How is effective dose (EfD) calculated?

• A. Absorbed dose x Quality factor
• B. Gy x Wt
• C. Gy x Wr x Wt
• D. Wr x REM

Answer: (C)

Effective dose (EfD) is calculated using a formula that incorporates both the radiation weighting factor (Wr) and the tissue weighting factor (Wt). The correct answer reflects this relationship, as it indicates that the absorbed dose in gray (Gy) is multiplied by both the radiation weighting factor and the tissue weighting factor.

To understand this further, the absorbed dose represents the amount of energy deposited by ionizing radiation in a given mass of tissue. However, not all types of radiation have the same biological effect. Therefore, the radiation weighting factor adjusts for the type of radiation by accounting for its quality and its potential for biological harm.

The tissue weighting factor allows for consideration of the specific sensitivity of different tissues and organs to radiation exposure. By applying both the radiation weighting factor and the tissue weighting factor to the absorbed dose, the effective dose provides a more accurate representation of the overall risk of cancer and other biological effects resulting from radiation exposure across different tissues.

Therefore, the calculation of effective dose is a crucial aspect of radiological protection and risk assessment, ensuring that the medical community can make informed decisions regarding patient safety during diagnostic imaging and therapeutic procedures.