A simple formula for depth dose calculation for Co-60 teletherapy beam dosimetry

Knowledge of dose at all the points of interest, in the plane of tumour, is essential for treatment planning. A very simple formula for scatter dose calculation along the central axis of a Co-60 beam has been derived. This formula uses primary dose at depth d, scatter air ratio at the depth of maximum ionisation and the effective depth of the volume, irradiating the medium. The method for calculation of percentage depth dose at any point in the principal plane has been explained in detail. The simple form of the formulation will help in improving the treatment plans for treatments of lesions using Co-60 teletherapy machines.