in the example explained below the components of the navigation device described and the steps of the method described each represent individual features of the application to be considered separately from one another , and which also develop the application independently of one another and thus are also to be regarded individually or in a combination other than the one shown as a component of the application . furthermore , the embodiments described can also be supplemented by others of the features of the application already described . fig1 shows a patient 10 who is positioned on an operating table 12 . the patient 10 is prepared for an operation in the context of brachytherapy and if possible should not change his position during the implantation of applicators for the brachytherapy . in order to monitor the position of the applicators during implantation , a navigation device 14 is provided in the operating room in which the operating table 12 is located . the navigation device 14 comprises an imaging facility 16 which is positioned so as to move in respect of the operating table 12 ; in the example in fig1 this can be an x - ray c - arm 18 or a mrt device which can rotate about the operating table 12 . the imaging facility 16 can in the first case for example comprise an x - ray source 20 and an x - ray flat - panel detector 22 , so that it can also be used during the operation as a projection unit for obtaining two - dimensional x - ray images . the imaging unit 16 can be the x - ray and dynact product from siemens ag , two x - ray sources and two detectors being used in order to reduce the recording time for the provision of an individual 3d image dataset and to enable the sight out of the two different angulations the imaging unit 16 is linked to a control unit 24 and a display unit 26 . the control facility 24 can for example comprise a personal computer or a workstation computer . the display unit 26 can for example be a monitor or another personal computer with a monitor . the link can for example be effected by a data network 28 , such as an ethernet . to treat the patient 10 by brachytherapy , a sequence of work steps is performed , which form a treatment protocol or workflow and by which the planning , performance and final evaluation are established for brachytherapy as an interventional method of radiotherapy . the sequence of work steps is illustrated in fig2 . in addition , for the explanation of the treatment protocol reference can be made to fig3 and in addition it is assumed below that in the case of the patient 10 a tumor 30 in a prostate 32 is to be destroyed by brachytherapy using radioactive irradiation . in a step s 10 the patient 10 is , according to the treatment protocol , brought into a room before the actual operation , in which a preoperative 3d image dataset ( pre - op 3d ) is obtained for example by a computed tomography system and / or a magnetic resonance tomography system . a very high soft - tissue contrast is set here , so that the physician can precisely visually delimit the individual organs ( e . g . the bladder 34 , the rectum 36 , the prostate 32 itself and where appropriate the uterus ) surrounding the tumor 30 . as these organs 32 , 34 , 36 are very sensitive to radiation , they are also included in a calculation of a radioactive radiation dose ( ds ) in brachytherapy in a step s 12 . with the help of the preoperatively obtained 3d image dataset in step s 10 the physician first hereby performs the tumor diagnosis . the resulting type , position and size of the tumor 30 can hereby be determined by the physician . based on the tumor diagnosis and the preoperatively obtained 3d image dataset the physician uses a dose planning facility , for example a personal computer with dose planning software and / or a dose planning application loaded on it , to determine a number and target positions of applicators 38 which are to be implanted into the patient 10 , in order to be able to introduce radioactive material into the tumor 30 . in addition the dose planning facility supplies a simulation for the dose distribution on the basis of the determined target positions of the applicator 38 . the dose planning facility can also comprise order management , which on the basis of the result of the dose planning ( number of applicators 38 , the strength or intensity of the individual radioactive radiation sources ( seeds ) which are to be introduced via the applicators 38 ) generates order data ( ord ) in a step s 14 which is suitable for use in a computer system of the hospital for ordering the radiation sources ( seeds ). furthermore , other necessary materials can be ordered fully automatically in the same way . if desired , provision can also be made here for the order to be placed only where there is additional confirmation by for example the physician or other hospital personnel . as soon as the radioactive material ( where appropriate after a few days ) is ready , the patient can , according to a development , be automatically booked in for the operation by the dose planning facility or else by another administration program in a step s 16 . the operating room can likewise be reserved and the personnel required for the operation can be scheduled fully automatically in a step s 16 . use can be made here of the functionalities of a hospital information system ( his ) known per se . the dose planning facility must then be fitted with a corresponding software interface . according to the operation planning the actual operation then takes place at a set time , i . e . the patient 10 is positioned on the operating table 12 , the environment is sterilized , the implantation of the applicators 38 into the tumor 30 is performed and the position of the applicators 38 in the tumor 30 is checked . the steps explained below , which can be performed in connection with the operation in the sterile environment and without repositioning the patient 10 , are summarized in the box op in fig2 . after successfully positioning ( pos ) the patient in a step s 18 an intraoperatively obtained 3d image dataset ( intra - op 3d ) is obtained in a step s 20 of a region of the body 40 of the patient 10 in which the tumor 30 is located . in the present example the pelvis 42 with the organs located therein 32 , 34 , 36 can be mapped three - dimensionally . the 3d image dataset obtained in step s 20 has a high soft - tissue contrast . depending on the imaging unit 16 used corresponding operating parameters are provided for this from the prior art . using the intraoperatively obtained 3d image dataset the physician obtains a precise statement about the current position of the organs 32 , 34 , 36 and of the tumor 30 . it can be provided that in step s 20 the 3d image dataset is obtained using an especially low radiation dose if the imaging facility 16 comprises an operating mode . to this end it can then be provided that in a step s 22 the intraoperative 3d image dataset obtained in this way can be merged ( fuse ) with preoperatively obtained 3d image data , as was obtained for example in step s 10 , on the basis of anatomical landmarks . the feature of this is that the patient 10 is exposed to a lower x - ray dose because the physician needs less scans than conventional operation . in another step s 24 the control facility 24 is used to calculate a volume model ( vol ) of the region of the body 40 . this