{"entity":{"id":"bragg-peak","kind":"term","name":"Bragg peak","aka":["Bragg peak","spread-out Bragg peak","SOBP","distal edge","no exit dose"],"tldr":"The spot where a proton or carbon-ion beam dumps most of its energy and then stops, so tissue behind the tumour gets almost no dose.","summary":"A charged particle slows as it travels through tissue and deposits most of its energy in a narrow peak just before it stops. That Bragg peak is why protons and carbon ions have no exit dose compared with X-rays. The spread-out Bragg peak stacks several energies to cover a tumour's depth. Linear energy transfer, and therefore relative biological effectiveness, is highest at the distal edge of the peak, which is why a constant proton RBE of 1.1 can understate dose just beyond the target. Range uncertainty of a few millimetres is the planning counterpart of that edge.","asOf":"2026-09-17","wikipedia":"https://en.wikipedia.org/wiki/Bragg_peak","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Bragg_peak"}],"tags":["radiation-wave5"],"related":[],"cancers":[],"sections":["radiation"],"technologies":["proton-therapy","carbon-ion","intensity-modulated-proton-therapy","proton-arc-therapy"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["linear-energy-transfer","relative-biological-effectiveness"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"Treatment jargon"},"route":"/terms/bragg-peak/","neighbours":{"section":[{"id":"radiation","kind":"section","name":"Radiation Therapy","route":"/fronts/radiation/"}],"technology":[{"id":"carbon-ion","kind":"technology","name":"Carbon-ion therapy","route":"/technologies/carbon-ion/"},{"id":"intensity-modulated-proton-therapy","kind":"technology","name":"Pencil-beam scanning and intensity-modulated proton therapy","route":"/technologies/intensity-modulated-proton-therapy/"},{"id":"proton-arc-therapy","kind":"technology","name":"Proton arc therapy","route":"/technologies/proton-arc-therapy/"},{"id":"proton-therapy","kind":"technology","name":"Proton therapy","route":"/technologies/proton-therapy/"}],"term":[{"id":"linear-energy-transfer","kind":"term","name":"Linear energy transfer (LET)","route":"/terms/linear-energy-transfer/"},{"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-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/"}],"trial":[{"id":"partiqol","kind":"trial","name":"PARTIQoL","route":"/trials/partiqol/"},{"id":"radcomp","kind":"trial","name":"RADCOMP","route":"/trials/radcomp/"}]}}