an x - ray c - arm system 10 is arranged in a treatment room , of which only the x - ray c - arm 10 with x - ray source 12 and x - ray flat panel detector 14 is shown by way of representation in the figure . the movements of the x - ray c - arm are controlled by a control facility 16 . the control facility 16 receives input signals by way of an input facility 18 . by way of example , a joystick is shown for the input facility , the inputs can take place in a manner known also by way of pushbuttons , a computer mouse or a keyboard . useful displays are shown on a monitor 20 for an operator . a patient couch , upon which a patient rests during the operation , conventionally forms part of the x - ray c - arm . for reasons of clarity , the patient couch and patient are omitted in the figure . a plurality of video cameras 22 is now arranged in the space in which the x - ray c - arm system is positioned . three such video cameras 22 are shown in the figure , the inventive system then operates particularly expediently if eight cameras are arranged in the space . the video cameras 22 are set up ( or at least can be set up ) such that they are able to capture surroundings of the x - ray c - arm 10 with the same . the images of the video cameras 22 are evaluated . the video cameras 22 are connected to the control facility 16 in the figure , the image evaluation can however take place in a special facility . the result of the analysis must however in the latter case be made available to the control system actuating the x - ray c - arm , so that it is ultimately possible to recombine the systems to be evaluated to form a single control facility . the illustrated coupling of the video cameras 22 to the control facility 16 therefore represents the most natural instance . the number of video cameras 22 and their alignment is now selected such that a three - dimensional item of information relating to the occupation of the space can be captured . a statement can be made on the basis of the images of several video cameras 22 at one volume element 22 as to whether this is occupied by an object or is completely object - free , i . e . is exclusively filled with air . in the figure , the volume element 24 is free of objects . other volume elements , namely volume elements 26 , 26 ′ are however occupied by a person 28 . the control facility 16 now detects on the basis of the images recorded by the video cameras 22 for all volume elements , for which this is possible , whether or not these are occupied by an object according to the type of person 28 . within the scope of the treatment of the patient ( not shown in the figure ), it now results that the x - ray c - arm 10 has to be moved , e . g . has to be pivoted in accordance with arrow 30 . the x - ray c - arm 10 with the x - ray tube 12 and x - ray flat panel detector 14 naturally passes through volume elements 32 during its pivoting movement , which were previously not captured by the x - ray c - arm 10 . the whole space 23 passed through by the flat panel detector 14 and the part of the x - ray c - arm 10 associated herewith during the movement according to arrow 30 is marked in the figure with a dotted line . the control facility 16 has a cad ( computer aided design ) model of the x - ray c - arm , in particular also of the flat panel detector 14 . a space model is used in the control facility 16 . the control facility 16 now determines which volume elements 32 , like for instance volume element 32 , are passed through during the movement of the x - ray c - arn , which is desired ( target movement ). this quantity of volume elements is now subsequently examined so as to determine whether it belongs to volume elements 24 , which are free of objects or whether it belongs to volume elements 26 and / or 26 ′, which are occupied by an object . the figure shows that the volume element 26 ′ belongs to the intersection of the volume elements , which are at the same time occupied by an object 28 , and were passed through during the target movement of the x - ray x - arm according to arrow 30 . a single such volume element 26 ′ is sufficicent for the control facility 16 to identify that the movement of the x - ray c - arm had been obstructed . the control facility 16 thereupon emits a warning signal on the monitor 20 to the operator and can in particular also block the movement of the x - ray c - arm 10 . if however there is no volume element according to the type of volume element 26 ′, i . e . if the entire space passed through by the x - ray c - arm 10 during its target movement is free of obstacles , the movement of the x - ray c - arm is released . if necessary , provision can be made for the previously entered target movement to be immediately implemented after the release . the control facility 16 can also implement a pattern recognition on the basis of the information relating to the volume element 26 and can thus recognize which type of object appears as an obstacle during the target movement of the x - ray x - arm 10 . it is currently possible to detect for instance that the object 28 is a person and to output on the monitor 20 “ person blocking movement of the x - ray c - arm ”. the operator can then ask the person 28 to leave the swivel range of the x - ray c - arm 10 . if the object 28 is a subject , this can be removed . for representational reasons , only the swiveling motion backwards and forwards according to arrow 30 was mentioned as the movement possibility for the x - ray c - arm . the method according to the invention is also used in more complex target movements , in particular movement sequences . it is possible to work in the n - level mode with the aid of the one x - ray c - arm , with which the x - ray c - arm 10 captures certain working positions alternately . prior to each change , the system checks whether an obstacle prevents the movement of the x - ray c - ann 10 . as a rule that no obstacle is present , it is possible to rapidly move backwards and forwards between the individual operating positions .
with an x - ray imaging system with a moveable part , obstacles can stand in the way of the movement of the moveable part . in accordance with the invention , video cameras capture the occupation of the space by objects using volume elements . it is possible to determine at a target movement of the moveable part which volume elements are passed through during this . if one of these volume elements proves to be a volume element occupied by an object , the movement of the moveable part is prevented , otherwise it is enabled or actively implemented .