Abstract:
The present invention relates to a method and a device for determining a display mode for displaying at least two images of an object. The positions of the images and the display mode of the images are selected based on a comparison of a provided distance value between the edges of the two displayed images and a distance threshold value. By e.g. continuously varying the distance value, the corresponding images and display mode are adapted to the actual distance value.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method for displaying at least a first image and a second image of an object on a display, to a computer program for carrying out a method, and to a computer-readable medium on which a computer program is stored. Furthermore, the present invention relates to a device for calculating a display mode for displaying at least a first image and a second image of an object. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the medical domain of presenting medical images of multi-modality volume acquisitions, the medical images may be presented and analyzed as slabs. 
         [0003]    The document U.S. Pat. No. 8,208,483 B2 relates to a medical imaging system comprising one or more displays. Furthermore, a viewer device is described in said document, which viewer device generates an interactive user interface screen on the display and enables a user to simultaneously inspect selected image data of multiple patients or multiple images. 
         [0004]    US 2012/0069968 A1 discloses a method and apparatus for positioning a patient for radiation treatment. The method includes obtaining a plurality of projection images of a patient positioned on a treatment couch, displaying at least one of the plurality of projection images with a corresponding synthetic projection image on a display, adjusting the position of the at least one projection image on the display to approximately align with the corresponding synthetic projection image in response to a user dragging the at least one projection image on the display with a user interface device, and moving the treatment couch to position the patient based on position adjustments of the at least one projection image. 
         [0005]    US 2009/0238329 A1 discloses a method and device for medical imaging, a number of input parameters with regard to an image exposure are imported into a controller of the imaging device, that associate a desired image quality with a defined image exposure region. A number of control parameters are determined corresponding to each input parameter. The controller supplies each control parameter to the image acquision apparatus for accquiring the image exposure of the examination region with desired local image quality. 
       SUMMARY OF THE INVENTION 
       [0006]    It may be seen as an object of the present invention to enable an improved analysis and/or an improved displaying of medical images. 
         [0007]    This object and further objects are achieved by the subject-matter of the independent claims. Further embodiments and advantages are set out in the respective dependent claims. 
         [0008]    The described embodiments similarly pertain to the method, the computer program, the computer-readable medium, and the device, although specific embodiments may be explained in detail in the following with respect to a method or a device only. Synergetic effects may arise from different combinations of the embodiments although they might not be described in detail hereinafter. 
         [0009]    According to an exemplary embodiment of the invention, a method for displaying at least a first image and a second image of an object on a display is presented. Said method comprises the steps of providing a distance value between an edge of the first image and an edge of the second image of the object. Moreover, the method comprises the step of displaying a side by side view of the first image and the second image on the display in case the provided distance value exceeds a distance threshold value, wherein a distance between the edge of the displayed first image and the edge of the displayed second image corresponds to the provided distance value; or displaying an overlay view of the first image and the second image in case the provided distance value is less than the distance threshold value. 
         [0010]    If desired, the method may comprise the steps of providing the first image representing a first volume of the object and providing the second image representing a second volume of the object. 
         [0011]    Hereinafter, the first image and the second image may refer to two distinct images. Furthermore, the first image and the second image may also refer to a combination of the first image and the second image. Thus, the overlay view should also be understood as a displaying of the first image and the second image. 
         [0012]    Thus, it may be seen as an aspect of the invention to provide for a method for controlling the image display of medical images. A further aspect of the invention is to provide for a method, which is supported by a computer implemented user interface, to react to a user input defining a distance value between displayed images and to display a combination of two images based on said distance value. In other words, the method provides for an automated adaption of two different displaying modes of two images, which images may represent one or more volumes of the object. For example, such an automated adaption can be performed by calculating which display mode shall be used on the basis of a predetermined threshold value and an actually determined or an actually provided distance value. Therein the two modes of displaying are a side by side view and an overlay view. 
         [0013]    The object, images of which are used by the present invention, may refer to any object from which medical images can be displayed. For example, the object may refer to a human body, an animal body, or a medical sample. 
         [0014]    The first image may be an image representing a first volume of the object and the second image may be an image representing a second volume of the object. Hereinafter, the first volume and the second volume of the object may refer to the same volume of the object. For example, the first volume and the second volume refer to the same volume at different points in time. Moreover, the first volume and the second volume may refer to different volumes. 
