The present invention relates to a data processing method for correlating the position of a radiation beam with the position of a target to be irradiated and contained in a structure underlying a repetitive motion comprising a plurality of successive motion cycles, the method comprising the following steps which are constituted to be executed by a computer:a) acquiring, at a processor of the computer, first external position data, second external position data and third external position data from a tracking system, describing the position of at least one external feature of said structure, for one or more sections of at least one first motion cycle occurring during a first period of time, for one or more sections of at least one second motion cycle occurring during a second period of time, and for one or more sections of at least one third motion cycle occurring during said second period of time, respectively；b) acquiring, at the processor of the computer, first target position data and second target position data from a first imaging device, describing the position of said target for at least one of said sections of said at least one first motion cycle, and for said sections of said at least one second motion cycle, respectively；c) determining, by the processor of the computer and based on said first external position data and said first target position data, correlation model data describing a positional correlation of said external position and said target position；d) determining, by the processor of the computer and based on said correlation model data and said second external position data, second predicted target position data describing a predicted position of said target for one or more sections of said at least one second motion cycle；e) determining, by the processor of the computer and based on said second target position data and said second predicted target position data, primary verification data describing whether the position of said target for said
