Radiobiology > Biologic Interactions > Cel Survival Curve > Relative Biologic Effectiveness


Relationship of Linear Energy Transfer (LET) and Relative Biologic Effectiveness (RBE).

Interestingly, after a given point, higher LET results in decreased relative effectiveness. Such behavior reflects the decreased efficiency of higher LET radiation damage.

The key mechanism of biologic damage, double strand DNA breakage, is maximal at a LET of 100 keV/um Examples of 100 keV/um radiation include 300 KeV neutrons, low energy protons, and low energy alpha particles. 

For this average LET, spacing of ionizing events equals the diameter of a DNA double helix. Greater LET energies may have closer spacing of ionizations, but such additional path ionizations do not yield additional double strand breaks.

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