A system for assisting in performing an interventional procedure includes a first subsystem (1) and a second subsystem at different places, especially in different rooms. At a first place the first subsystem a) generates a first image of a subject (22) while an interventional device (12) is introduced into the subject and b) determines the position of the interventional device within the subject. At a second place the second subsystem a) generates a second image of the subject with the introduced interventional device and b) plans and/or monitors a treatment based on the second image and the already determined position of the interventional device, i.e. the second subsystem does not need to start a completely new position determination procedure, thereby reducing technical efforts. Moreover, the first and second images are generated by different imaging modalities which allows for, for instance, improved image guidance, planning and/or monitoring.