Gynaecological treatments using the Selectron remote afterloading system.

The Manchester method of gynaecological treatment using radium 226, ovoids and a flexible intrauterine tube has been used in many centres. In Newcastle, the Manchester technique was used until 1971, when a manually afterloaded system (MAS) using caesium 137 and two source trains was introduced. In 1985, the MAS was replaced by the Selectron remote afterloading system (RAS), which also uses caesium-137 sources. The dosimetry of this remote system has been designed to produce the same shape of isodose distributions as the MAS, but shorter treatment times. The applicator design and the dosimetry of the system used in Newcastle are discussed. Dose rates achieved by the RAS are more than double those currently produced by the MAS, and a reduction in prescribed dose of 10-20% is being made. The percentage of ward staff receiving monthly doses of more than 0.2 mSv has fallen from 78% to 18% since the introduction of the remote afterloading system. The almost-cylindrical isodose distributions facilitate matching of external beam treatments using a central lead wedge to the intracavitary treatments, and work is in progress to develop this technique.