Patent Publication Number: US-11026648-B2

Title: Volume presentation for planning a location of an injection point

Description:
CROSS-REFERENCE TO PRIOR APPLICATIONS 
     This application is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2017/073973, filed on Sep. 22, 2017, which claims the benefit of European Patent Application No. 16190262.2, filed on Sep. 23, 2016. These applications are hereby incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The technical field generally relates to visualization of a region of interest by way of a volume presentation and planning a location of an injection point. In particular, the volume presentation allows planning of an injection point for a transarterial catheter embolization procedure. 
     BACKGROUND OF THE INVENTION 
     A technique called transarterial catheter embolization (TACE) is used to deliver cancer treatment directly to a tumor through minimally-invasive means. A combination of chemotherapy drugs and embolization material is used to block off (embolize) the blood supply to the tumor. 
     The TA(C)E procedure is typically performed in the “angio-suit”. By puncturing the common femora artery in the right groin or the radial artery in the wrist, a catheter is guided through the arterial system near the area to be treated. 
     Here, a micro catheter is guided in the proper distal artery that supplies the tumor, where the agent is pushed into the tumor. This (super) selective embolization is done to maximize the amount of chemotherapeutic/embolic agent that is directed to the tumor and to minimize the amount of the therapeutic material that could damage the normal tissue. 
     Important aspects to the success of the TA(C)E routine are the detection of all the tumors, full coverage of the detected tumors with the therapeutic drug, embolization of all the feeding arteries, optimized selectivity to limit damage the normal tissue, particularly liver tissue. It is desirable to optimize the injection(s) for full feeder embolization and lesion coverage, with optimal selectivity. 
     The optimal visualization of tumor feeding blood vessels and parenchymal space are important to determine catheter position and injection parameters for (chemo) embolization drug delivery, and can ultimately impact the treatment outcomes. 
     The development of C-arm cone-beam computed tomography (CBCT) has greatly aided in the detection and visualization of tumors. The introduction of dual phase cone beam CT has led to an increase in detection of liver tumors. 
     A description of the use of dual phase CBCT is provided in “Evaluating tumors in transcatheter arterial chemoembolization (TACE) using dual-phase cone-beam CT”, Minimally Invasive Therapy &amp; Allied Technol. 2011 September; 20(5): 276-281, doi: 10.3109/13645706.2010.536243. Here, C-arm cone-beam computed tomography (CBCT) is used to visualize tumor-feeding vessels and parenchymal staining during transcatheter arterial chemoembolization (TACE). A feasibility study is presented of software that allows a CBCT system to capture the two phases using only one contrast injection. The software enables acquisition of two sequential, back-to-back, CBCT scans (dual-phase CBCT, DPCBCT) so both tumor feeding vessels and parenchyma are captured using only one contrast injection. Image acquisition can occur with both clockwise and counter-clockwise C-arm rotations, image reconstruction of both scans occurs after the completion of both scans, and both reconstructed datasets are displayed side-by-side. By displaying the scans side by side, the software allows for simultaneous cine viewing. The software disclosed is considered to allow improved information about the number and distribution of tumors. 
     Following vessels in slice presentations can be cumbersome because of their discontinuity, which necessitates mental interpretation while browsing through the slices. A 3D volume presentation would be advantageous since the whole vessel tree branching structure is presented in one view. However, a highly detailed volume presentation provides an overload of visual information and can be processing intensive, whilst a lower detail presentation may not be able to visualize all lesions/feeders. Yet, the smallest detail may influence the treatment to avoid future recurrences. 
     Thus, it is desired to provide a visualization technique that allows structures, such as lesions and feeders, in a region of interest to be identified with increased accuracy in a processing efficient way to allow for practical implementation. It is further desirable to provide a visualization technique that allows for enhanced planning of where to position an injection point to optimally treat a lesion. 
     WO 2009/109887 A1 discloses a method of image processing of images of a tube system. A tube model is gathered from a specific tube data set. A user may select a virtual injection point of a medium, define a direction with respect to the virtual injection point, and simulate a dynamic flow of the medium starting at the virtual injection point. At least two dynamic images are generated and displayed, so as to provide a three dimensional visualization of a simulated medium flow. 
     SUMMARY OF THE INVENTION 
     Hence, there may be a need to provide an improved and facilitated way of visualizing imaging data for planning at least one location of an injection point. 
     Generally, embodiments of the present invention relate to a combined volume presentation mode where, based on at least one indicated injection point, distal end features, behind the injection points, will be enhanced by means of a dedicated, high detail, injected volume rendering implementation. An injection simulation can be run based on an injection from the at least one indicated injection point. An injection volume representing a volume of tissue reached by the injection can be determined based on the injection simulation. The combined volume presentation visualizes the injection volume using the high detail volume rendering implementation. 
     The object of the present invention is solved by the subject-matter of the independent claims; wherein further embodiments are incorporated in the dependent claims. It should be noted that the following described aspects of the invention apply also for the image processing system, for the imaging system, for the medical system and for the computer implemented method as well as for the computer program element and the computer readable medium. 
     Methods, image processing systems, systems and computer programs are provided for visualization of a region of interest and planning a location of at least one injection point for a medical procedure. In particular, at least one volume of imaging data for a region of interest is received. At least one virtual injection point is obtained. The at least one injection point indicates a location in a network of blood vessels for at least one injection. First and second rendering modules are controlled to construct a combined volume presentation including a first volume region rendered by a first rendering module at a relatively low level of detail and a second volume region is rendered at a higher level of detail by a second rendering module. The first and second volume regions are designated based on the at least one virtual injection point. 
     Such a combined volume presentation allows a more detailed volume of the region of interest to be displayed for a relevant region relative to at least one virtual injection point and a lower detailed volume for other regions to be displayed so that a processing efficient and user intuitive presentation can be provided that allows accurate identification of structures, such as lesions and feeders, in a relevant region relative to the at least one virtual injection point. 
     In an embodiment, a user selection of the at least one virtual injection point is received. Accordingly, a user is able to interactively try out different injection points through a user interface module to control visualization of features relative to the virtual injection point. The user input may be through a selection of a point in a volume presentation. 
     The second volume region is located in the combined volume presentation downstream of the at least one virtual injection point relative to a direction of blood flow in the network of blood vessels. Accordingly, an injection area relative to a virtual injection point is viewed in a detail enhanced way. 
     In an embodiment, the imaging data dual phase computed tomography imaging data including arterial phase imaging data and delayed phase imaging data. The first rendering module renders the arterial phase imaging data and the second rendering module renders registered arterial phase imaging data and delayed phase imaging data. The arterial phase imaging data is enhanced by the delayed phase imaging data and is able to show distal features relative to an injection point more clearly than in a single phase embodiment. 
     The first and second rendering modules may alternatively operate on the same volume of imaging data, yet render the imaging data at different levels of detail. This embodiment allows registration and dual phase enhancement processing to be avoided to reduce processing requirements as compared to the dual phase embodiment. 
