Method of reducing the x-ray dose in an x-ray system

A method of obtaining medical images of a patient using a cone beam computed tomography scanner, the method comprising:

• defining a region of interest of the patient;
• obtaining at least two tracking images of a tracking element taken with at least one camera having a known positional relationship relative to a radiation source and/or sensor;
• determining any movement of the tracking element between the acquisition of at least two tracking images;
• obtaining a plurality of x-ray images of the region of interest simultaneously with the tracking images;
• and
• dynamically adjusting a collimator of the radiation source of the cone beam computed tomography scanner to compensate for any movement of the tracking element between the acquisition of the at least two tracking images, providing that the field of exposure of the x-ray radiation is confined to the region of interest.