Convert the following: 1 Gy equals how many rad, and 1 Sv equals how many rem?

• A. 1 Gy = 1 rad; 1 Sv = 1 rem.
• B. 1 Gy = 100 rad; 1 Sv = 100 rem.
• C. 1 Gy = 1000 rad; 1 Sv = 1000 rem.
• D. 1 Gy = 10 rad; 1 Sv = 10 rem.

Answer: (B)

Absorbed dose and dose-equivalent use different unit pairs, tied by simple scaling factors. The gray is the SI unit for absorbed dose, defined as 1 joule of energy deposited per kilogram of tissue. The rad is the older unit for absorbed dose and equals 0.01 gray, so 1 gray is 100 rad. For dose-equivalent, the rem is the older unit and the sievert is the SI unit; 1 rem equals 0.01 sievert, so 1 sievert equals 100 rem. Therefore, 1 Gy equals 100 rad, and 1 Sv equals 100 rem.