Localization of radioactive sources by radiotherapy simulator and application to gynaecology

During a short-lasting high radioactivity gynaecological treatment the position of the sources does not change significantly. A fast and accurate technique was developed allowing for the determination of source positions. It is based on the use of a radiotherapy simulator. The simulator was declined by 20 degrees to the right, and the X-ray projection of the sources was copied with blue colour on a PVC foil firmly attached to the intensifier display. This was repeated with the simulator declined by 20 degrees to the left and with red. From the paralax shift the three dimensional position of sources was evaluated, and dose distribution was then calculated using a computer program.