The unit used to measure absorbed radiation dose is the Gray (Gy). It quantifies the amount of energy deposited by ionizing radiation per unit mass of tissue, where 1 Gray equals 1 joule per kilogram. This measurement is crucial in clinical settings to assess the direct biological impact of radiation exposure on tissues. Unlike Sievert, which accounts for radiation type and biological effect (effective dose), Gray strictly measures the physical dose absorbed, making it key in radiation therapy and radiology.

Reference: Radiobiology for the Radiologist, Eric J. Hall, 7th Edition.