American Society of Radiologic Technologist (ASRT) Practice Exam

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Which of the following measures the amount of energy deposited by radiation in a material?

  1. Roentgen

  2. Gray

  3. Sievert

  4. Curie

The correct answer is: Gray

The Gray is the correct choice because it specifically measures the absorbed dose of radiation, quantifying the amount of energy deposited per unit mass of a material. It is defined as one joule of radiation energy absorbed by one kilogram of matter. This makes it particularly relevant in radiologic and radiation therapy contexts, where understanding the energy imparted to tissues is crucial for assessing potential biological effects and therapeutic outcomes. In contrast, the Roentgen measures exposure to ionizing radiation in air, focusing on the ionization produced rather than the energy absorbed by matter. The Sievert is a unit that takes into account the biological effect of radiation, factoring in the type of radiation and its impact on human tissue, rather than just the energy deposited. The Curie is a measure of radioactivity, indicating the rate of decay of radioactive materials, not the energy transfer to matter.