A novel tracking technique for the continuous precise measurement of tumour positions in conformal radiotherapy.

Changing tumour positions induced by organ motion can impede the full exploitation of the strengths of conformal radiotherapy. The unnecessary irradiation of healthy tissue surrounding the target volume can be the consequence. To overcome this, one should measure tumour positions directly and continuously with high resolution in space and time. We have developed a novel tracking technique which will allow this. The method can also be used to survey and monitor the patient positioning. The proper functioning of our method has been technically demonstrated at PSI with the help of phantom irradiation with protons. Implementation into the clinical environment is now beginning.