[Plate method in gynecologic afterloading procedures. A: Physical requirements and introduction to radio-oncology]

A brachytherapy by afterloading technique which would be adequate to the method of Stockholm, Munich, or Hamburg met with difficulties until the year of 1977, because there were no practicable afterloading probes in the form of plates. As for the charge of a radium plate in which radium tubes are joined together in different arrangements according to the technique applied, the probes of multiple probe units can be arranged in a parallel order, so that the effect of a radiation shield is produced. Plates made of plexiglas or of synthetic material in which the probes with the sources are inserted by corresponding boreholes serve as carriers for the afterloading probes. The dose to the points P, A and B, R and V is calculated taking into consideration the distance between the probe plate and the target volume, and the dose distribution is optimized by means of CT and of an irradiation computer. The irradiation of large tumor volumes can now be performed under the same conditions as for radium therapy. In our Department, the high dose-rate method is applied for this irradiation for colpostatic reasons. Between October 1, 1976 and December 31, 1983, 1272 patients were submitted to this treatment. A plate applicator which has satisfied all requirements was developed in 1981 in collaboration with the companies Buchler, Braunschweig and Chemomedica, Vienna.