Calculation of the primary dose in the absence of electronic equilibrium

In a multilayered media at points close to the boundary of any two layers of different electronic densities, the absorbed dose due to primary radiation, can be estimated by means of secondary electrons. Assuming monoenergetic megavoltage photons incident on a two layered media, the Compton effect is a predominant mode of interaction, the primary dose is due to the electrons set into motion from the first interaction. The dose is divided into components from the upper and lower layers. The beam width must be large enough so that all electrons scattered at some angle could pass through detector point. General expression for the dose is a product of the initial photon flux at some depth, the Klein-Nisha cross section, and the ionizational mass stopping power integrated over azimuthal angle. The factor taking into account real geometry is out of the sign of integral. The latter depends only on the distance between the interface and detector for the given consequence of layers. At the interface there is a peak or drop of the dose determined by the ratio of the stopping powers under the sign of the integral. At points beyond the interface the dose decreases or increases up to electronic equilibrium region where the absorbed dose and the kerma are parallel to each other. The peak width at the base is determined by the free range of the electron with the maximum possible energy after the Compton scattering