Linear energy transfer

Last revised by Daniel J Bell on 24 Apr 2022

Linear energy transfer (LET) is the average (radiation) energy deposited per unit path length along the track of an ionizing particle. Its units are keV/μm.

Linear energy transfer describes the energy deposition density of a particular type of radiation, which largely determines the biological consequence of radiation exposure.

The linear energy transfer of a charged particle 2 is ∞ Q​2/Ek

  • linear energy transfer is proportional to the square of the charge of the particle (Q2)
  • linear energy transfer is inversely proportional to the particle's kinetic energy (Ek)
High linear energy transfer radiations: linear energy transfer 3-200 keV/μm
  • commonly mediated by:
  • greater density of interactions at cellular level
  • more likely, than low linear energy transfer, to produce biological damage in a given volume of tissue

Low linear energy transfer radiations: linear energy transfer 0.2-3 keV/μm
  • commonly mediated by:
  • less likely than high linear energy transfer to produce tissue damage in the same volume of tissue

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