A method for irradiation treatment planning for a target volume to be irradiated includes specifying a plurality of data sets. The target volume to be irradiated is depicted in each data set of the plurality of data sets. The data sets differ in that the target volume has another position and/or shape. A data set is selected from the plurality of the data sets and other data sets are registered to the selected data set. The method includes forming an amalgamation of the depicted target volumes using the registrations of the other data sets to the selected data set, and determining an area at risk in the selected data set. The method includes modifying the amalgamation of the target volumes such that the area at risk is excluded from the amalgamation of the depicted target volumes. An irradiation treatment plan is calculated using the modified amalgamation of the target volumes.
