Development of 132 Ir sources for brachytherapy.

Abstract

Techniques for the production of three kinds of 192Ir sources, i.e. hairpin, single-pin and seed, for brachytherapy were developed in Japan Atomic Energy Research Institute. Platinumiridium, alloy wire sheathed with platinum tube in advance were irradiated by the JRR-2 or JRR-3 reactor. The platinum tube cuts off beta-rays so as to minimize unnecessary radiation exposure to patients. Irradiation conditions were determined to obtain the radioactivity of 0.74 GBq (20 mCi) for a hairpin, 0.37 GBq (10 mCi) for a single-pin and 0.37 X 10(-1) GBq (1 mCi) for a seed, respectively, at the end of irradiation. Fluctuation in the linear distribution of the radioactivity along the hairpin source or the single-pin source was small enough on the viewpoint of its application. No significant impurity or surface contamination was observed in the source produced with pre-encapsulation. Seed targets were loaded in a polyethylene tube so as to be suitable for the new treatment technique of tumor. Irradiation of seed targets, packed alternately with nylon spacers in a polyethylene tube, was found to be satisfactory for preparing ribbon sources.