can be formed directly from the 3d image dataset of step s 20 or from the combined 3d image dataset of step s 22 . the volume model can also contain a representation of the applicators 38 . the applicators 38 illustrated in the volume model can here comprise the target position as was set in step s 12 using the dose planning facility . the current position of the applicators 38 in the region of the body 40 can also be determined from a location facility ( not shown ) for instrument navigation , as is known per se from the prior art . in order to clarify the current position of the applicators 38 in the region of the body 40 to the physician , the volume dataset of the volume model , in other words the 3d image dataset with the additional data relating to the applicators 38 , as obtained in step s 24 , is transferred to the location facility in an embodiment of the flow trace . in a step s 26 this updates the position of the applicators 38 in the volume model at predetermined time intervals and visualizes the position on the display unit 26 for the physician . the location facility 29 here comprises markers ( mark ), located by sensors , which are attached to the applicators 38 , evaluation software which can be executed for example by the control facility 24 which evaluates said sensor signals , and software for generating the representation for the display facility 26 . by continuously updating the position data a live image of the navigation is hereby displayed to the physician on the display unit 26 . the region of the body 40 where the applicators 38 are located is displayed to the physician in the volume model . thus without any additional fluoroscopy of the patient 10 he can position all applicators 38 precisely . it can additionally be provided , in a step s 28 on the basis of the volume model , for a dose distribution ( ds dist ) of the radioactive irradiation to be determined on the basis of a simulation of the irradiation . a resultant display on the display facility 26 is represented by way of example in fig4 . the tumor 30 into which the applicators 38 are inserted is for example displayed to the physician in a sectional image . depending on the position of outlet openings for radioactive radiation and the radiation intensity of the radiation sources introduced in the simulation and the dwell time of the radiation sources in the applicators 38 a radiation distribution 44 is calculated for the individual applicators and is displayed for example in the form of a closed curve . the area delimited by the respective curve of the dose distribution 44 can e . g . show that the tumor cells will be killed in the area with a predetermined probability , for example 95 % and more , after the radioactive irradiation . so far a variant of the treatment protocol has been described which uses a location facility with markers . in another variant of the treatment protocol a conventional 2d x - ray control can also be used during the operation to check the position of the applicators 38 . the imaging facility 16 can also for example be used to this end , if it also enables 2d projection data to be created , in other words e . g . 2d x - ray data . this is possible for example with the x - ray flat - panel detector 22 described . an optimal c - arm position and orientation ( x , y , z position , lao , rao , cranial / caudal ) of the projection facility for monitoring the implantation of the applicators 38 can here be calculated by the control facility 24 from the 3d image dataset of step s 20 or s 22 obtained in the op . it is then possible to move toward the position automatically and / or at the press of a button in a step s 30 . the position is optimal in the sense that the physician can identify the position of the applicators 38 on the 2d projection image dataset ( 2d ) as far as possible e . g . free from congruence . during the implantation the physician can then execute step s 30 multiple times and so monitor the position of the applicators 38 . after the implantation ( post - imp 3d ) a further 3d image dataset is obtained , still intraoperatively , with the imaging facility 16 in a step s 32 and the position of the applicators 38 is checked . step s 28 can be executed again here , so that the associated dose distribution calculated by simulation is again displayed for the intraoperatively determined 3d image dataset . the physician receives a visual result of the accuracy and if necessary can make a correction directly . for the flow trace according to fig2 no final check outside the operating room is necessary , as is the case in conventional operations . the monitoring by the markers in step s 28 or by the final check in step s 32 already provides confirmation of the correct position of the applicators 38 . now to conclude the operation radioactive material can be introduced into the applicators 38 in a step s 34 . this is provided for permanent irradiation ( ld perm ). provision can also be made to take the patient into the described afterloading room after the operation in a step s 36 and to temporarily irradiate him there ( ld temp ). in the various described variants of the flow trace an additional check on the position of the applicators 38 for example in a computed tomography system and the associated multiple repositioning of the patient become unnecessary . the intraoperative variant is used , resulting in a saving in time , resources , costs and dose . moreover the risk of an infection or of an internal injury caused by the applicators 38 is reduced for the patient 10 . furthermore , the accuracy of the positioning of the applicators 38 is increased , because the physician is given additional opportunities to correct the position with little effort . the example shows how the workflow in brachytherapy is optimized and completed . all necessary steps can be performed with the aid of an application if steps s 12 , s 20 , s 22 , s 26 or s 30 / s 32 , s 28 are united in one application ( combination of software and hardware ). it is also easy to form interfaces to an existing hospital information system , in order additionally to automate the ordering of radioactive material and the scheduling for the operation . overall the result is an automation system which can be adjusted and / or altered individually by the physician at any time . the intraoperative imaging ( 2d and 3d ) enables an up - to - date statement about the precise position of the organs 32 , 34 , 36 is made during the operation . a check on the position of the implanted applicators 38 is likewise effected intraoperatively . no further steps apart from the operation are necessary for checking the position .
a navigation device for brachytherapy is provided . the navigation device has a 3d imaging facility which can be moved relative to an operating table , and which is designed to obtain a 3d image dataset intraoperatively for a region of the body of a patient positioned on the operating table which is to be irradiated radioactively using at least one applicator . the navigation device has a control facility which is linked to the imaging facility and is designed to generate a volume model of the region of the body , in which volume model the at least one applicator is emulated in the position indicated by the position data , from the 3d image dataset and from position data for a spatial position of the at least one applicator .