         [0015]    The volume of the object may refer to a partial volume of the object. For example, the volume is a slab. A slab may refer to a thick slice of the object and may be defined in terms of a position and an orientation of a plane and a thickness. In order to display the slab, the slab may be rendered on a display and may be resampled using a model-view-projection transformation and a selected rendering function. The slab on the display may be presented orthogonal to the viewing direction. This will become apparent from and elucidated with the following detailed explanations. For example, a slab is a combination of multiple slices. The method step of providing a distance value may refer to the step of receiving a distance value. For example, the distance value may be provided by a distance value input device. In particular, the distance value input device may be embodied as a keyboard, a mouse, a graphical representation of a button, or as a microphone. In case the distance value input device is a microphone, the distance value may be provided acoustically such that the distance value may be provided without having to handle an input device. 
         [0016]      FIG. 1  shows an object used in accordance with an exemplary embodiment of the present invention, which object comprises a first volume and a second volume. In  FIG. 2 , a flow diagram for a method for displaying at least a first image and a second image of an object is shown.  FIG. 3  shows an exemplary embodiment assembly comprising a device for carrying out the herein presented method. 
         [0017]    The first and second image may refer to first and second image data. For example, the data can be stored in and provided by a database. The present invention may make use of a communication between the device of the present invention and the data base to submit desired and or necessary data, like e.g. image data. Thus, the step of providing the first image and the second image may refer to the step of providing first image data and second image data. The first and second image data may thus be sent to a displaying device, for example, a screen. The first and second image may each comprise a plurality of voxels, i.e. a plurality of 3 dimensional picture elements. However, also other image data formats may be used. For example, 2 dimensional data may be used in addition or alternatively. 
         [0018]    The steps of displaying the first image and the second image may thus refer to or may be seen as sending first image data and second image data to a displaying device and/or to calculating a screen image comprising the first image and the second image based on first image data and second image data. The side by side view may refer to a displayed image where the first image is located next to the second image. In other words, the first image and the second image are presented in different regions of the display. They may be displayed adjacent from each other with an adjustable separation range. However, in the overlay view, the first image may be presented over the second image or vice versa. Furthermore, the first image and the second image may be combined such that both features of the first image and of the second image are visible in the overlay view. In other words, the overlay view may comprise a superposition of the first image and the second image. 
         [0019]    The first volume and the second volume may be registrated in a same frame of reference, e.g. a patient coordinate space in, for example, millimeters. During the displaying of the volumes comparable slices of the volumes can be resampled based on a definition of the volumes and the orientation of the resampling planes. For example, the sampling planes through the volumes are aligned orthogonal to the caudal-cranial direction, i.e. the feet to head direction. The step of providing the distance value between an edge of the first image representing the first volume and an edge of the second image representing the second volume of the object can be carried out, for example, by a distance value input device. Such a distance value input device may be initialized at a starting position, which may represent a distance value which is larger than the distance threshold value. However, also other initializations can be used without departing from the present invention. 
         [0020]    The method according to the present invention may facilitate to interactively browse, zoom and rotate through the images. The sizes of the rendered images may change depending on the orientation, the zoom-factor and the position of the volumes. By changing the distance value between the images, the presentations may be lined-up more closely. While browsing through the images, a side by side view may offer maximum contrast and/or brightness resolution and/or an optimal coherent global impression of the individual images. Furthermore, an overlay view may offer a clearer distinctive view on local image differences. 
         [0021]    The distance threshold value may define a threshold value which defines a transition between the side by side view and the overlay view. 
         [0022]    According an exemplary embodiment of the present invention, the provided distance value is compared with the distance threshold value and a side by side view or an overlay view is displayed based on said comparison. For example, the distance threshold value can be equal to zero. If the distance threshold value is zero, the overlay mode is activated when the first image and the second image fully overlap. However, also other values different from zero can be used. Thus, the overlay view may be activated when the first image and the second image partially overlap. The distance threshold value may be stored in the database or may also be received as an input from the user and can be processed accordingly. 