     At least one adapted virtual injection point may be obtained based on a received command to add at least one virtual injection point, delete at least one virtual injection point, or to move at least one virtual injection point. The first and second rendering modules are controlled to construct an adapted combined volume presentation including first and second volume regions, respectively rendered by the first and second rendering modules, designated based on the at least one adapted virtual injection point. Accordingly, the combined volume presentation can be iteratively adapted by changing at least one virtual injection point. The combined presentation is able to show in high detail an injection area downstream of the at least one virtual injection point and the injection area will adapt depending upon selection of virtual injection points. This provides a powerful planning tool. The at least one adapted virtual injection point may be user selected. 
     In an embodiment, an injection simulation module simulates an injected region from each at least one virtual injection point. The first and second volume regions of the combined presentation are designated based on the injected region. In particular, the simulation module is able to produce a volume map labelling voxels of the imaging data as being reached by an injection from each at least one virtual injection point based on an injection simulation so as to derive the injected region. The area rendered by the first rendering module and the area rendered by the second rendering module can be designated based on the volume map. An injection simulation based solution provides a processing efficient, yet effective way to show an injected region in the combined volume presentation and thus appropriately demarcate the high and low detail areas of the combined volume presentation. 
     In an embodiment, the injected region is simulated from each at least one virtual injection point by processing the at least one volume of imaging data using a virtual perfusion algorithm that estimates injection material perfusion from each at least one virtual injection point. An exemplary virtual perfusion algorithm is based on computation of a geodesic potential distance map that encodes a probability distance that any location in the data is from a reference point following blood vessels. The probability distance is determined based on arc length distance and a potential term that mathematically favors paths that follow more intense imaging data (i.e. blood vessel in imaging data obtained from contrast enhanced imaging). Such a geodesic potential distance map allows the injected region to be simulated without processor intensive segmentation of the imaging data. 
     In an embodiment, the combined volume presentation is constructed to include a highlighted volume region that has been graphically highlighted to indicate tissue reached by an injection from each at least one virtual injection point. The highlighted volume region may be based on the simulation. This feature of the present disclosure allows fast checking of the perfusion result of a candidate injection. 
     The following features provide further visualization options that can improve assessment and/or determination of injection points for a medical procedure such as an embolization procedure in a processing efficient way. 
     In an embodiment, an injected region is determined based on the at least one virtual injection point non-injected vessels are determined in a neighborhood region to the injected region. The first and second rendering modules may construct the combined volume presentation so that the second volume region includes the injected region and the non-injected region and/or the non-injected vessels are graphically highlighted. This provides a check for an operative that a selected virtual injection point is not missing important feeder vessels leading to a lesion in a neighbor region defined around the injected region. The neighborhood region may be determined based on a scaler enlargement of the injected region. The non-injected vessels can be found using path finding logic and the neighborhood region. 
     In an embodiment, a segmentation module segments a lesion from the imaging data. The lesion may be graphically highlighted in the combined volume presentation. 
     In an embodiment, an automatic feeder determination module determines at least one feeder vessel to a lesion. A feeder path along the at least one determined feeder vessel to the lesion is graphically highlighted. The feeder path may be determined using a path finding algorithm. 
     In an embodiment, an automatic injection member path determination module obtains a location of a distal end of a catheter that feeds an injection device and automatically determine an injection member path from the location of the catheter distal end to the virtual injection point through the network of blood vessels. The injection member path is graphically highlighted in the combined volume presentation. The injection member path may be determined using a path finding algorithm. 
     In an embodiment, a rendering selection module allows a user to select at least one visual aspect of at least one of the first and second rendering modules. In this way, the detailed area of the combined volume presentation can be visually enhanced by adjusting visual setting of the second rendering module. 
     In an embodiment, an automatic virtual injection point determination module automatically determines the at least one virtual injection point based on a location of a lesion obtained from the at least one volume of imaging data and a path to the lesion. The first and second volume regions are designated based on the automatically determined at least one virtual injection point. The path to the lesion may be automatically determined. Further, the path from a catheter to the automatically determined virtual injection point can be automatically determined. In this way, a user can merely select a lesion in a visualization of the imaging data and the path to the lesion and the virtual injection point can be automatically determined. Further, the dual detail rendering can be determined based on the automatically determined virtual injection point along with graphical highlights of a path from a catheter to a virtual injection point all based on a single selection. By automatically determined herein, it is meant that the features are determined through computer based data processing using suitable computer algorithms. 
     In various embodiments, the second rendering module renders at a higher spatial resolution than the first rendering module. 
     Also disclosed is a computer program element adapted to implement an image processing system as described herein or adapted to perform the method steps described herein when executed by at least one processor. 
     A computer readable medium having stored the computer program element. 
     These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  is a schematic view of a medical system including a transarterial medical device, an imaging machine, a display unit and an image processing system; 
         FIG. 2  is a block diagram of modules of the image processing system; 
         FIG. 3  is a data flow diagram for processing source imaging data to a combined volume presentation according to a first embodiment of the methods disclosed herein; 
         FIG. 4  is a data flow diagram according to a modified embodiment of the methods disclosed herein to that of  FIG. 3 ; 
         FIG. 5  is a series of volume presentations according to the present disclosure; 
         FIG. 6  illustrates further volume presentations according to the present disclosure; and 
         FIG. 7  illustrates another volume presentation according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     The following disclosure is particularly provided with reference to TACE procedures, particularly for embolization of liver tumors. However, other applications of the present visualization and injection planning methods and systems are possible. 
       FIG. 1  is a schematic view of a medical system  32  comprising an extracorporeal imaging machine  36 , an image processing system  10 , a display unit  24 , a medical device  16  and a patient support table  34 . 
     The imaging machine  36  is configured for generating imaging data of a patient supported on a table  34 . The imaging machine  36  comprises a detector  20  and an X-ray generator  22 . The imaging machine  36  is configured for X-ray imaging. The imaging machine  36  may be configured for angiographic imaging. The imaging machine  36  is configured for generating three-dimensional imaging data. In a specific embodiment, the imaging machine  36  is a computed tomography (CT) imaging machine having a C-arm configuration, with the detector  20  at one end of the C-arm and an X-ray generator  22  at the other end of the C-arm. In the specific embodiment, the imaging machine  36  is a cone beam computed tomography imaging machine (CBCT) configured for executing dual phase CT measurements to obtain dual phase CBCT imaging data. 
     The image processing system  10 , such as a general purpose computer, is operably connected to the imaging machine  36  controls operation of the imaging machine  36  for performing scans to obtain imaging data and processes the imaging data from the imaging machine  36 . The processed imaging data may be presented on the display unit  24  of the medical system  32 . 
     The image processing system  10  comprises at least one processor  30 . The processor  30  is operably connected to a memory  28 . The processor  30  and the memory  28  may be connected through a bus  38 . The processor  30  may be any device capable of executing program instructions, such as one or more microprocessors. The memory may be any volatile or non-volatile memory device, such as a removable disc, a hard drive, a CD, a Random Access Memory (RAM), a Read Only Memory (ROM), or the like. Moreover, the processor  30  may be embodied in a general purpose computer. 
