Which expression correctly represents the effective dose?

• A. E = D × w_R
• B. Σ w_R H_T
• C. Σ w_T H_T
• D. H_T / w_T

Answer: (C)

Effective dose represents the overall risk by accounting for how sensitive each tissue is to radiation. To capture this, you take the equivalent dose to each tissue, H_T, and weight it by that tissue’s weighting factor, w_T. Then you add (sum) these contributions across all tissues. This gives E = Σ_T w_T H_T. Since H_T already includes the effect of radiation type via w_R (H_T = D_T × w_R), this formulation properly combines both tissue sensitivity and radiation type into a single dose that reflects total stochastic risk.

The other expressions don’t line up with how effective dose is defined. They either try to combine factors without summing across tissues, misuse the radiation weighting factor, or cancel out the tissue weighting inappropriately.