{"entity":{"id":"linear-energy-transfer","kind":"term","name":"Linear energy transfer (LET)","aka":["LET","linear energy transfer","high-LET","low-LET","keV/µm","keV per micrometre"],"tldr":"How densely a radiation track dumps energy along its path. Sparse tracks (X-rays, most of a proton beam) are easier to repair; dense tracks (the proton's stop-point, carbon ions, alpha particles) punch clustered holes in DNA.","summary":"Linear energy transfer is the energy a charged particle deposits per unit length of track, usually in keV per micrometre. Photons and electrons are low-LET. Protons are mostly low-LET along the entrance plateau and rise at the Bragg peak and just beyond it, which is why a constant relative biological effectiveness of 1.1 is only a reporting convention. Carbon ions and alpha particles (around 100 keV per micrometre) are high-LET: they cause clustered double-strand breaks, work in hypoxia, and are less sensitive to fraction size. LET is the physical input to relative biological effectiveness; the two are not the same number.","asOf":"2026-09-17","wikipedia":"https://en.wikipedia.org/wiki/Linear_energy_transfer","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Linear_energy_transfer"},{"label":"Paganetti, RBE values for proton beam therapy (IJROBP 2014)","url":"https://doi.org/10.1016/j.ijrobp.2014.07.001"}],"tags":["radiation-wave5"],"related":[],"cancers":[],"sections":["radiation"],"technologies":["proton-therapy","carbon-ion","imrt-igrt","targeted-alpha-therapy","bnct","intensity-modulated-proton-therapy"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["relative-biological-effectiveness","alpha-beta-ratio","alpha-vs-beta","oxygen-enhancement-ratio","bragg-peak"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"Treatment jargon"},"route":"/terms/linear-energy-transfer/","neighbours":{"section":[{"id":"radiation","kind":"section","name":"Radiation Therapy","route":"/fronts/radiation/"}],"technology":[{"id":"bnct","kind":"technology","name":"Boron neutron capture therapy","route":"/technologies/bnct/"},{"id":"carbon-ion","kind":"technology","name":"Carbon-ion therapy","route":"/technologies/carbon-ion/"},{"id":"imrt-igrt","kind":"technology","name":"IMRT / IGRT (modern external beam)","route":"/technologies/imrt-igrt/"},{"id":"intensity-modulated-proton-therapy","kind":"technology","name":"Pencil-beam scanning and intensity-modulated proton therapy","route":"/technologies/intensity-modulated-proton-therapy/"},{"id":"proton-therapy","kind":"technology","name":"Proton therapy","route":"/technologies/proton-therapy/"},{"id":"targeted-alpha-therapy","kind":"technology","name":"Targeted alpha therapy","route":"/technologies/targeted-alpha-therapy/"},{"id":"linear-quadratic-model","kind":"technology","name":"The linear-quadratic model and fractionation","route":"/technologies/linear-quadratic-model/"}],"term":[{"id":"alpha-vs-beta","kind":"term","name":"Alpha vs beta emitters","route":"/terms/alpha-vs-beta/"},{"id":"alpha-beta-ratio","kind":"term","name":"Alpha/beta ratio","route":"/terms/alpha-beta-ratio/"},{"id":"bragg-peak","kind":"term","name":"Bragg peak","route":"/terms/bragg-peak/"},{"id":"oxygen-enhancement-ratio","kind":"term","name":"Oxygen enhancement ratio","route":"/terms/oxygen-enhancement-ratio/"},{"id":"relative-biological-effectiveness","kind":"term","name":"Relative biological effectiveness (RBE)","route":"/terms/relative-biological-effectiveness/"}],"pairing":[{"id":"proton-vs-imrt","kind":"pairing","name":"Caution: proton therapy vs IMRT","route":"/pairings/proton-vs-imrt/"}],"idea":[{"id":"idea-fund-proton-coverage-with-evidence","kind":"idea","name":"Pooled coverage-with-evidence for proton therapy across all centres","route":"/ideas/idea-fund-proton-coverage-with-evidence/"},{"id":"idea-bio2-let-rbe-ab-selects-protons","kind":"idea","name":"Use LET, RBE and alpha/beta to decide when protons beat IMRT","route":"/ideas/idea-bio2-let-rbe-ab-selects-protons/"}],"paper":[{"id":"paper-paganetti-proton-rbe-ijrobp-2014","kind":"paper","name":"Paganetti 2014: proton RBE is not a fixed 1.1","route":"/key-papers/paper-paganetti-proton-rbe-ijrobp-2014/"}],"roadmap":[{"id":"radiation-roadmap","kind":"roadmap","name":"Radiotherapy roadmap: X-rays → shaped beams → fewer fractions, particles and FLASH","route":"/roadmaps/radiation-roadmap/"}],"trial":[{"id":"partiqol","kind":"trial","name":"PARTIQoL","route":"/trials/partiqol/"},{"id":"radcomp","kind":"trial","name":"RADCOMP","route":"/trials/radcomp/"}]}}