On a simple method for routine check of the constancy of radiation quality of bremsstrahlung emitted by therapeutic particle accelerators

The constancy of radiation quality of therapeutically employed particle accelerators has to be checked at weekly intervals. Any change in radiation quality may have considerable therapeutic effects owing to its influence on dose distribution. It can be recommended to make measurements instead of, or in addition to, the axial reference-point measurement at 5 and 15 cm depth in the phantom, at 5 cm depth in the beam axis and at a reference-point about 1 cm within the geometric edge of the field, for checking the constancy of the radiation quality of bremsstrahlung. Only then, if routine checks carried out for the axial and the lateral reference-point dose ratios do not show any deviations greater than e.g. +/- 2%, radiation quality is deemed to have remained sufficiently constant for radiotherapeutical applications.