Linear Energy Transfer (LET)
A measure of the rate at which an ionizing radiation particle deposits ionization energy along its path length through biological tissue.
Governing formula
LET = dE / dx
SI unit
keV/μm (Kiloelectronvolts per micrometer)
In depth
Low-LET radiation (X-rays, gamma rays, electrons; LET ~0.3–3 keV/μm) causes sparse ionizations easily repaired by cells. High-LET radiation (alpha particles, heavy ions; LET ~100–200 keV/μm) produces dense clustered DNA ionization damage.
Examples in the real world
Alpha particles acting as high-LET radiation (~100 keV/μm) producing irreparable DNA double-strand breaks.