What does Tissue Air Ratio (TAR) compare?

Tissue Air Ratio (TAR) is a crucial concept in radiation dosimetry, specifically in the context of therapeutic radiation. It compares the dose delivered at a certain depth in a tissue or phantom to the dose at the same depth in air. This comparison is essential because it accounts for the different interaction behaviors of radiation as it passes through media such as tissue versus air.

By establishing this ratio, health professionals can better understand how much radiation is absorbed by tissue compared to that in air, facilitating accurate dose calculations for treatment planning. This measurement is particularly important when assessing the effectiveness of radiation therapy on tumors while minimizing exposure to surrounding healthy tissues.

The other choices do not accurately reflect the definition of TAR. For instance, comparing doses at different depths in air does not consider tissue interactions, while comparing patient dose versus the general public or radiation exposure between children and adults involves epidemiological assessments rather than physical depth measurements in dosimetry.