The Extension of the Concept of Tissue-Air Ratios (TAR) to High-Energy X-Ray Beams

Abstract

A new function, the tumor-maximum ratio (TMR), is defined for high-energy x-ray beams, permitting the concept of isocentric dose calculations to be extended into the high-energy x-ray region. The central axis dose in the medium is computed from a derived function, the attenuation factor α. The method of dose computations using α is illustrated, and TMR and a tables for 6 MeV x rays are provided. With an increasing number of isocentric high-energy x-ray generators being employed in clinical dosimetry, the application of α should be helpful in the necessary calculations.