A system (1) for positioning a patient for radiotherapy in accordance with patient specific data including a first volumetric image (e.g. a pCT image) of the patient comprising tissue label data and dose specification data is provided that comprises an imaging device (2), a positioning device (3) and an optimization controller (4). The imaging device (2) is configured to provide a second volumetric image (e.g. an rCT image) of the patient including a designated part of the patient to be treated. The positioning device (3) is provided to hold the patient in a variable position and/or orientation in the beam of radiation for an accurate intervention to a designated part of the patient. The optimization controller (4) comprises a dose based control module configured to provide registration control data (ΔP) to guide the positioning device (3) so that the actually applied treatment dose optimally matches the planned treatment dose