     The image processing system  10  comprises a number of modules  100 - 130 , shown in detail in  FIG. 2 , for executing the image processing systems and methods described herein, particularly with reference to  FIGS. 3 to 6 . As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. In particular, the modules  100 - 130  described herein include at least one processor, a memory and computer program instructions stored on the memory for implementing the various functions and processes described with respect to the modules  100 - 130 . Although separate modules  100 - 130  are described herein for particular functions, this does not exclude an integrated topology. Further, the shown modules  100 - 130  may be divided into further sub-modules. The modules  100 - 130  are in communication with one another as necessary to implement the features, processes and systems described herein. 
     A display generation module  40  is also operably connected to the processor  30  through the bus  38 . The display generation module  40  is configured to generate, with the processor  30 , display of images for the display unit  24 . The display generation module  40  may be implemented by hardware, software or a combination thereof. The display generation module  40  makes use of first and second rendering modules  102 ,  104  and other modules (shown in  FIG. 2 ) for displaying the combined volume presentation described herein. The display generation module  40  may be included as programming instructions for the processor  30  and stored on the memory  28 . The display unit  24  may be any monitor, screen, or the like suitable for presenting a graphical user interface (GUI) capable of presenting medical images. 
     In the shown embodiment, the imaging machine  36  is operably connected to the processor  30 . The imaging machine  36  obtains imaging data; which data is provided to the processor  30  for processing to create a three dimensional volume presentation of a region of interest of a vascular network via the display generation module  40 . The three dimensional volume presentation may then be presented on the display unit  24 . 
     The memory  28  has encoded thereon, at least one computer program  44  or computer program element  44 , providing instructions which are executable by the processor  30  to process images from the imaging machine  36 . In addition to the computer program  44  for processing the imaging data for presentation on the display unit  24 , a computer program  44  is also provided that performs a combined three dimensional volume presentation of a region of interest as described herein, particularly with reference to the data flow diagrams of  FIGS. 3 and 4  and with reference to the presentations and methods described with respect to  FIGS. 5, 6 and 7 . 
       FIG. 1  discloses a medical system  32  comprising the image processing system  10 , the CBCT imaging machine  36  for obtaining CBCT imaging data, the TACE device for delivering embolization material at an injection point, a tracking system  35  for tracking a position of a reference part, usually the distal end, of the TACE device  16 , and a display unit  24  for displaying a combined three dimensional volume presentation. The image processing system  10 , the CBCT imaging machine  36  and the tracking system  35  can be considered as comprising in a general imaging system. 
     The TACE device  16  comprises a catheter (not separately shown) that is able to navigate through a vascular network from an entry point to a position adjacent a target lesion. The TACE device  16  includes an injection member that can be extended from a distal end of the catheter to an injection point and can be operated to injection embolization material. The injection member may be a micro catheter disposed within the delivery catheter. The embolization material may include blood vessel occluding agents such as beads and/or microspheres and optionally other drugs such as cancer treating drugs and chemotherapy agents. For example, the TACE device  16  can be operated to inject lipiodol, drug-eluting beads, and Yttrium-90 radioembolizing microspheres. 
     The tracking system  35  may comprise an image based tracking system in which the two dimensional catheter tip is automatically detected in live fluoroscopic images. By projecting the tip position on a three dimensional volume presentation, a three dimensional position of the tip can be established. Accordingly, the tracking system  35  of the present embodiment allows automatic establishment of a reference point of the TACE device  16 , particularly a catheter thereof, through image analysis techniques. 
     According to the present disclosure, the medical system  32  is useful for assisting a TACE procedure. The TACE device  16  is positionable at a target site of a region of interest in order to inject embolization material (and optionally also other tumor treating drugs such as chemotherapy agents) for occluding flow of blood to the target lesion. In order to minimize collateral damage and maximize lesion treatment, the imaging machine  36  and the image processing system  10  are operable, through the various modules described further below, with the TACE device  16  in situ. The present imaging system allows generation of a combined volume presentation by way of first and second rendering modules  102 ,  104  ( FIG. 2 ) operating two different transfer functions: a low detail transfer function to visualize the main vessel structure proximal to a candidate injection point, and a high detail transfer function to visualize small details from the injection point up to and including a tumor area. In one implementation, the low-detail visualization is based on an arterial phase volume and the high-detail visualization is based on the enhancement phase volume of dual phase imaging data obtained by the imaging machine  36 . The candidate injection point can be user selected through a user interface module  108  ( FIG. 2 ) or automatically determined through an automatic virtual injection point determination module  118  ( FIG. 2 ). More than one virtual injection point may be selected. Virtual injection points can be added, deleted or moved and the image processing system  10  will adapt the displayed combined presentation accordingly. The two levels of detail provided by the combined presentation described herein provide processing efficient, enhanced visualization for a user of the outcome of a corresponding medicament injection for planning one or more injection points for treatment of a target lesion. Once the planning is deemed satisfactory through use of the present imaging processing system  10 , the TACE device can be correspondingly operated to inject embolization material at the proposed injection points, possibly through use of imaging guidance by way of the tracking system  35 . 
     Modules of the processing system  10 , data flows executed by such modules and visualization possibilities enabled by the present disclosure will now be described in detail with reference to  FIGS. 2 to 7 , whilst continuing to refer to the medical system  32  of  FIG. 1 . 
     With reference to  FIG. 2 , the image processing system  10  includes a data receiving module  100  that is configured for receiving tomographic imaging data. The imaging data is obtained by the imaging machine  36 . The tomographic imaging data may comprise first and second volumes of imaging data including respective phases of a dual phase imaging procedure. Alternatively, the image processing system  10  operates without a dual phase procedure in which case a single volume of imaging data can be received by the data receiving module  100 . The imaging data includes imaging data covering a region of interest (such as including a liver or part thereof), at least one target lesion, a distal end of the TACE device  16  in situ in a vascular network and adjacent the target lesion. The imaging data is contrast enhanced so that the vascular network can be readily contrasted from other tissue. The imaging data is made up of voxels of imaging data (data points arranged in three dimensions) and each voxel comprises at least a value representing intensity of X-ray radiation attenuation, usually measured in Hounsfield units (HU). 
     The image processing system  10  includes first and second rendering modules  102 ,  104 . The first and second rendering modules  102 ,  104  execute known image processing techniques to render a two dimensional projection from a three dimensional volume of imaging data for display by the display unit  24 . Since the rendering techniques provide a projection of the three dimensional volume of imaging data, a sense of a three dimensional volume being constructed is provided on the display unit  24 . 
     The first rendering module  102  is a lower detail renderer than the second rendering module  104 . That is, the first rendering module  102  has a lower detail voxel transfer function than the second rendering module  104 . In particular, the first rendering module  102  samples imaging data and renders such imaging data at a lower level of spatial resolution than the second rendering module  104 . For example, the first rendering module  102  may operate at a low resolution of 384{circumflex over ( )}3 and the second rendering module may operate at a higher resolution of 512{circumflex over ( )}3 for the same volume of tissue. The imaging data obtained by the imaging machine  36  may be at the higher resolution of the second rendering module  104  or higher and may be sampled at a lower resolution by the first rendering module  102 . Alternatively, the imaging data may be provided through some sampling module so that the imaging data is received by the data receiving module at different spatial resolutions (high and low), which are used by the different rendering modules  102 ,  104  to render the imaging data at different spatial resolutions. 
