What is the term for energy absorbed per unit mass by ionizing radiation, expressed in rad or gray?

• A. Absorbed Dose
• B. Absorption
• C. ALARA
• D. Attenuation

Answer: (A)

The key idea is energy deposited in tissue per unit mass from ionizing radiation. This quantity is called Absorbed Dose. It measures how much energy the tissue actually absorbs, and it uses mass in the denominator, so the units are rad (older CGS unit) or gray (SI), with 1 gray equaling 100 rad. In dental radiology, absorbed dose tells you the potential biological impact of the X-ray exposure on the tissue.

Why the others don’t fit: absorption by itself is a general process of energy uptake and isn’t expressed per unit mass as a dose. ALARA is the principle to keep exposures as low as reasonably achievable, not a measurement. Attenuation describes how beam intensity decreases as it travels through matter, not the energy absorbed per mass.