         [0023]    The displaying of the first image and the second image based on a comparison of the provided distance value and the distance threshold value may alternatively be provided by the steps of displaying a side by side view of the first image and the second image on the display in case the provided distance value is larger than a distance threshold value; and displaying an overlay view of the first image and the second image in case the provided distance value is less than the distance threshold value. The user may also select which display mode he prefers in case the provided distance value is equal to the threshold value of the distance. Both options, the side by side view and the overly view can be used in case the provided distance value is equal to the threshold value of the distance. 
         [0024]    The present invention may thus overcome problems which arise when using the side by side view or the overlay view of multiple images separately. On the one hand, a drawback of only using the side by side view may be that detailed voxel-level comparison could be difficult. On the other hand, the overlay view may be sensible to image mismatches, motion artifacts, and to image lost due to a lack of contrast. Thus by combining the side by side view and the overlay view of multiple images on the basis of the provision of a distance value, the problems of the side by side view may be overcome by the overlay view and vice versa. 
         [0025]    Therefore, the previously described method may be seen as a method in which a distance value is determined and in which a first image and a second image of a respective first and second volume of the object are provided. Furthermore, the displaying of a side by side view of the first image and the second image is comprised in case the distance value is larger than a threshold value. Alternatively, an overlay view of the first image and the second image is displayed by the presented method in case the distance value is less than a threshold value. If desired, the first image and the second image may be selected such that the distance between the displayed first image and the displayed second image is closest to the determined distance value. 
         [0026]    According to yet another exemplary embodiment of the invention, the first image is obtained with the method selected from the group comprising three-dimensional or rotational angiography, XperCT, X-ray computed tomography, magnetic resonance tomography, positron emission tomography, and any combination thereof; and the second image is obtained with the method selected from the group comprising three-dimensional rotational angiography, XperCT, X-ray computed tomography, magnetic resonance tomography, positron emission tomography, and any combination thereof. 
         [0027]    In other words, the method provides a displaying of comparable multi-modality images, which may be retrieved from a database based on a patient&#39;s identification data. The respective generation of such images may be part of a further exemplary embodiment of the presented method. 
         [0028]    According to a further embodiment of the present invention, the first image is obtained with a different imaging method than the second image. 
         [0029]    According to another exemplary embodiment of the present invention, the method further comprises the steps of rendering the first image using maximum intensity projection or multiplanar rendering and rendering the second image using maximum/minimum intensity projection or multiplanar average rendering. 
         [0030]    According to a further exemplary embodiment of the present invention, the method further comprises the steps of rendering the first image with a first transfer function; and rendering the second image with a second transfer function. The first transfer function may be coupled to the second transfer function in case the provided distance value is less than the distance threshold value. 
         [0031]    The transfer function, also known as window-width/level function, e.g., maps voxel densities to color/grey values. It may provide an interactive way to zoom-in on a limited range of voxel densities. In this way, an optimal view by concentrating on typical voxel densities, like bony versus soft tissue information may be provided. Furthermore, the transfer function may offer a way to focus on certain image feature like tumors in organs or to follow the up-take of small amounts of embolization materials like radiopaque contrasts agents or imageable beads during embolotherapy. 
         [0032]    According to a further exemplary embodiment of the present invention, the method further comprises the steps of continuously amending the distance value by means of a distance value determining device and continuously adapting the displaying of the first image and the second image simultaneously to the continuous amendment based on the distance value, respectively. 
         [0033]    The step of continuously amending the distance value by means of a distance value determining device may be performed by means of a sliding tool, which sliding tool is, for example, shown on the display device. Said sliding tool may be operated by means of a pointing device, for example, a mouse. Of course, other embodiments of the distance value determining device are possible. 
         [0034]    Thus, an aspect of the present invention is to provide an automatic method of providing a displayed image based on a continuous amendment of the distance value. The method comprises at least two different display modes, which are displayed based on the relation between the provided or determined distance value and the distance threshold value. When the distance value is amended by means of the distance value determining device, the displaying of the first image and the second image may be adapted such that the displayed first image and the displayed second image have a distance that essentially corresponds to the amended and/or actual distance value set by or by means of the distance value determining device. 
