Tissue Air Ratio
Also written as: TAR — Tissue Air Ratio
Dosimetric parameter comparing radiation dose in tissue at depth to dose in air at the same point, used in dose calculation algorithms.
Full Definition
Tissue Air Ratio (TAR) is a fundamental dosimetric quantity that compares the absorbed dose at a specific depth in tissue to the absorbed dose that would be measured in air at the same geometric point. TAR values are independent of source-to-surface distance and are primarily used in dose calculation algorithms for irregular field shapes and missing tissue calculations. This parameter accounts for beam attenuation and scattered radiation contributions, making it essential for accurate dose computations in heterogeneous patient geometries and treatment planning systems.
Usage
Usage note: Commonly abbreviated as TAR; distinguish from TMR (Tissue Maximum Ratio).
In Context
- "Tissue air ratio measurements were performed during beam commissioning for multiple field sizes." — Commissioning documentation
- "The dose calculation algorithm incorporated TAR data for irregular field shape corrections." — Physics validation report