Linear energy transfer

The quotient of [math]dE[/math] by [math]dl[/math], where [math]dE[/math] is the mean energy lost by the charged particle due to electronic interactions in traversing a distance [math]dl[/math], thus:

[math] L = \frac{dE}{dl} [/math]

The unit of linear energy transfer is joule per metre J m^-1, often given in keV μm^-1.

High LET radiation: Radiation with capacity, by its own or by the secondary radiations it generates, of linear energy transfer higher than around 10 keV μm^-1. Normally high LET radiation is assumed to include protons, neutrons and alpha particles (or other particles of similar or greater mass) except for protons having energies greater than around 4 MeV.

Low LET radiation: Radiation with low linear energy transfer (LET), normally assumed to comprise photons (including X rays and gamma radiation), electrons, positrons and muons. High energy (>4 MeV) protons are considered to be a low LET radiation.

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