What is the SI unit for measuring radiation absorbed dose?

The SI unit for measuring radiation absorbed dose is the Gray (Gy). The Gray quantifies the amount of radiation energy absorbed per kilogram of matter, specifically tissue. It is defined as one joule of radiation energy absorbed per kilogram of matter. This unit is essential in radiology and radiation therapy because it helps to assess the biological effect of radiation on human tissue, guiding safety standards and treatment dosages.

The Rad, while historically used in the United States, has been largely replaced by the Gray in scientific and international contexts. The conversion is straightforward: 1 Gray is equivalent to 100 Rads.

Roentgen measures ionization in air and is used primarily for X-rays and gamma rays, but it does not directly measure the absorbed dose in tissue.

The Sievert (Sv) is a unit that measures the effect of radiation on the body, considering the biological impact, but it is not directly used to express absorbed dose in the same way that Gray does. The Sievert incorporates the absorbed dose along with a quality factor to account for the biological effectiveness of the radiation type.

In summary, the Gray is the correct choice as it specifically indicates the radiation absorbed dose, a critical concept in radiation safety and therapy.