Microsoft Word - RadBio_Programme_ParisSept2017

LET and RBE Conclusions 3

RBE is the ratio of dose of a “standard” radiation to dose of

the radiation of interest producing the same biological effect

The “standard” radiation is either

orthovoltage X rays (~250 kVp) or

Co gamma rays

RBE increases with LET up to a maximum at ~100 keVµm

-1

and thereafter decreases due to the “overkill” effect