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1. Acronym for: Kinetic Energy Released to MAtter.

2. It is the kinetic energy transferred by radiation to unit mass at a specified position.

3. Air kerma is the energy (in J) transferred to a unit mass (in Kg) of air.

4. The unit of kerma is the Gray (Gy).

5. Beam intensity is hard to measure so it is indirectly measured using the air kerma rate.

6. At diagnostic energies, kerma and absorbed dose are effectively equal.


1. Bushberg, J. T. (2012). The essential physics of medical imaging. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. Find it at Amazon
2. Heggie, J. C., Liddell, N. A., & Maher, K. P. (1997). Applied imaging technology. Melbourne: St. Vincents Hospital.

Ⓒ A. Manickam 2018

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