         [0035]    According to another exemplary embodiment of the invention, the first image and the second image are represented in different regions of the display in the side by side view. Furthermore, in the overlay view, the first image and the second image are combined and represented in the same region of the display. This will become more apparent from the description of the figures. 
         [0036]    According to a further exemplary embodiment of the invention, the method further comprises the step of adding a first color information and/or a first brightness information of the first image to a second color information and/or a second brightness information of the second image in case the provided distance value is less or equal to the distance threshold value. 
         [0037]    The first image may comprise at least a first value representing a color information and/or a first intensity value representing a first intensity information. For example, each pixel of the first image comprises an RGB triplet (R, G, B) comprising color information of the respective pixel and an alpha value, which comprises the opacity information. Equally, each pixel of the second image may comprise an RGB triplet as well as an alpha value. The combination of the first image and the second image in the overlay view may be achieved by adding the RGB triplets of each overlaying pixel of the first image and the second image. 
         [0038]    In the overlay view, the images may be displayed on top of each other making use of the additive characteristics of the RGB pixel values. In this way, overlapping contrasted image features will contain both colors while distinct features will maintain their original colors. The combination of the images may be independent of their overlapping order. 
         [0039]    According to another exemplary embodiment of the invention, the method further comprises the steps of providing a volume of interest of the object by means of volume metadata, selecting a first volume from the volume of interest, and selecting a second volume from the volume of interest. 
         [0040]    In other words, a volume of interest of the object, which is to be analyzed, may be selected. Said volume of interest may comprise the first volume as well as the second volume. The first volume and the second volume may refer to the same volume. Moreover, the first volume and the second volume may refer to the same volume at different points in time. For example, the first volume and the second volume are parallel slabs of the volume of interest. 
         [0041]    According to a further exemplary embodiment of the invention, a superposition of the first image and the second image is displayed in the overlay view. Furthermore, in the overlay view, the first image is rendered with a first color and the second image is rendered with a second color and the first color is different than the second color. 
         [0042]    In other words, the first image is colored with a first color and the second image is colored with a second, different color. Thus, in the overlay view, features of the first image are visible in the first color and features of the second image are visible in the second color. Furthermore, features that are the same in the first image and the second image are shown in a third color, wherein the third color is a mixture of the first color and the second color. Thus, it is possible to assign the features to the first image and/or to the second image. Furthermore, it is also possible to identify the differentiating features between the first image and the second image as well as to identify equal features of the first image and the second image. 
         [0043]    According to another exemplary embodiment of the invention, the first color is complementary to the second color. 
         [0044]    In other words, the first color and the second color are defined such that a mixture of the first color and the second color will result in white. Thus, in the overlay view, features of the first image that are equal to features of the second image may be displayed in white. For example, the first color is red, the second color is cyan, and the combination of the first color and the second color is white. 
         [0045]    According to another embodiment of the invention, the method further comprises the steps of providing a second distance value between an edge of the second image and an edge of a third image of the object. The method further defines a step of displaying a side by side view of the second image and the third image on the display in case the provided second distance value exceeds a second distance threshold value, wherein a distance between the edge of the displayed second image and the edge of the displayed third image corresponds to the provided second distance value. Furthermore, the method comprises the steps of displaying an overlay view of the second image and the third image in case the provided second distance value is less than the second distance threshold value; or displaying an overlay view of the first image, the second image, and the third image in case the provided first distance value is less than the first distance threshold value and the provided second distance value is less or equal to the second distance threshold value. Moreover, the method may comprise the step of providing a third image representing a third volume of the object. 
         [0046]    The user may also select which display mode he prefers in case the provided distance value is equal to the threshold value of the distance. Both options, the side by side view and the overlay view can be used in case any of the provided distance values is equal to the respective threshold value. 
         [0047]    Thus, the method provides a first image representing a first volume, a second image representing a second volume, and a third image representing a third volume of the object. Therein the first distance between an edge of the first image and an edge of the second image as well as the second distance between an edge of the second image and an edge of the third image of the object is configurable and/or adjustable for the user. Corresponding adjustment means, like a first and a second distance value determining device can be provided by the present invention. In other words, first the first distance value and the second distance value are provided and then the first image, the second image, and the third image are displayed based on the first distance value and the second distance value. As has been described before, a corresponding comparison between the received or determined distance value and the associated/ corresponding distance threshold value can be carried out, i.e. calculated, according to the present invention. 
