As the linear energy transfer (LET) increases, what happens to the relative biological effectiveness (RBE)?

As the linear energy transfer (LET) increases, what happens to the relative biological effectiveness (RBE)?

• A. Increase
• B. Decrease
• C. Remain the same
• D. Unpredictable

Answer: (A)

As LET increases, the energy deposited along the particle’s path becomes more concentrated, producing denser ionization and more complex, clustered DNA damage that is harder for cells to repair. Because RBE compares the biological effect of a given dose to that produced by a reference radiation (like X-rays), this increased damage per unit dose makes the test radiation appear more effective. So, in general, RBE rises with LET. Keep in mind there’s a peak at intermediate LET values, and at very high LET the damage can become so localized that additional energy doesn’t translate to proportionally more biological effect, causing RBE to level off or fall. Overall, the trend supports an increasing RBE with increasing LET.

As LET increases, the energy deposited along the particle’s path becomes more concentrated, producing denser ionization and more complex, clustered DNA damage that is harder for cells to repair. Because RBE compares the biological effect of a given dose to that produced by a reference radiation (like X-rays), this increased damage per unit dose makes the test radiation appear more effective. So, in general, RBE rises with LET. Keep in mind there’s a peak at intermediate LET values, and at very high LET the damage can become so localized that additional energy doesn’t translate to proportionally more biological effect, causing RBE to level off or fall. Overall, the trend supports an increasing RBE with increasing LET.