Patent ID: 8916838

Claim:
A method for irradiating with a particle beam ( 50 ) a plurality of spots in a layer ( 65 ) of a target ( 60 ), said method comprising the steps of: providing a particle therapy system ( 10 ) for irradiating the plurality of spots with the particle beam, said system being only able to irradiate a spot with a spot dose which is larger than or equal to a minimum spot dose (Dmin), scanning the particle beam over the layer a prescribed number of layer scanning times (Nlayer_painting), irradiating selected spots of said layer in the course of each said layer scanning time with partial spot doses (Dspot_partial), characterized in that, for each spot of the layer ( 65 ), the partial spot doses (Dspot_partial) and a number of times that said spot is to be selected for irradiation (Nspot_painting), are set by a), b) and c): a) making each of the partial spot doses (Dspot_partial) larger or equal to Dmin, b) making the sum of all partial spot doses (Dspot_partial) equal to a prescribed total spot dose (Dspot), and c) making Nspot_painting=Nlayer_painting if Nspot/Nlayer_painting>=Dmin, else making Nspot_painting<Nlayer painting.