     The first and second rendering modules  102 ,  104  have different spatial resolutions, and may additionally have different rendering methods, contrast/brightness transfer functions, color schemes and/or white space speed optimization methods. The first and second rendering modules  102 ,  104  may allow for independent control, such as user control, of visual aspects of rendering settings including contrast/brightness, rendering option (Gradient, Max Intensity Projection, Volume rendering and/or pre integrated volume presentation etc.). The user may be able to control at least one visual aspect of at least one of the first and second rendering modules  102 ,  104  selected from contrast/brightness level and rendering method including at least one of maximum intensity projection, volume rendering, and pre-integrated volume presentation. The user may control rendering settings of the first and second rendering modules  102 ,  104  through a user interface module  108  as described below. 
     The first and second rendering modules  102 ,  104  are configured for constructing the combined volume presentation through the display generation module  40  by making use of a framebuffer (not shown). The combined volume presentation has a high detail region constituting a projection rendered by the second rendering module  104  at higher resolution and a low detail region constituting a projection rendered by the first rendering module  102  at lower resolution. The higher detail and lower detail projections are demarcated based on at least one virtual injection point as described in further detail in the following. 
     In one embodiment, dual phase imaging data is utilized. That is, an arterial phase of imaging data is acquired for the region of interest by the imaging machine  36  at an early phase after contrast injection and a delayed (parenchymal enhancement) phase of imaging data is acquired for the region of interest at a delayed phase of the region of interest. The early and delayed phases of volumetric data are acquired by time spaced scanning operations by the imaging machine  36 , with the delayed scan executed at least 5 or 10 seconds after completion of the early phase scan. In such an embodiment, the first rendering module  102  is configured to render the early phase imaging data, i.e. the arterial phase imaging data. Further, the image processing system  10  comprises a dual phase registration module  120  that is configured to register (warp) the delayed phase volume of imaging data to the arterial phase volume of imaging data in order to compensate for patient/organ motion (e.g. as a result of breathing). The image processing system  10  also comprises a volume enhancement module  122  that is configured to perform parenchymal enhancement of the early phase volume of imaging data with the delayed phase volume of imaging data as registered by the dual phase registration module  120  to produce an enhanced volume of imaging data. That is, the arterial phase volume will be extended or enhanced with delayed phase soft-tissue (tumor blush) enhancement features from the delayed phase volume. The second rendering module  104  is configured to render the enhanced volume of imaging data. 
     However, a less complex embodiment is envisaged by which the first and second rendering modules  102 ,  104  operate on the same volume of imaging data. In such an embodiment, the dual phase registration and volume enhancement modules  120 ,  122  need not be provided. 
     The image processing system  10  comprises a dual rendering combination module  124 . The dual rendering combination module  124  is configured to control an order of rendering of volumes of imaging data by the first and second rendering modules  102 ,  104 . In particular, dual rendering combination module  124  is configured to determine overlapping areas (pixels) rendered by the first rendering module  102  and the second rendering module  104 . The dual rendering combination module is configured to control a rendering order so that the first rendering module  102  renders first, followed by the second rendering module, yet for all overlapping area (pixels), the rendering order is reversed. It has been found that a problem can occur with a conventional rendering order when high and low detail renderings are combined. Volumes are normally rendered and constructed in a back to front (with respect to a viewing direction) order by means of a so called painter&#39;s algorithm. In the painter&#39;s algorithm, the first rendered volume is blended against a black background. For those voxels of the first volume where parts overlap the second volume, black spots can appear. A solution proposed by the present disclosure is to mark these problem voxels in a two dimensional stencil buffer and reverse the rendering order for those overlapping positions. Stencil logic operations are available in graphics libraries like Direct3D or OpenGL. 
     In more detail, the following steps can be implemented by stenciling control within the dual rendering combination module  124  in order to reverse the rendering order where necessary. Let V 10  be a volume of imaging data rendered by the first rendering module  102  and V 12  be a volume of imaging data rendered by the second rendering module  104 . First, render V 10 , then setup stencil control whilst rendering V 12  in order to determine overlapping pixels based on buffer depth. Using a stencil indicating overlapping pixels, the rendering order is reversed where there is an overlap by first rendering V 12  and then rendering V 10 . 
     The image processing system  10  comprises a user interface module  108  that allows for a variety of user controls and selections. The user interface module  108  receives user inputs from an input unit (not shown) such as a touchscreen device, which can include the display unit  24 , a mouse, a keyboard, video captured gesture controls and the like. An example user input can be selection of at least one virtual injection point, which is used by the image processing system  10  to determine a region to be rendered by the second rendering module  104  and a region to be rendered by the first rendering module  102 . The selection of the at least one virtual injection point may be made by positioning a cursor in a displayed volume presentation of the region of interest, in particular by selecting a point in a feeder vessel. Alternatively, the virtual injection points may be processor selected, i.e. automatically selected, such as through the automatic virtual injection point determination module  118  described in greater detail below. The user interface module  108  may also allow user selection of at least one target lesion, such by marking an area in a succession of two dimensional slices of imaging data presented on the display unit  24 . 
     The image processing system  10  comprises an injection simulation module  110 . The injection simulation module  110  is configured to simulate an injection from the at least one virtual injection point and particularly the perfusion of injection material from the at least one virtual injection point. Based on the simulated injection, a downstream region from the at least one virtual injection point can be modelled. The downstream region is used to demarcate a region to be rendered at the higher level of detail and a region to be rendered at the lower detail level. 
     In an embodiment, the injection simulation module  110  is configured to implement a virtual parenchymal perfusion (VP) algorithm to approximate distal vascular territories in a tissue, e.g. liver, region of interest, given the at least one prospective virtual injection point, which uses the imaging data received by the data receiving module  100  as predictive data. In particular, the imaging data used by the simulation algorithm is derived from a three dimensional arterial cone beam computed tomography (CBCT) scan. In one embodiment, the simulation module  110  extracts vascular territories from a vessel-driven geodesic distance map computed from the virtual injection points (positions), which may be user selected. The geodesic potential map results in distance values for each voxel as calculated by the virtual perfusion algorithm. The virtual perfusion algorithm includes a potential term to bias to low distances for contrast injected, i.e. hyper intense, voxels and also tends to lower distance values for voxels closer, in terms of geodesics, to a reference point. Although a vessel driven, geodesic potential algorithm is described in detail herein, other injection simulation algorithms can be used to extract at least one territory or region distal (downstream) to at least one virtual injection point from which a division between the high detail portion and low detail portion of the combined volume presentation can be determined. 
     The algorithm, which computes the geodesic distance map, encodes the connections between a reference location and the closest blood vessels. The reference location is usually taken as a location on the catheter, e.g. the distal end of the catheter, as determined by the tracking system  35 . The reference location that is used may be somewhere on the catheter of the TACE device  16  during contrast acquisition. The exact catheter tip location is not important, as long as it is on the catheter, which is prominently visible in the contrast acquisition volume. Accordingly, description of the reference location as the distal end of the catheter is merely an exemplary embodiment. The reference location may, in an alternative embodiment, be user selected through the user interface module  108 . A vascular territory corresponds to the area distal to a prospective injection point, in the sense of the geodesic metric defined by the geodesic distance map. Such a simulation approach is processing efficient as compared to an explicit vessel segmentation algorithm. 
