Which statement best describes the purpose of the effective dose?

• A. It represents energy deposited in a single tissue
• B. It is the same as absorbed dose
• C. It reflects overall risk by combining absorbed dose with tissue weighting and radiation type
• D. It is measured in Gray

Answer: (C)

Effective dose is a risk-weighted measure of radiation exposure. It combines the actual energy deposited in each tissue (absorbed dose) with how sensitive each tissue is to radiation (tissue weighting factors) and with the type of radiation (radiation quality factors). By summing these weighted contributions, it provides a single value that reflects the overall potential health risk from the exposure. Because of these factors, the effective dose is expressed in sieverts, not gray, and it is not simply the energy deposited in one tissue or an exact match to the absorbed dose in a specific tissue. This means a small dose to a highly sensitive tissue can contribute more to the effective dose than a larger dose to a less sensitive tissue, highlighting the goal of comparing overall risk across different exposure scenarios.