Mathematical algorithm model of absolute dose in radiotherapy

A algorithm of obtaining absolute dose at each tissue depth only by the mathematical calculation formula is reported. The based on integrating energy flux electron generated X-ray in range irradiation field, and spectrum ray secondary scattered are considered this process. In algorithm, water phantom field divided into several thin layers, electrons interaction between layer reaching point calculated. Finally, can be obtained accumulating contribution all layers. For with continuous spectrum, expected mass attenuation coefficient calculated for photon verified Monte Carlo simulation, difference simulation compensated a function about multiple scattering photons, shows fast descent then slow ascent. It found that ratio caused backscatter to surface dose, relationship among forward scatter, backward scatter primary ray, rays show trend first rising declining, peak value deviates from position layer. Three-dimensional spectra also compared other, particle direction. From perspective Compton effect, physical meanings different positions three-dimensional two particles explained. percentage similar small big it comes increase rays. applied non-uniform phantom, which accurately reflect distribution characteristics have less error.