[Dosimetric study of the applications of intracavitary radiotherapy using a remote-loading device with mobile sources].

This paper deals with the dosimetric aspects of remote-controlled afterloading irradiation devices used in brachytherapy. An afterloading device (Gammamed III) is available at Varese Regional Hospital, for intracavitary radiation therapy (low-dose rate). In the Gammamed afterloading method the radioactive sources contained in an applicator are introduced into the patient's body. This device is based on the principle of stepwise movement of three 137Cs radioactive sources (1.48; 2.96; 1.48 GBq). The results are here presented of a dosimetric study on the correspondence between algorithm for calculating isodose distributions in intracavitary treatment and experimental measurements in a phantom. Doses around the moving source were measured using thermoluminescent LiF-100 dosimeters (1 x 1 x 6 mm). Measurements were taken in a polystyrene phantom. Isodose distributions were estimated by reading the optical density of radiographic films. Doses were found to range around the calculated values within +/- 4% (with thermoluminescent dosimeters) and within +/- 8% (with films). The close agreement between the experimental and the calculated doses confirmed the acceptability of the dose distribution calculation model for the moving sources, and the Gammamed reliability.