[Accuracy of the dose distribution]

The purpose of physical treatment planning is to deliver the absorbed dose to the target volume within +/- 5% of the prescribed dose. The greatest accuracy is required for the target volume adjacent to the critical tissues. Accuracy of the dose distribution in the patient is affected by the calculation errors of the dose and the set-up errors of the patient for daily treatments. In order to reduce the errors, quality assurance programme shall be carried out. Quality assurance programmes include acceptance tests and periodic performance tests of the dosimeter, the treatment unit and accessories. The importance of the calibration system of ionization chamber, computerized set-up system and quality assurance programmes is emphasized.