Perturbation of dose distributions for air cavities in tissue by high energy electron

The perturbation of dose distribution adjacent to cavities in high energy electron has shown that the percentage of dose increase varies markedly as a function of the build-up layer, the length and thickness of the cavities, and the electron energy. The dose distribution showed that cavities similar in size to those encountered in the head and neck measured by industrial film dosimetry and corrected by ionization chambers. The most increased doses by measuring are resulted in a localized dose of upto 130% of that measured at the depth of maximum dose within a homogeneous tissue equivalent phantom. The measured values anc correction factors of dose perturbation due to air cavities showed in diagrams. (author)