Formulae for contour and inhomogeneity correction

Standard data for treatment of the patient are usually obtained in a large homogeneous phantom having a flat surface, and the radiation beam is made to be incident normally on it. The actual patient is neither homogeneous nor has a flat surface. This paper derives suitable expressions--using the total dose formula of Tripathi and Kelkar--for correcting the obliquity of the body surfaces and inhomogeneities such as bone, lung, etc. inside the body. The results obtained thus compare very well with the experimentally measured data. These equations are very simple and can readily be used with standard data to yield corrected dose distributions.