5 years of operation experience with a 4 MeV linear accelerator in radiotherapy.

The results of our experience in operating a 4 MeV linear accelerator Clinac 4 from Varian in radiotherapy are reported, especially considering the 12-hours-per-day operation for more than the last 3 years. Frequency of defects of different parts is discussed. The downtime adds up to 6 days per year, service and repair costs amount of US $ 33,--per patient.