Science of brachytherapy is currently increasing in the field of cancer therapy. By virtue of the development of computer assisted technologies, we can reap the benefits of accurate radiotherapies more than ever, which enabled precise irradiation to a target safely avoiding unnecessary involvement of the surrounding normal tissue. Unlike teleradiotherapy provided by X-ray linear accelerator, brachytherapy utilizes radiation source placing inside or close to the target. Taking advantage of practical availability of the physical characters including decay modes, half-lives, and decay energies of the radioisotopes, various practical insertion or deployment methods have been developed. Some of these are technically sophisticated. A precise treatment planning requires accurate dose calculation algorithm.