         [0048]    Thus, an extension and generalization of the method for or to three images of an object is presented. 
         [0049]    By using a plurality of volumes typical image attributes, which are optimally presented by one imaging modality such as MR or PET, may be combined with image attributes like high resolution anatomical details represented or available by images of another modality such as pre-interventional (Xper)-CT, in combination with interventional XperCT image data showing interventional materials, like ablation needles, imageable beats, stents etc. 
         [0050]    Apparently, the herein presented systematic of the method of the present invention can also be applied in an analogue way to four, five and even more images of the desired object. 
         [0051]    According to an exemplary embodiment of the invention, a computer program element for displaying at least a first image and a second image of an object on a display is presented, which computer program element, when being executed by a processor, is adapted to carry out any of the above-defined methods. 
         [0052]    The computer program element may be part of a computer program, but it can also be an entire program by itself. For example the computer program element may be used to update an already existing computer program to get to the present invention. 
         [0053]    According to another exemplary embodiment of the invention, a computer-readable medium on which a computer program element is stored, wherein the computer program element enables a processor to carry out any of the above-defined methods, is presented. 
         [0054]    The computer readable medium may be seen as a storage medium, such as for example, a USB stick, a CD, a DVD, a data storage device, a hard disk, or any other medium on which a program element as described above can be stored. 
         [0055]    According to another exemplary embodiment of the invention, a device for calculating a display mode for displaying at least a first image and a second image of an object is presented, wherein the device comprises a processor. Furthermore, the device is configured to receive data of a distance value between an edge of the first image and an edge of the second image of the object. In case the distance value exceeds a distance threshold value, the processor is configured to generate a first display signal comprising information of a side by side view of the first image and the second image, wherein a distance between the edge of the displayed first image and the edge of the displayed second image corresponds to the provided distance value. In case the distance value is less than the distance threshold value, the processor is configured such that a second display signal is generated comprising information of an overlay view of the first image and the second image. 
         [0056]    For example, in  FIG. 3 , an exemplary assembly comprising a device for calculating a display mode for displaying at least a first image and a second image of an object is shown. 
         [0057]    In general, the data of the distance value between an edge of the first image and an edge of the second image may be a number defining said distance between the edge of the displayed first image and the edge of the displayed second image. Furthermore, the data of the distance value may also refer to a coordinate or a set of coordinates in order to control a distance value input device, for example, a sliding element on a display, which can be controlled by means of, e.g., a mouse. 
         [0058]    The selection step of a first or second image performed by the processor may refer to a database query such that the first image and the second image can be retrieved from the database. 
         [0059]    A first display signal may enable and/or cause a display device to show an image on a screen with a side by side view of the first image and the second image. In other words, the first image and the second image are located in different regions of the screen image. Equally, the second display signal enables and/or causes the display to show a screen image with an overlay view of the first image and the second image. Thus, in the overlay view, the screen image may comprise a superposition of the first image and the second image. 
         [0060]    Therefore, a control loop of the display is presented based on the input regarding the distance between the edge of the first image and the edge of the second image and based on the distance threshold value. 
         [0061]    According to another exemplary embodiment of the invention, the device further comprises a display device configured to display the first display signal and the second display signal; and a distance value determining device configured determine the distance value and to create the corresponding data of the distance value. 
         [0062]    The display device may refer to a computer display, a display of a mobile device, or to an image which is projected by a beamer. Moreover, the display device may refer to a touch screen such that, e.g., the display device and the distance value determining device are incorporated by the same device. The distance value determining device may refer to the usual input devices such as a keyboard or a mouse. Furthermore, the distance value determining device may also refer to a microphone such that the distance value may be provided during an operation or examination. 
         [0063]    The gist of the invention may be seen in providing for an automatic method for displaying images of an object. By providing a distance value between a displayed first image and a displayed second image, a displaying mode of the first image and the second image is determined. Thus, by controlling and/or selecting the distance value and/or the distance threshold value, the display mode is automatically selected. This may improve the image analysis for the medical practitioner. 