     In one embodiment, the simulation module  110  is configured to determine a reference catheter point, r, usually corresponding to the distal end of the catheter as determinable from contrast imaging data. The simulation module  110  is configured to compute a geodesic distance map using imaging data and the reference location at the distal end of the catheter. The simulation module  110  is configured to extract at least one vascular territory using the geodesic distance map and at least one virtual injection point. The steps of determining the reference location r, computing the geodesic distance map and extracting the vascular territories are described further below. The processing module  106  is configured to control the second rendering module  104  and the first rendering module  102  to render the dual detail level volume presentation based on the extracted at least one vascular territory. 
     Point r serves as a reference location, i.e. the most proximal injection point, considered in subsequent computations. 
     The vascular-driven geodesic distance map is computed to encode distances from the catheter point r to any location in the imaging data, following blood vessels. Points along or close to the vessels are given low geodesic distance values, while areas outside the vessels result in large geodesic distances. Such a geodesic formulation can be seen as a crude approximation to a fluid simulation. 
     The geodesic distance D r (x) from r to any location x is computed following a minimal path approach [6]: 
                       D   r     ⁡     (   x   )       =       inf     C   ∈     𝒞     r   →   ∞           ⁢       ∫   Ω     ⁢       P   ⁡     (     C   ⁡     (   s   )       )       ⁢   ds                 (   1   )               
where C(s) is a curve of arc-length s in the set of all possible curves C r→x  from r to x, and P(.) is the potential term. The geodesic distance is thus obtained as the minimal cumulative potential connecting r to x.
 
     The potential is designed to favor hyper-intense areas of the imaging data such as contrast injected vessels. An exemplary potential function is: 
                     P   ⁡     (   x   )       =       {     1   -         I   ~     ⁡     (   x   )         1   +            I   ~     ⁡     (   x   )                  }     3             (   2   )               
which corresponds to a sigmoid-shaped function applied to the heuristically normalized image intensity
 
                 I   ~     ⁡     (   x   )       =           I   ⁡     (   x   )       -   M     D     .           
Mean M and deviation D can be empirically set to scale the sigmoid as a soft threshold around the typical pseudo-Hounsfield values of contrasted parenchyma, so that hyper-intense contrast injected vessels obtain positive values.
 
     In order to extract the vascular territory, the geodesic map is used, which encodes the vascular-driven connectivity within the three dimensional imaging data. For any location x, a minimal geodesic path can be traced back to the catheter point, r. Similarly, it is possible to define the vascular territory T(i) distal to a virtual injection point i, which may be user provided:
 
 T ( i )={ x|D   r ( x )≥ D   r ( i ), i∈C   r→∞ *}  (3)
 
where C r→x   ?  is the minimal path from the catheter r to x. This computation can be performed from more than one virtual injection point i to defined a composite vascular territory.
 
     Given the precomputed geodesic map, the extraction of any vascular territory can be performed efficiently, thereby allowing rapid interactive exploration of prospective injection points. 
     The simulation module  110  is configured to output a mapping volume with labels describing which of the voxels of the imaging data will be reached by the proposed at least one virtual injection and which subset of these voxels will contain enhanced contrast information. The labelled subset of voxels with enhanced contrast intensity values allows for the combined volume presentation to highlight the vascular structure carrying injection material from the at least one virtual injection point to a lesion. The overall area of virtual perfusion impregnation in the parenchyma can be utilized to determine that part of the combined presentation that is rendered by the second rendering module  104 . That is, the processing module  106  is configured so that an extracted virtually injected territory as determined by the injection simulation module  110  is rendered by the second rendering module  104 . In one embodiment, the second rendering module  104  renders an extended volume, which contains the arterial phase volume imaging data plus second phase features like tumor blush from the delayed phase volume imaging data. 
     The image processing system  10  comprises a segmentation module  112  that is configured to segment the three dimensional volume of imaging data, e.g. an arterial phase volume, based on trained object models into bone (ribcage) voxels and possibly also organ (liver, kidney) labels. The output is maintained in a mapping volume where for each voxel a label describing the segmentation type is stored. The segmentation module  112  determines the mapping of segmented voxel labels, which is also able to determine a region of interest. The region of interest may determine boundaries for other processing modules, such as for the dual phase registration module  120  and the volume enhancement module  122 . 
     The image processing system  10  comprises a graphics module  126  that is configured to include graphical highlights in the combined volume presentation described herein. For example, any of the following graphical highlights may be added: a lesion region, a lesion boundary, a catheter reference point (e.g. catheter distal end), at least one virtual injection point, an injection member path from a catheter distal end to a virtual injection point, different injection member paths from a catheter distal end to different virtual injection points, an injected region, injection fluid perfusion from at least one virtual injection point, different highlights for injection perfusion from different injection points, feeder vessels to a lesion, vessels in a neighborhood region to a determined injected region etc. Where plural graphical highlights are included they may be presented in a visually differential way such as by different coloring. 
     The combined detail volume rendering disclosed herein allows enhanced visibility of the effect(s) of an injection at a candidate injection site in a processing efficient way. Further, the present disclosure provides a number of presentation control features that will be described further below. 
     The user interface module  108  allows at least one injection point to be inserted and/or manipulated interactively by selecting a location in a vessel in a volume presentation. The volume presentation before virtual injection points are inserted may be constructed at the lower level of detail by the first rendering module  102  to provide a clear, easy to follow presentation of the vessels for a user. Subsequently, an injected volume area from the virtual injection point is computed by the simulation module  110  in addition to vessels within the injected volume area. Based on the injected volume area, a combined presentation will be rendered by sampling (or resampling) the imaging data, with the injected volume area rendered by the second rendering module  104  so as to clearly visualize anatomical features distal of the virtual injection point at the higher level of detail. In the proposed solution, only the vessels and parenchyma area on the injected trajectories are re-sampled and shown in detail. 
     The image processing system  10  comprises an automatic feeder determination module  114  configured to determine feeder vessels to a lesion based on segmented lesion information associated with the imaging data and catheter location (e.g. distal end) information associated with the imaging data. The lesion information may result from an automated segmentation process through the segmentation module  112  or through user identified lesion information through the user interface module  108 . In particular, the user may select boundaries of at least one lesion by in each of a succession of presentations of slices of imaging data. The catheter location information may be based on a user input through user interface module  108  or through automated catheter position information determined based on contrast imaging data. The automatic feeder determination module  114  may implement a path finding algorithm (as known in the art) in order to find all vessel feeders from the lesion to the catheter. In particular, the path finding algorithm may operate determining intersections of candidate feeders with lesions contours. The feeders are identifiable from the contrast enhanced imaging data. Based on the intersections, a connectivity network to the catheter position is calculated and vectorized. The determined feeder vessels may be graphically highlighted in the combined presentation through the graphics module  126 . 
