Effect of anisotropy corrections on the dynamic dose calculations in high dose rate (HDR) brachytherapy.

An analytic formalism utilizing a convolution technique is presented for the incorporation of anisotropy corrections into the dynamic (or transit) dose calculations in high dose rate (HDR) brachytherapy. A simple numerical implementation of the suggested formalism is also presented. Two calculational examples are provided in order to show some effects of anisotropy corrections on the dynamic dose calculations. Based on the results from these examples and published literature, the absence of anisotropy corrections in the dynamic dose calculations could result in a dosimetric error up to the order of 0.1 Gy during the full course of HDR brachytherapy treatments depending on fractionation and geometrical arrangement. Therefore, the incorporation of anisotropy corrections into dynamic dose calculations could eliminate this kind of error in HDR brachytherapy.