to both sides in order to position a patient situated on the patient support 5 the patient support 5 may be positioned in all three spatial coordinates with respect to the support frame 3 and to the transducer 4 the x ray location device 2 is designed as a commercially available x ray c arc the actual c arc 8 is part of the support frame an x ray source 9 is arranged at one end of this arc 8 an x ray image amplifier 10 is arranged at the opposite side the c arc 8 is designed as a profile and is guided in the direction of its arc on an arm 11 which is in turn connected to the undercarriage 13 by means of a stroke device 12 not shown in detail the arm 11 is mounted on the stroke device 12 so that the entire c arc can be pivoted with the arm 11 about the axis 40 which need not necessarily coincide exactly with the axis 7 to connect the x ray location device 2 to the treatment apparatus 1 the c arc 8 is first of all aligned by means of the stroke device 12 so that the axis 40 is approximately flush with the axis 7 the c arc is then pushed into the support frame 3 of the treatment apparatus 1 at its lower end supporting the x ray source 9 until the x ray source 9 is aligned with the x ray window not shown provided in the transducer 4 the coupling shown in detail using fig2 to 4.