors list (link)

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