The present invention relates to a method for determining an energy fluence correction in a quality assurance system for a radiation therapy apparatus, which method comprises receiving a treatment plan description generating a set of measured phantom dose values generating a set of determined phantom dose values, by determining phantom dose values on basis of at least the treatment plan description and a phantom description determining a set of phantom dose corrections on basis of at least the set of determined phantom dose values and the set of measured phantom dose values and determining an energy fluence correction on basis of at least the set of phantom dose corrections.It further relates to a method for determining a reconstructed patient dose distribution on basis of at least the energy fluence correction, a patient description, and further data related to the treatment plan description.It also relates to corresponding quality assurance and control systems.