     The image processing system  10  comprises an injection member path determination module  128  configured to determine a path from the catheter distal end to a virtual injection point. Plural paths may be determined for plural virtual injection points. The injection member path determination module  128  uses information on virtual injection point location, which may be user decided through the user interface module  108  or automatically decided through an automated virtual injection point determination module  118  (described below). The injection member path determination module  128  uses a path finding algorithm, e.g. as described above, to determine respective paths from the catheter location to the virtual injection points. The respective paths are graphically indicated in the combined presentation through the graphics module  126  in order to guide a user in positioning the injection member for locating a distal end of the injection member at the location of the virtual injection point. 
     In an embodiment, the injection member path determination module  128  is configured so that when a virtual injection point is added to the volume presentation, the path from the catheter to the virtual injection point, represented by a centerline, is calculated and graphically shown in the volume presentation through the graphics module  126 . To do so, the following injection point logic is implemented. When the added virtual injection point is over the centerline of a previous virtual injection point, the intersection with the three dimensional centerline representation is used as the new injection point position. If no intersection is found and a point on a vessel tree is selected, then the first rendering module  102  is probed by means of a ray casting volume intersection calculation. If no intersection is found, then the second rendering module  104  is tested for intersections. 
     The image processing system  10  comprises an automatic virtual injection point determination module  124  configured to automatically determine at least one virtual injection point. In particular, a user is able to select, through the user interface module  108 , a destination point (usually a destination point within a lesion) in the region of interest in a volume presentation thereof and to select a command to determine at least one virtual injection point. The automatic virtual injection point determination module  124  communicates with the automatic feeder determination module  120  to calculate at least one feeder path from the user selected destination point to the catheter position. The automatic virtual injection point determination module  124  is configured to insert a virtual injection point along each of the at least one feeder path, usually at a preset distance (e.g. 1.5 cm) from the user selected destination point. The preset distance can be user controllable through the user interface module  108 . Further, and optionally, the injection simulation module  110  and the processing module  106  are configured to be responsive to the automatically determined virtual injection points to produce a combined presentation at two levels of detail where the higher and lower levels of detail are designated based on the automatically determined at least one virtual injection point. In this way, at least one virtual injection point, a simulation perfusion therefrom and at least one feeder path from a catheter distal end to each virtual injection point can be determined automatically and graphically highlighted in the combined, dual detail level, volume presentation, with relatively low processing requirements, with a single user selection of a destination point. 
     A further possible feature of the image processing system  10  is shown in  FIG. 2  in the form of neighborhood module  130 . Neighborhood module  130  is configured to scale (enlarge) the area to be shown in the combined presentation in high detail. In particular, an injected area can be derived from the result of an injection simulation performed by the injection simulation module  110 . A neighborhood area can be defined with respect to the injected area. The neighborhood module  130  is configured to process the imaging data to determine all non-injected (as determinable based on output from the simulation module  110 ) contrasted information, arriving from all possible directions and branches, into the neighborhood area. The vessels in the neighborhood area so determined are presented in the combined presentation at the higher level of detail and may also be presented in a different color from the injected area. The neighborhood area can be (increased/decreased) by a preset scalar value relative to the injected area. 
       FIG. 3  shows a data flow diagram illustrating data transformation processes for producing a dual detail level combined presentation as described herein. A number of data processing functions P 1  to P 8  are illustrated, which will be detailed below and related to the previously described image processing system.  FIG. 3  provides a first embodiment of the methods described herein. 
     In the example of  FIG. 3 , a first volume of imaging data V 1  is received corresponding to an arterial phase after contrast agent injection. A second volume of imaging data V 2  is also received corresponding to a delayed phase after the arterial phase. The use of arterial and delayed phase imaging data is preferred, but not necessary as shown by the embodiment of  FIG. 4  (described further below) which does not make use of dual phase imaging data. The imaging data is received through the data receiving module  100 . The first volume of imaging data V 1  can be received in two forms: at high detail (i.e. higher spatial resolution) H and at low detail L (i.e. lower spatial resolution). To receive the first volume of imaging data V 1  at the two detail levels, a sampling process can be used that samples the original imaging data at different resolution levels. 
     In data process P 7 , a first volume rendering is executed at a relatively low level of detail by rendering the low detail, arterial phase volume of imaging data. The process of P 7  is carried out through the first rendering module  102 . The rendered data is output to a presentation control process P 5  described further below. 
     In data process P 1 , the arterial phase volume V 1  will be segmented based on trained object models into bony (ribcage) and organ (liver, kidney) information. Data process P 1  outputs a mapping volume MP, where, for each voxel of the imaging data, a label describing the segmentation type (organ, bone) is stored. The mapping volume MP will also define a region of interest for the data processes P 2 , P 3  and P 6  described below. 
     In data process P 2 , the delayed phase volume V 2 , at the low level of detail or resolution L, will be registered (warped) to the arterial phase volume V 1  at the low level of detail L in order to compensate for patient/organ motion. Such registration processes are known in the art. For example, a known non-rigid deformation and registration process may be utilized. Data process P 2  produces a registered volume of delayed phase imaging data RV 2 . The registration process of P 2  can be executed through the dual phase registration module  120 . 
     In data process P 3 , the arterial phase volume of imaging data V 1  at the high level of detail H will be extended with delayed phase soft-tissue (tumor blush) enhancement features from the registered volume of delayed phase imaging data RV 2 . The data process P 3  produces an enhanced volume of imaging data V 3  that combines the arterial phase imaging data V 1  and the delayed phase imaging data V 2 . The data enhancement process P 3  can be performed through the volume enhancement module  122 . 
     In data process P 8 , the enhanced volume of imaging data V 3  is rendered through the second rendering module  104 . The rendered data is provided to the presentation control process P 5 . 
     In data process P 4 , a reference part of the catheter will be (manually or automatically) determined in the arterial phase volume V 1 . The reference part can be entered through the user interface module  108 , but is usually automatically determined near the distal end of the catheter based on image analysis. Accordingly, the processes described herein are usually carried out during an interventional procedure when the medical device  16 , and particularly the catheter thereof, is in situ, although the methods claimed are concerned with imaging processes and do not extend to catheter placement. The catheter tip position is output from data process P 4  to be utilized in data processes P 5  and P 6 . 
     Data process P 6  performs an injection simulation based on the region of interest received from data process P 2 , the catheter distal end position as a reference point r (as described above) received from data process P 4  and the enhanced volume of imaging data V 3  received from data process P 3 . Further, the data process P 6  makes use of at least one virtual injection location, which has been obtained through data process P 5  described below. The injection simulation can be carried out through the injection simulation module  110 . In data process P 6 , an injected area is simulated as though an injection were made through each of the at least one virtual injection point using the enhanced volume of imaging data V 3 . In one embodiment, the injection simulation process P 6  is based on a notion of geodesic potential field mapping as has been described above with respect to the injection simulation module  110 . Data process P 6  outputs an annotated mapping volume AMV with labels describing which voxels of the volume V 3  will be reached by the proposed at least one virtual injection and which subset of these voxels will contain contrast information (i.e. which of these voxels correspond to blood vessels). The annotated mapping volume AMV is received by the first and second rendering processes P 7  and P 8 . At least one extracted territory or area labelled by the AMV as being reached by the simulated virtual injection is rendered at the higher level of detail by rendering process P 8  and at least one area labelled by the AMV as not being reached by the simulated virtual injection is rendered by the lower detail rendering process P 7 . In some embodiments, the injection simulation may extract a territory reached by the at least one virtual injection and all voxels within that territory may be labelled in the annotated mapping volume AMV as being reached by the virtual injection to ensure a coherent rendering of a continuous area at the higher level of detail. 
