Basic Clinical Radiobiology 2017

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 60 Co gamma rays ! RBE increases with LET up to a maximum at ~100 keVµm -1 , and thereafter decreases due to the “overkill” effect