Radiation therapy: Brachytherapy

Brachytherapy is an important modality in the curative management of cancers in a numerous sites of the body, which based on a precise placement of small radioactive encapsulated sources within or closed to the target volume. The absorbed dose fall-off with increasing distance from the implantation sources. High doses deliver safety to localized target region over short time, while sparing the surrounding normal tissues. Brachytherapy can be provided using low dose rate (LDR) or high dose rate (HDR) techniques. Calibration of brachytherapy source is the evaluation of the source strength where expressed in one of the internationally recommended quantities: either reference air kerma rate or air kerma strength. AAPM TG 43 had been suggested to calculate the dose around brachytherapy sources; to increase the accuracy of dose calculation it is required to use of a computational tool known as Monte Carlo method, which is samples from known possibility distributions to determine the typical behavior of a system.