American Society of Radiologic Technologist (ASRT) Practice Exam

For a given dose of radiation, which type yields the highest equivalent dose?

1. Alpha particles

2. Beta particles

3. X-ray photons

4. All have the same equivalent dose

The correct answer is: Alpha particles

The equivalent dose of radiation is a measure that accounts for the biological effects of different types of radiation, considering both the energy deposited in the tissue and the type of radiation involved. Alpha particles have a significantly greater mass and charge compared to other forms of radiation like beta particles or x-rays. This higher charge and mass result in alpha particles causing more ionization within the tissues they interact with, leading to greater biological damage. Equivalent dose is often expressed in Sieverts (Sv), which takes into account the radiation weighting factor specific to each type of radiation. The radiation weighting factor for alpha particles is higher than that for beta particles or x-ray photons due to their increased potential to cause cellular damage. Therefore, for the same dose of radiation measured in grays (Gy), alpha particles will yield a higher equivalent dose compared to the other types listed. In contrast, beta particles and x-ray photons have lower radiation weighting factors because they are less damaging on a per-unit basis than alpha particles. Hence, while all types contribute to overall radiation exposure, alpha particles lead to the highest equivalent dose for a given amount of energy delivered.