[Possibilities of dose distribution in the afterloading technic]

Remote (controlled) afterloading installations, offer the possibility to improve the dose distributions of the different applicators, since this apparatus permits the employment of artificial radionuclides with a high specific activity and with low energy of gamma rays. It is therefore possible to incorporate effective shielding into the applicators. The possible individual fitting of the dose distribution, however, demands considerable clinical effort, as the extension of the tumor in question has to be ascertained with sufficient accuracy. Otherwise, underdosage to tumor cells may happen within the shielded area. Most afterloading techniques are using stiff applicators and geometrical fixation within patients; configuration and position of the radiation sources in the patient therefore remain unchanged during the whole irradiation. Thus, it becomes possible to adapt additional external irradiation more exactly than before to the intracavitary dose distribution.