Isodose 2D determining in water phantom regular and irregular fileds in radiation therapy for caculation modulated dose

The dose distribution plays an importance role in the commercial treatment planning algorithm; therefore، a patient-independent model is needed to calculate the modulated profile. A general formula has been proposed to calculate the profiles for any field shape in the wedged and non-wedged، blocked and non-blocked fields under symmetry and asymmetry photon beam conditions. Percentage depth doses (PDDs) are measured for a large number of square fields for both energies، and 45º wedge. Accessing the accuracy of the model for profile prediction، several measurements were carried out for some special treatment fields. Comparison between measurements and calculation showed that using the γ-index in the range of 3% error in the low dose gradient region and a 3mm isodose shift in the penumbra region. This analytical approach provides a general fast and accurate algorithm to calculate dose distribution for any treatment field in conventional radiotherapy.