What is the effect on relative biologic effectiveness (RBE) as linear energy transfer (LET) increases?

Relative biological effectiveness (RBE) is a measure used to compare the biological effectiveness of different types of ionizing radiation based on the energy they deposit in tissues. As linear energy transfer (LET) increases, RBE also increases. This is because higher LET radiation (such as alpha particles) deposits more energy per unit length in the tissue, leading to more significant biological damage.

Higher LET radiation has a greater probability of causing complex lesions in the DNA, which are more difficult for the cell to repair, making them more biologically damaging compared to lower LET radiation (like X-rays or gamma rays). Consequently, as LET increases, the ability of the radiation to cause biological effects also increases, resulting in a higher RBE.

This relationship is critical for understanding radiation therapy and the biological implications of different radiation types in medical and environmental contexts. In contrast, lower LET radiation results in lower biological effectiveness, as it is less likely to interact with biological material to produce harmful effects.