To provide a method to direct a surgical means, for which an X-ray linear accelerator is used, to the target region of a patient.

A stated device selectively irradiates the target (18) in the patient (14). The three-dimensional image of an imaging region (16) around the target is provided. A beam device (20) emits a collimating beam. Beams (26 and 28) for the diagnosis pass the imaging region at angles which are already known to each other and not zero. Thus, the image of a projected shadow in the imaging region is obtained. The electronic display of the image is compared to reference data in which the target (18) is arranged. The focal point of the collimating beam is adjusted onto the target region, and relative locations of the beam device and the physiological body are regulated. The comparison is repeated with a short period of time interval, and the regulation is repeated with the focal point of the collimating beam adjusted to the target region (16) when required.