Which particle type is most likely to cause greater biological damage per unit dose due to higher LET?

Which particle type is most likely to cause greater biological damage per unit dose due to higher LET?

• A. Protons
• B. Alpha Particles
• C. Beta Particles
• D. Gamma Rays

Answer: (B)

High LET radiation deposits energy densely along its path, creating many ionizations in a small region and producing complex, clustered DNA damage that is harder for cells to repair. Alpha particles are heavy and highly charged, so they deliver a burst of energy over a very short range in tissue. That dense ionization leads to more biological harm per unit absorbed dose (higher relative biological effectiveness) than particles that spread energy more sparsely. Protons, beta particles, and gamma rays all have lower LET, meaning their energy is deposited more gradually along larger distances. This results in less immediate, local damage for the same absorbed dose compared to alpha particles, even though they can travel farther or penetrate more. So, alpha particles are most likely to cause greater biological damage per unit dose due to their high LET.

High LET radiation deposits energy densely along its path, creating many ionizations in a small region and producing complex, clustered DNA damage that is harder for cells to repair. Alpha particles are heavy and highly charged, so they deliver a burst of energy over a very short range in tissue. That dense ionization leads to more biological harm per unit absorbed dose (higher relative biological effectiveness) than particles that spread energy more sparsely.

Protons, beta particles, and gamma rays all have lower LET, meaning their energy is deposited more gradually along larger distances. This results in less immediate, local damage for the same absorbed dose compared to alpha particles, even though they can travel farther or penetrate more.

So, alpha particles are most likely to cause greater biological damage per unit dose due to their high LET.