The roentgen is the unit of

The roentgen is the unit of

• A. The unit that expressed x-ray or gamma radiation exposure
• B. The unit of absorbed dose
• C. The unit of dose equivalent
• D. The unit of activity

Answer: (A)

Exposure is what the roentgen measures: the ionization produced in air by X-ray or gamma radiation. This makes it the unit of exposure. It is not a measure of energy deposited in matter (that’s absorbed dose, measured in rad or Gy), nor of biological effect (dose equivalent, in rem or Sv), nor of how radioactive a source is (activity, in curie or Bq). In soft tissue, about 1 R roughly corresponds to 0.01 Gy, illustrating the relationship between exposure and dose while keeping them as distinct quantities. The roentgen is largely historical; modern practice uses coulombs per kilogram for exposure and gray for absorbed dose.

Exposure is what the roentgen measures: the ionization produced in air by X-ray or gamma radiation. This makes it the unit of exposure. It is not a measure of energy deposited in matter (that’s absorbed dose, measured in rad or Gy), nor of biological effect (dose equivalent, in rem or Sv), nor of how radioactive a source is (activity, in curie or Bq). In soft tissue, about 1 R roughly corresponds to 0.01 Gy, illustrating the relationship between exposure and dose while keeping them as distinct quantities. The roentgen is largely historical; modern practice uses coulombs per kilogram for exposure and gray for absorbed dose.