K-absorption edge
Citation, DOI, disclosures and article data
Citation:
Vajuhudeen Z, Bell D, Murphy A, K-absorption edge. Reference article, Radiopaedia.org (Accessed on 27 Mar 2025) https://doi.org/10.53347/rID-79625
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rID:
79625
Article created:
1 Jul 2020,
Zemar Vajuhudeen
Disclosures:
At the time the article was created Zemar Vajuhudeen had no recorded disclosures.
View Zemar Vajuhudeen's current disclosures
Last revised:
Disclosures:
At the time the article was last revised Daniel J Bell had no financial relationships to ineligible companies to disclose.
View Daniel J Bell's current disclosures
Revisions:
6 times, by
3 contributors -
see full revision history and disclosures
Systems:
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Synonyms:
- K-edge
- K-absorption edges
The K-absorption edge (K-edge) refers to the abrupt increase in the photoelectric absorption of x-ray photons observed at an energy level just beyond the binding energy of the k-shell electrons of the absorbing atom.
K-shell binding energies are specific to each element. As the atomic number (Z) of an element increases, so does its corresponding k-shell binding energy, and therefore the greater the photon energy at which the K-edge occurs. Binding energies are expressed in kiloelectronvolts (keV).
The most abundant elements in human tissue (hydrogen, carbon, oxygen, nitrogen) have K-edges that are too low to be detectable (<1 keV).
Elements with larger K-edge values, that are within the useful portion of the x-ray spectrum, are of greater interest in radiology. The k-edge properties of certain materials can be specifically chosen for their use in contrast media, intensifying screens and beam filters.
For example:
iodine (Z = 53, K-edge = 33.2 keV) is commonly used as a contrast agent in radiography
molybdenum (Z = 42, K-edge = 20.0 keV) is commonly used as a beam filter in mammography
References
- 1. Jiang Hsieh. Computed Tomography Principles, Design, Artifacts, and Recent Advances. (2009) ISBN: 9780470563533 - Google Books
- 2. Penelope Allisy-Roberts, Jerry R. Williams. Farr's Physics for Medical Imaging. (2007) ISBN: 9780702028441 - Google Books
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