[Fifty-year-old history of cobalt radiotherapy in Hungary].

: The first patient in Hungary was treated by cobalt therapy fifty years ago at the National Institute of Oncology with a Gravicert type equipment. On the occasion of this anniversary, the 50-year history of the Hungarian cobalt therapy is reviewed, and its present role is discussed. The first cobalt unit (Gravicert) was designed by Laszlo Bozoky seven years after the first cobalt unit installation in the world in Canada. The megavoltage energy of the Co-60 source (average: 1.25 MeV) resulted in more successful treatments of deep-seated tumors compared to the X-ray therapy. In the next two-three decades, until the widespread use of the high-energy linear accelerators, the Co-60 teletherapy meant the modern radiation treatment throughout the world. Improvements of quality in radiation techniques necessitated exact localization of the tumors and developments of treatment planning methods. At the beginning, the localization was performed with X-ray machines, while the treatment planning was done manually. In 1965 a Rotacert type cobalt unit was installed at our institute. This machine was already capable of making irradiation in multiple directions and it worked in rotating mode, too. In Hungary, more cobalt units - first the Gravicert type, then foreign made machines - were gradually installed in other radiotherapy centers too. The quality of treatments was significantly improved by the introduction of the computerized treatment planning, and the foundation of the IAEA-supported National Treatment Planning Network in 1978 was an important step in this process. The next important development was the commencement of the CT image based treatment planning in 1981. With the spread of modern linear accelerators the role of the cobalt units has greatly decreased by now, however, nearly 2,500 cobalt units are still in use worldwide. Their usage could be further increased with technical developments. At present, radiation treatments are performed with cobalt units in eight out of twelve radiotherapy centers in Hungary.