     In rendering processes P 7  and P 8 , based on the information in the annotated mapping volume AMV, the corresponding volume areas are re-sampled and visualized by a designated rendering module  102 ,  104 . The two separate rendering processes P 7  and P 8 , executed through separate renderers or rendering modules  102 ,  104 , each have their own spatial resolution, and optionally also at least one of their own rendering method, contrast/brightness transfer function, color scheme, white space speed optimization, etc. where these features can be user controlled. A combined volume presentation can be constructed through suitable control through the presentation control process P 5  in a framebuffer (not shown). 
     In presentation control process P 5 , executed through the processing module  106 , a number of viewing control tasks will be executed. A user input UI can be received through the user interface module  108  to control visualization setting of the rendering processes P 7  and P 8  (e.g. visual transfer function settings). Further, control of which areas of the combined presentation are rendered through rendering process P 7  and which are rendered through the rendering process P 8  is executed by presentation control process by making use of the annotated mapping volume AMV as described above. Further, volume ordering control as has been described above with respect to the dual rendering combination module  124  is performed by data process P 5  and the first and second rendering processes P 7  and P 8  are controlled and the rendered data combined accordingly. Additionally, the inclusion of graphical annotations like the catheter distal end (and perhaps also the elongate catheter itself), virtual injection points, injection member paths, feeder paths, etc. Furthermore, the determination of feeder vessels, determination of injection member paths, and automatic virtual injection points as has been described above with respect to the automatic feeder determination module  114 , the injection member path determination module  128  and the automatic virtual injection point determination module  118  is controlled by data process P 5 . 
       FIG. 4  illustrates a data flow diagram for an alternative embodiment that does not make use of dual phase imaging data.  FIG. 4  provides a second embodiment of the methods described herein. In this case the registration process P 2  and the volume enhancement process P 4  of  FIG. 3  can be omitted. Instead, a single volume of imaging data V 1  can be obtained, which is sent to the low detail rendering process P 7  at a low detail level for the imaging data and which is sent to the high detail rendering process P 8  at a high detail level. Based on at least one virtual injection point obtained through presentation control process P 5 , an injection simulation is run through process P 6  to produce an annotated mapping volume AMV designating at least one injected area that will be reached by an injection performed at the at least one virtual injection point to be rendered by the high detail rendering process P 8 . Further, graphical annotations will be included by the presentation control process P 5  so as to mark in the dual detail, combined presentation at least one virtual injection point, the injected area as determined by the injection simulation of process P 6 , an injection member path from a catheter distal end to the at least one virtual injection point and a catheter distal end. 
     Having described aspects of the image processing system  10  and the data processes with respect to  FIGS. 1 to 4 , operative interactions and volume presentations are described with respect to  FIGS. 5 and 6 . 
       FIG. 5  shows a sequence of volume presentations  300 ,  302 ,  308 ,  310  produced by the image processing system  10  of the present disclosure. 
       FIG. 5( a )  shows an initial volume presentation  300  acting as a starting presentation for user interaction and virtual injection point selection. The volume presentation  300  of  FIG. 5( a )  is rendered in process P 7  by the first rendering module  102  based on the volume of imaging data V 1  after removal of bone based on segmentation process P 1  through segmentation module  112 . Accordingly, the volume presentation  300  of  FIG. 5( a )  is rendered at a relatively low detail level, which allows for a clear volume presentation of the main vessel structures. Where dual phase imaging data is obtained, the volume presentation  300  is of the arterial phase. Further graphically highlighted in the volume presentation is a catheter reference point  304  (as a colored dot in one example) that has been automatically determined in process P 4  through image analysis of fluoroscopic imaging data. As such, the imaging data has been obtained with the catheter in situ and the volume presentation  300  is useful for planning an embolization injection from an injection member extendable from the catheter. 
     In  FIG. 5( b ) , a volume presentation  302  is shown in which a lesion  303  has been graphically highlighted (as a colored portion with a clear outer boundary in one example) through the graphics module  126 . The lesion has been identified through user marking of outer bounds thereof in a presentation of two dimensional, orthogonal slices of the imaging data V 1 . The volume presentation  302  further shows graphics illustrating results of automatic feeder determination through the automatic feeder determination module  114 . In particular, different colored lines  305 ,  306  are included to illustrate paths from the catheter reference point  304  to the lesion  303  that includes all available feeder vessels. The volume presentation  302  is produced by the first rendering module  102  at the lower level of detail. Like  FIG. 5( a ) , the volume presentation  302  does not yet include dual detail levels as a virtual injection point has not yet been selected. 
     In  FIG. 5( c ) , a volume presentation  308  is shown that has combined detail levels according to various embodiments of the present disclosure. One virtual injection point  307  is selected in one of the feeder vessels illustrated by line  305  in  FIG. 5( b ) . The injection point  307  is user selected in the presentation  302  of  FIG. 5( b )  through the user interface module  108 . An injection simulation from the virtual injection point  307  is run, through the injection simulation module  110 , in process P 6  based on imaging data and the position  304  of the catheter distal end, which results in an annotated three dimensional data mapping AMV noting which voxels are simulated to be reached by material injected at the virtual injection point  307 . Based on the annotated mapping AMV, particularly an injected area derived therefrom, the volume presentation  308  includes a high detail injected area distal to the virtual injection point  307  rendered by the second rendering module  104  in process P 8  and a low detail, non-injected area proximal to the virtual injection point  307  rendered by the first rendering module  102  in process P 7 . The low and high detail areas of the combined presentation  308  are seamlessly integrated with one another in the presentation. Where dual phase imaging data is utilized, the high detail area presents enhanced volume of imaging data V 3  in which the arterial phase volume V 1  has been enhanced by features from the delayed phase volume V 2 . Further, the injected area is graphically highlighted by coloring the injected area with shading based on those voxels that are deemed to be reached by the injection based on the simulation. 
     By way of the automated feeder detection shown in  FIG. 5( b ) , it is possible to reveal that the injection plan of  FIG. 5( c )  encompasses an injection in only one of the two detected feeder vessels. Consequently, an operative can plan a further injection point. The automatically detected feeder vessels can be shown before or after a virtual injection point has been selected to readily reveal any insufficiencies in an injection plan. 
