Fig. 3-12 Structure of the irradiation capsule which has been recently developed for the production of an 192Ir source.

Fig. 3-13 Cross section of the 192Ir source for the RALS system

Bronchial tube An applicator is passed through a "T" pipe which is inserted into the bronchial tube.   Bile duct Theapplicator made of thin steel wire (1.9 mm in diameter), which can be inserted directly into the cystic duct is used for its treatment.

Fig. 3-14 Some applications of the RALS system for the medical treatment of cancer

The RALS system used for the radiotherapy of cancer has rapidly spread throughout the world. The reason for this is that a 192Ir source is very small for all its high radioactivity and gives only little damage to the sound tissue neighboring the cancer, due to its gamma energy which is weaker than that of 60Co. Several tens of noted medical institutions in Japan have already introduced the RALS system, and its superiority has been established. The use of flexible super thin wire as the guide rope of the source facilitated its insertion into the cancerous part. While it was generally agreed in the past that the medical treatment of a cancer nested in an internal narrow region, the bile duct and the bronchial tube and the like, of the human body, was very difficult. The development of the 192Ir source and its applicator have made such a local remedy possible and a large increase in its applications is expected. The technical development for the production of the 192Ir source, including the neutron irradiation condition in a reactor and the source encapsulation technique, are being performed at JAERI.

Reference A. Sato et al., Production of 198Au and 192Ir Sources for Cancer Therapy, JAERI-M 91-020 (1991).

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