Which best describes radiation exposure?

• A. Quantity of radiation directed at the patient
• B. Quantity of radiation absorbed in the patient
• C. Quantity of radiation passing through the patient
• D. Quantity of radiation energy absorbed in air

Answer: (A)

Exposure refers to the amount of X-ray radiation directed at the patient—the beam quantity that is entering and potentially interacting with the patient’s tissues. It reflects how much radiation is available to cause ionization in the patient’s area and is closely related to the potential dose the patient could receive, but it is not the energy actually deposited in tissue. The energy deposited in tissue is the absorbed dose, which is a different measure. The portion of the beam that passes through the patient without interaction is the transmitted radiation, and exposure in air (ionization produced in air by the beam) is a different quantity used to describe how the beam interacts with air, not with the patient.