         [0064]    It has to be noted that the embodiments of the invention are described with reference to the different subject-matters. In particular, some embodiments are described with reference to device type claims whereas other embodiments are described with reference to method type claims. However, a person skilled in the art will gather from the above and the following description that unless other notified in addition to any combination of features belonging to one type of subject-matter, also any combination between features relating to different subject-matter is considered to be disclosed with this application. 
         [0065]    The aspects described above and further aspects, features and advantages of the invention may also be found in the example embodiments which are described in the following with reference to the appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0066]    Exemplary embodiments of the invention will be described in the following drawings. Any reference signs in the claims should not be construed as limiting the scope of the claims. 
           [0067]      FIG. 1  is a schematic drawing of a human body which can be used for understanding the present invention. 
           [0068]      FIG. 2  shows a flow-chart according to an exemplary embodiment of the present invention. 
           [0069]      FIG. 3  shows a schematic drawing of a device according to an exemplary embodiment of the present invention. 
           [0070]      FIG. 4  shows a schematic drawing of a display view according to an exemplary embodiment of the present invention. 
           [0071]      FIG. 5  shows a schematic drawing of a display view according to an exemplary embodiment of the present invention. 
           [0072]      FIG. 6  shows a schematic drawing of a display view according to an exemplary embodiment of the present invention. 
           [0073]      FIG. 7  shows a schematic drawing of a display view according to an exemplary embodiment of the present invention. 
           [0074]      FIG. 8  shows a schematic drawing of a display view according to an exemplary embodiment of the present invention. 
           [0075]      FIG. 9  shows a schematic drawing of a display view according to an exemplary embodiment of the present invention. 
           [0076]      FIG. 10  shows a schematic drawing of a display view according to an exemplary embodiment of the present invention. 
           [0077]      FIG. 11  shows a schematic drawing of a display view according to an exemplary embodiment of the present invention. 
           [0078]      FIG. 12  shows a schematic drawing of a display view according to an exemplary embodiment of the present invention. 
           [0079]      FIG. 13  shows a schematic drawing of a display view according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0080]      FIG. 1  shows a contour of a human body  101  comprising a volume of interest  102  that can be used in accordance with an exemplary embodiment of the present invention. The volume of interest  102  comprises a first volume  103  and a second volume  104 . A first image and second image may be taken from the first volume  103 . Alternatively, the first image may be rendered on the basis of the first volume  103  and the second image may be rendered on the basis of the second volume  104 . The first volume  103  has a thickness  106 . The region of interest or volume of interest  102  may represent a part of the body  101  which is scanned by means of an imaging method. Exemplarily, the imaging method may be selected from the group comprising three-dimensional rotational angiography, XperCT, X-ray computed tomographic, magnetic resonance tomography, positron emission tomography, and any combination thereof.  FIG. 2  shows a flow-chart for a method for displaying at least a first image and a second image of an object on a display. The method comprises the steps of providing a distance value between an edge of the first image and an edge of the second image of the object which step is shown with reference sign  201 . Moreover, providing a first image representing a first volume of the object is depicted with  202  and providing a second image representing a second volume of the object with  203 . Displaying a side by side view of the first image and the second image on the display in case the provided distance value exceeds a distance threshold value, wherein a distance between the edge of the displayed first image and the edge of the displayed second image corresponds to the provided distance value, is shown with step  204 . Alternatively, displaying an overlay view of the first image and the second image in case the provided distance value is less than the distance threshold value is carried out in step  205 . The first volume and the second volume may describe the same or different volumes of the object. Moreover, the first volume and the second volume may relate to the same volume of the object scanned at different points in time. 
         [0081]    Steps  202  and  203  shall not be construed as being essential. In other words, also a method comprising only the steps  201 ,  204 , and  205  is herewith disclosed, as has been described before in the context of an exemplary embodiment and is described in the claims. The method steps  201 ,  202  and  203  may be performed in the order shown in  FIG. 2 . The method steps  202  and  203  may also be performed at the same time, i.e. in parallel to each other. Furthermore, the method steps may also be performed in a different order. The method of  FIG. 2  may be seen as a method for controlling the image display of medical images based on the actually given and desired distance value. 
