according to a preferred embodiment of the invention discussed below , a method is provided in which an x - ray system is adjusted for the examination procedure , such as providing a proper angle for the c - arm , position of the patient table , etc . fig1 a - c illustrate a vessel 12 of a subject . the subject is injected with a contrast agent , and x - ray projections xr are acquired with an ecg triggering of the cardiac vessel to be examined in at least two viewing angles ( optimally 90 ° from one another — shown are x , y and x , z planes ), i . e ., either in the biplanar mode or two successive exposures or rotation angiography . regarding the use of x - ray projections , the x - ray projections xr are acquired with contrast agent injection in order to conduct a 3d reconstruction vol ( fig3 ) of the geometry of the vessel 12 or of the lesion 30 to be examined . the x - ray projections xy are acquired without contrast agent injection in order monitor the progress of the pullback . during the pullback , a monoplanar acquisition is sufficient ; however a biplanar acquisition also possible . the position of the patient table may thereby not change . a 3d reconstruction vol of the cardiac vessel 12 can be created using the at least two x - ray projections xr described above using , for example , the interventional cardiac 3d ( ic3d ) method , which allows a 3d volume vol image to be created based on two or more different projections xr ( x , y ), xr ( x , z ) such that the 3d image vol can be visualized from any chosen angle . optionally , various parameters of the vessel 12 may be quantified in the 3d representation vol . the procedure then involves determining , by the doctor , the start point p 1 ( x 1 , y 1 , z 1 ) of the pullback of the intravascular modality at time or trigger t 1 and then acquiring two x - ray projections ( optimally positioned with respect to one another by approximately 90 °) xr 1 ( x , y ), xr 1 ( x , z ) in which the catheter tip 16 is visible . using the pullback method and by acquiring the intravascular images vasc , the pullback speed thereby monitored and simultaneously the ecg signal or ecg triggering 130 ( fig3 ) for ecg registration is acquired with the 3d reconstruction . fig1 a - c and 2 a - c illustrate the starting point p 1 and two subsequent stages during the pullback p 2 , p 3 . optionally during the pullback , x - ray projections xr ( without contrast agent injection ) may be simultaneously acquired in which the tip 16 of the intravascular catheter 14 is visible ( for monitoring of the pullback ). during the pullback , the system creates a representation of the 3d reconstruction vol ( acquired in the previously described step ) of the vessel 12 and of a marker 16 whose position in the 3d lumen 12 corresponds to the position of the tip 16 of the intravascular catheter 14 in quasi - real time . the co - registration begins with the registration of the start point p 1 of the pullback . registration of the catheter tip 16 at the start point p 1 of the pullback is indicated with a marker 16 in the 3d reconstruction vol of the vessel 12 . the two x - ray projections xr 1 ( x , y ), xr 1 ( x , z ) are acquired ( without a contrast agent injection ) at approximately 90 ° from one another at the start point p 1 ( x 1 , y 1 , z 1 ) of the pullback , in which x - ray projections the catheter tip 16 is visible , and are registered with the 3d representation vol 1 ( x , y , z ) using the c - arm setting ( the position and angulation ). the catheter tip 16 is automatically detected on these x - ray projections xr 1 with a computer program or is provided by the user ( by selecting , with e . g ., a mouse 160 click , on the x - ray projection xr 1 ); its position in the 3d space p 1 ( x 1 , y 1 , z 1 ) is detected and indicated in the 3d representation vol 1 of the vessel 12 ( in the vessel lumen ). co - registration continues as the pullback continues ( time / trigger points t 2 , t 3 ). when the position of the start point p 1 ( x 1 , y 1 , z 1 ) of the pullback is known in the 3d representation vol , the further positions p 2 ( x 2 , y 2 , z 2 ), p 3 ( x 3 , y 3 , z 3 ) of the catheter tip 16 can be derived using the passed route of the catheter tip 16 relative to the start point p 1 ( x 1 , y 1 , z 1 ). this route may be provided by the pullback speed ( mm / s ) and the elapsed time or image rate ( images / s ) and image number . with the assumption that the catheter tip 16 is always located on the center line of the vessel lumen 12 or via the application of a centering catheter device 14 , the catheter position p is indicated in quasi - real time (“ quasi ” implying after calculation of the passed route ) in the 3d representation vol by a marker on the center line of the vessel lumen 12 . ekg - synchronous image data / information may be utilized . referring to fig3 , the 3d reconstruction vol is created by a 3d reconstructor 140 from the two x - rays xr ( x , y ), xr ( x , z ) of the two orthogonal x - ray imagings 110 , 120 created from the ekg - registered intravascular vasc ( 100 ) and