     In  FIG. 5( d ) , a combined volume presentation  310  is illustrated which also has high and low detail areas. Here, a user has selected a first virtual injection point  307 . Further, the second feeder vessel is graphically highlighted at  306  to allow an operative to realize that one of the feeders has been missed. Consequently, a second virtual injection point can be placed in the second feeder vessel  306  though the user interface module  108 . The injection simulation process can re-run so that an injection simulation from both the first virtual injection point  307  and the new, second virtual injection can be performed to determine a revised annotated mapping AMV of the volume(s) of imaging data. The further combined volume presentation can be produced that includes an expanded injected area based on the additional, second virtual injection point as compared to  FIG. 5( d ) , which is rendered at the higher level of detail and which includes graphical highlighting (e.g. color shading) to show the injected area reached by the injections from the virtual injection points according to the simulation. The new combined volume presentation can show additional graphical features. Injection member paths  311  from the catheter distal end  304  to the virtual injection points  307  are shown by different colored lines for injection member guidance purposes. Further, an outer contour of the lesion  303  can be graphically highlighted to allow extent of coverage by the proposed injections to be visualized. The combined presentations  308 ,  310  of  FIGS. 5( c ) and 5( d )  allow the injected vessels, including feeding vessels and the connected lesion area(s), to be visualized by means of a volume render solution that is optimized for higher detailed, lower contrast information. In order to visualize, at high detail, vessels and connecting areas between vessels, a mapping output from the injection simulation can be processed to derive a coherent vascular territory that includes the whole of the injected area, which is then displayed at the high detail level. Accordingly, the injected vessels and parenchyma area on the injected trajectories are shown in high detail, with the remainder of the presentation shown in lower detail to ensure clear visualization and efficient processing. 
     By moving virtual injection points from proximal positions to more distal positions, and in the reverse direction, the effect on the injected vessels and resulting tumor and feeding vessel embolization can be evaluated on the fly to plan optimal injection positions that suitably balances lesion coverage and selectivity. Additionally, the injection result including the total affected area and the injected vessels can be shown in the combined volume presentation and in accompanying orthogonal slices if desired. 
     If not carefully checked, sometimes important feeders, coming from unexpected more proximal branches, can be missed. In  FIGS. 5( a ) and 5( b ) , combined presentations  400 ,  402  that illustrate presentation enhancement by showing not only the injected area in higher detail, but also a neighborhood area as determined by the neighborhood module  130 . In  FIG. 6( a ) , the presentation  400  shows an injected area distal to a virtual injection point  408  at a higher level of detail and colored for ease of visualization than an area proximal to the virtual injection point  408 . Further, graphics are included to highlight the injection member path  407  from a catheter distal end  406  to the virtual injection point. The catheter distal end  406  and the virtual injection point  408  are also graphically illustrated through the graphics module  126 . The injected area is determined based on output from an injection simulation process P 6  (which usually results in a simulated injected three dimensional volume) based on an assumed injection from the injection point  408 . When activated, the neighborhood area module  130  is configured to determine a neighborhood area or volume (such as through a scalar area or volume expansion of the injected area or volume) based on the injected area or volume and to determine all feeders and vessels from the contrast enhanced imaging data in the neighborhood area or volume. The feeders and vessels in the neighborhood area can be determined using path finding processing on the contrast enhanced imaging data. The feeders and vessels in the neighborhood area can be graphically highlighted, such as by a different color from the graphical highlighting in the injected area. The neighborhood area may also be presented at the higher level of detail.  FIG. 6( b )  thus shows additionally graphically highlighted vessels  410  in the neighborhood of the injected area based on neighborhood vessel determination executed by the neighborhood module  130 . This feature aids in an operative avoiding missing relevant vessels for a successful embolization procedure. 
     In  FIG. 7 , a combined presentation  404  is shown having graphically illustrated first and second virtual injection points  420 ,  422  that are user selected through the user interface module  108 . Further, a catheter distal end  428  is graphically illustrated, where the catheter distal end  428  is determined from image analysis (for example). Injection member paths  424 ,  426  have been determined using path logic processing of the imaging data through the injection member path determination module  128 , and extend from the catheter distal end  428  to respective virtual injection points  420 ,  422 . An injected area, downstream of the virtual injection points  420 ,  422 , is graphically highlighted and rendered in relatively high detail. The injected area is derived from an injection simulation performed through the injection simulation module  110 . In this case, the injected area is rendered using a different volume rendering preference than in  FIGS. 5 and 6 . Whilst the second rendering module  104  is still operating at higher detail than the first rendering module  102 , the transfer function (such as the spatial resolution and/or contrast settings) have been adapted to allow the vessels in the injected area to be yet more clearly visualized. Such adaptation of the visualization setting of the first rendering module may be user selectable through the user interface module  108 . 
     In one possibility, the combined volume presentation  404  of  FIG. 7  may be automatically determined simply by clicking on or otherwise selecting a destination point in a visible tumor. That is, usually the core of the (highly vascular) tumor region is partially visible in an initial presentation (such as that shown in  FIG. 5( a ) ), but the access trajectory is usually difficult to figure out. From such a presentation, a destination point can be selected by a user. Alternatively, the destination point can be indicated in an orthogonal slice presentation. Given the selected destination point or location, the access paths (feeders) to the selected destination point in the tumor to the catheter distal end is calculated through the automatic feeder determination module  114 . A virtual injection point can be placed along each feeder at a controllable (preset) distance (e.g. 1.5 cm) from the destination point through the automatic virtual injection point determination module  118 . An injection simulation can be automatically performed for the virtual injection points. As a result, by a single selection of a destination target on the tumor core in  FIG. 5( a ) , the graphical and visualization enhancements shown in  FIG. 7  can be obtained. In particular, the injected area is visualized at higher detail and colored/otherwise graphically highlighted to show the simulated injection, virtual injection points  420 ,  422  can be determined and graphically inserted and injection member paths  424 ,  426  can be determined and graphically inserted. 
     In another exemplary embodiment of the present invention, a computer program or a computer program element is provided that is characterized by being adapted to execute the method steps of the method according to one of the preceding embodiments, on an appropriate processing system. 
     The computer program element might therefore be stored on a computer unit, which might also be part of an embodiment of the present invention. This computing unit may be adapted to perform or induce a performing of the steps of the method described above. Moreover, it may be adapted to operate the components of the above described apparatus. The computing unit can be adapted to operate automatically and/or to execute the orders of a user. A computer program may be loaded into a working memory of a data processor. The data processor may thus be equipped to carry out the method of the invention. 
     This exemplary embodiment of the invention covers both, a computer program that right from the beginning uses the invention and a computer program that by means of an up-date turns an existing program into a program that uses the invention. 
     Further on, the computer program element might be able to provide all necessary steps to fulfil the procedure of an exemplary embodiment of the method as described above. 
     According to a further exemplary embodiment of the present invention, a computer readable medium, such as a CD-ROM, is presented wherein the computer readable medium has a computer program element stored on it which computer program element is described by the preceding section. 
     A computer program may be stored and/or distributed on a suitable medium, such as an optical storage medium or a solid state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. 
     However, the computer program may also be presented over a network like the World Wide Web and can be downloaded into the working memory of a data processor from such a network. According to a further exemplary embodiment of the present invention, a medium for making a computer program element available for downloading is provided, which computer program element is arranged to perform a method according to one of the previously described embodiments of the invention. 
     It has to be noted that embodiments of the invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method type claims whereas other embodiments are described with reference to the device type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters is considered to be disclosed with this application. However, all features can be combined providing synergetic effects that are more than the simple summation of the features. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof. 
     In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfil the functions of several items re-cited in the claims. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.