Procedure for field axes measurement, beam indication adjustment, and figure of convergence determination within performance tests for radiation therapy equipment.

A routine measuring procedure for the verification of radiation field axes and figure of convergence within a spatial resolution of +/- 0.5 mm is described. Measurements are done in two parallel planes in a certain distance before and behind the presumed isocentre. The used test arrangement permits rapid check and controlled adjustment of the alignment of beam or isocentre indicating devices for all isocentic radiation therapy equipment.