A method for EPID-based verification, correction and minimization of the isocenter of a radiotherapy device includes the following: Positioning a measurement body； applying an irradiation field； capturing a common dose image of the measurement body； creating a dose profile on the basis of the captured dose image； determining an inflection point in a plot of the dose profile； linking positions of the inflection points to bodily limits of the measurement body； determining position of a center point of the measurement body relative to an EPID-center； determining a differential vector from a deviation in position of the center point of the measurement body from the EPID-center and from a deviation in position of the field center point of the irradiation field from the EPID-center； and correcting the current radiological isocenter.
