To compute the equivalent dose (EqD), which variable must be known?

To compute the equivalent dose (EqD), which variable must be known?

• A. RBE
• B. Wr
• C. LET
• D. Wt

Answer: (B)

Equivalent dose reflects not just how much energy is deposited, but how biologically damaging the radiation type is. To get EqD, you multiply the absorbed dose by a radiation weighting factor that represents this biological effectiveness. That weighting factor is Wr, so knowing Wr is essential to compute EqD. In practice, the formula is EqD = D × Wr, where D is the absorbed dose. The weighting factor varies with radiation type (for example, alpha particles have a higher Wr than X-rays), which is why Wr is the key variable. RBE, LET, and Wt relate to other ways of characterizing risk or dose, but they aren’t the factor used in the standard EqD calculation.

Equivalent dose reflects not just how much energy is deposited, but how biologically damaging the radiation type is. To get EqD, you multiply the absorbed dose by a radiation weighting factor that represents this biological effectiveness. That weighting factor is Wr, so knowing Wr is essential to compute EqD.

In practice, the formula is EqD = D × Wr, where D is the absorbed dose. The weighting factor varies with radiation type (for example, alpha particles have a higher Wr than X-rays), which is why Wr is the key variable.

RBE, LET, and Wt relate to other ways of characterizing risk or dose, but they aren’t the factor used in the standard EqD calculation.