The method for the radiotherapy apparatus (10) that a kind of method of the present invention is issued for the radiation field (30) of quality assurance, include the following steps: that (I) provides ionization chamber detector as the radiation head (20) at the outlet (30) of the radiation field of reference detector (40) measurement dosage, it is traversed by (30) that the ionisation chamber (40), which has size and is located in the radiation laser beam, and the ionisation chamber has attenuation equivalent (40) to less than 1 millimeter of Al (II) provides one or more field detectors (50) Motion detector (50) is across (30) and measurement while radiation field dosage is from field detector (50) and from ionisation chamber (40) (3) dosage of the ratio is calculated from field detector (50) in dosage ionisation chamber (40). The present invention also relates to a kind of devices, for executing this method.
