Which unit is used to express the dose in terms of estimated biological effect?

Which unit is used to express the dose in terms of estimated biological effect?

• A. Rem
• B. Sievert
• C. Rad
• D. Curie

Answer: (A)

Dose equivalent is the quantity that expresses dose in terms of the estimated biological effect of radiation. The rem was developed to capture that idea by multiplying the absorbed dose by a radiation quality factor that accounts for how different types of radiation affect tissue. So, the rem directly ties the amount of radiation to potential harm, not just energy deposited. In modern practice, the SI unit for this same concept is the sievert, with 1 sievert equaling 100 rem. The other units measure different things: the rad is an absorbed-dose unit that doesn’t account for radiation quality; the curie is a measure of radioactive decay rate (activity); exposure measured in roentgen also reflects ionization in air rather than biological effect in tissue. So rem is the traditional unit used to express dose with biological effect in mind, though sievert serves as the current standard.

Dose equivalent is the quantity that expresses dose in terms of the estimated biological effect of radiation. The rem was developed to capture that idea by multiplying the absorbed dose by a radiation quality factor that accounts for how different types of radiation affect tissue. So, the rem directly ties the amount of radiation to potential harm, not just energy deposited.

In modern practice, the SI unit for this same concept is the sievert, with 1 sievert equaling 100 rem. The other units measure different things: the rad is an absorbed-dose unit that doesn’t account for radiation quality; the curie is a measure of radioactive decay rate (activity); exposure measured in roentgen also reflects ionization in air rather than biological effect in tissue.

So rem is the traditional unit used to express dose with biological effect in mind, though sievert serves as the current standard.