An x-ray system comprising: at least one x-ray tube assembly a collimator forming an aperture an image detector a monitor configured to display detected images means for determining the location of at least one Region of Interest (ROI) of a patient on said displayed image a first controller connected with said means for determining the location of said at least one ROI an image processing unit connected with said image detector, said monitor and said first controller, said image processing unit configured to modify the detected image for display on said monitor according to the image parts in said at least one ROI each x-ray tube assembly comprising a plurality of cathodes and at least one anode a second controller connected with said first controller and with said at least one x-ray tube assembly, said second controller configured to control operating parameters of each one of said at least one x-ray tube assembly, said parameters comprising at least one collision location of electrons emitted from said plurality of cathodes on said at least one anode in reference to said collimator aperture and means for controlling the directions of emitted x-ray beams.
