Which unit is used to measure the quantity of radiation received by a patient?

The gray (and its predecessor, the rad) is the unit used to measure the absorbed dose of radiation received by a patient. This means it quantifies the amount of energy deposited by ionizing radiation in a given mass of tissue, which is critical when assessing the potential biological effects on the human body.

Using the gray or rad allows healthcare professionals to evaluate the level of radiation exposure in terms of its potential harm or therapeutic effect, particularly in contexts such as radiation therapy for cancer treatment. The gray is defined as the absorption of one joule of radiation energy by one kilogram of matter.

Other units mentioned serve different purposes in radiology. The rem and roentgen are related to dose equivalent and exposure, respectively, while the curie measures radioactivity rather than dose, making those units less relevant for evaluating the quantity of radiation received by a patient.