A method of adjusting an irradiation treatment plan, the plan constituted of: obtaining a plurality of reference scans of a target tissue over a breathing cycle obtaining a pre-treatment scan of the target tissue identifying the reference scan whose phase is consonant with the obtained pre-treatment scan computing at least one motion vector field between the identified reference scan and another of the plurality of reference scans different from the identified reference scan applying the at least one computed motion vector field to one of the obtained pre-treatment scan and the another of the plurality of reference scans so as to obtain at least one synthetic scan whose phase is consonant with the other of the obtained pre-treatment scan and the another of the plurality of reference scans and adjusting one of an irradiation dose, irradiation angle and irradiation positioning responsive to the at least one synthetic scan.