x - ray images xr may then be archived in an image store 170 and / or transmitted to a workstation 180 for further analysis , review , and / or processing . a co - registration program 190 may then be utilized on the workstation 180 to review the images vasc , vol . when a user with a pointing device 210 selects or clicks a location in the vessel on the 3d reconstruction 220 of the vessel displayed on the monitor 200 , the corresponding intravascular image vasc is automatically , additionally displayed 230 . the user can thus scroll through the entire vessel image 220 and the corresponding intravascular image 230 is automatically displayed . regarding the intravascular image data set vasc 1 , 2 , 3 that is , for example , acquired with an ivus or with an oct catheter 14 , 100 , the pullback method consists of initially positioning the catheter tip 16 distal from the lesion 30 in the vessel 12 and then drawing the catheter back with a controlled speed , both proximal to and through the lesion 30 . the catheter tip 16 simultaneously acquires intravascular images vasc or information of the vessel 12 and displays these to the user . this method serves to provide to the doctor morphological information about the lesion 30 and the vessel wall that is complementary to the information about the anatomy acquired from the x - ray projections xr . other catheter - based invasive methods in which a pullback occurs ( such as optical coherence tomography ( oct ), optical frequency domain imaging ( ofdi ), intracardiac echocardiography ( ice ), pressure wire , angioscopy , near - infrared fluorescence ( nirf ) imaging , molecular imaging , intravascular magnetic resonance ( mr ) and other optical based cross sectional imaging techniques can also be used and co - registered . for the purposes of promoting an understanding of the principles of the invention , reference has been made to the preferred embodiments illustrated in the drawings , and specific language has been used to describe these embodiments . however , no limitation of the scope of the invention is intended by this specific language , and the invention should be construed to encompass all embodiments that would normally occur to one of ordinary skill in the art . the present invention may be described in terms of functional block components and various processing steps . such functional blocks may be realized by any number of hardware and / or software components configured to perform the specified functions . for example , the present invention may employ various integrated circuit components , e . g ., memory elements , processing elements , logic elements , look - up tables , and the like , which may carry out a variety of functions under the control of one or more microprocessors or other control devices . similarly , where the elements of the present invention are implemented using software programming or software elements the invention may be implemented with any programming or scripting language such as c , c ++, java , assembler , or the like , with the various algorithms being implemented with any combination of data structures , objects , processes , routines or other programming elements . furthermore , the present invention could employ any number of conventional techniques for electronics configuration , signal processing and / or control , data processing and the like . the particular implementations shown and described herein are illustrative examples of the invention and are not intended to otherwise limit the scope of the invention in any way . for the sake of brevity , conventional electronics , control systems , software development and other functional aspects of the systems ( and components of the individual operating components of the systems ) may not be described in detail . furthermore , the connecting lines , or connectors shown in the various figures presented are intended to represent exemplary functional relationships and / or physical or logical couplings between the various elements . it should be noted that many alternative or additional functional relationships , physical connections or logical connections may be present in a practical device . moreover , no item or component is essential to the practice of the invention unless the element is specifically described as “ essential ” or “ critical ”. numerous modifications and adaptations will be readily apparent to those skilled in this art without departing from the spirit and scope of the present invention .
a method and appertaining system permit a co - registration between points in a three - dimensional model of a vessel and vascular images obtained by an imaging catheter within the vessel at the respective points . the three - dimensional model is created by utilizing information from at least two external two - dimensional images produced by , e . g ., one or more x - ray devices . the three - dimensional model is displayed on an analysis workstation , and a user may view the vascular images at particular points by selecting the appertaining points on the three - dimensional model .