         [0082]      FIG. 3  shows a schematic drawing of an assembly for calculating and for displaying a display mode of at least a first image and a second image of an object according to an exemplary embodiment of the invention. The assembly  301  comprises a device  302  for calculating a display mode for displaying at least the first image and a second image of an object  101  and comprises a processor  303  which performs or controls the method steps. For carrying out the method which is, for example, described with reference to  FIG. 2 , the device  302  is configured to receive data  308  of a distance value between an edge of the first image and an edge of the second image. Furthermore, the device  302  may be configured to receive data  309  of a distance threshold value and/or data  310  defining a region of interest  102  of the object  101 . Furthermore, the device  302  is configured to receive image data for the first image and the second image from a database  311 . In case the distance value exceeds a distance threshold value, the processor  303  is configured to generate a first display signal  312  comprising information of a side by side view  327  of the first image and the second image. In case the distance value is less than the distance threshold value, the processor  303  is configured to generate a second display signal  313  comprising information of an overlay view  328  of the first image and the second image. The device  302  may be connected to a display  304  and/or  305 .  FIG. 3  may also be understood such that only one display is used and  304  and  305  depict different situations of one single display. There is also a feedback signal provided from the display or displays  304  and  305  to the device  302  regarding the distance value. However, this signal feedback is not shown in  FIG. 3 . Furthermore, the device  302  may be connected to input devices such as a mouse  307  and/or a keyboard  306 . In the exemplary embodiments shown hereinafter, the distance threshold value is exemplarily set as being equal to zero. However, this has not to be seen to restrict the distance threshold value to zero in general. The same functionality is achievable for a distance threshold value being non equal to zero. The first display signal  312  comprises data, which, when sent to a display device  304 , enables and/or cause the display device  304  to show a displayed image  327 , which is a side by side view. For example a user interface with a toolbar  314  may be comprised. The toolbar  314  comprises a first sliding tool  315  for controlling the distance value and a second sliding tool  316  for controlling the thickness of the slab and/or the volumes. Said first and second sliding tools  315  and  316  may be operated with the mouse  307 . In the displayed image  327  it is shown that the sliding tool  315  indicating the distance value is configured to a value larger than zero, i.e. larger than the distance threshold value. Consequently, a first image  317  and a second image  318  are shown in a side by side view. The first image  317  comprises an exemplary and symbolic first feature  320  and a second image  318  comprises an exemplary and symbolic second feature  319 . 
         [0083]    The second display signal  313  comprises data, which, when sent to a display device  305 , enables and/or cause the display device  305  to show a displayed image  328 , which is an overlay view. For example, a user interface with a toolbar  321  is comprised. The toolbar  321  comprises a first sliding tool  322  for controlling the distance value and a second sliding tool  323  for controlling the thickness of the slab. In the displayed image  328 , the first sliding element  322  indicates that the provided distance value is equal to zero. Consequently, an overlay view of the first image and the second image is shown. Thus, it becomes clear that signal is sent from the displays  304  and  305  to the device  302  regarding the respective distance value. The overlay view comprises a superposition  324  of the first image and the second image. The superposition  324  comprises the feature of the first image  325  and the feature of the second image  326 . For example, the first feature  325  is shown with a different characteristic as the second feature  326 . For example, the first feature  325  is shown as a straight line and the second feature  326  is shown as dashed line. The different characteristics may also be different colors. For example, the first feature  325  may be displayed in a first color, e.g., in red and the second feature  326  may be displayed in a second color, e.g., in blue. In the exemplary embodiments shown hereinafter, exemplary features are shown as hatched regions. Different hatched regions may also refer to regions with different colors and/or brightness. Cross hatched regions may refer to regions comprising a mixture of two colors. 
         [0084]      FIG. 4  shows a schematic display view  401  according to an exemplary embodiment of the present invention. In particular, a side by side view of the first image  433  and the second image  434  is shown. The display view  401  comprises a controlling section  402  and an image displaying section  403 . The controlling section comprises a first sliding tool  404  for controlling the distance value between an edge of the first image and an edge of the second image, wherein the first image and the second image are images of a slab. A second sliding tool  405  is configured to control the thickness of the slab. Furthermore, the thickness of the slab may be configured by means of an input field  406  where the slab thickness may be entered in terms of a number. Furthermore, the controlling section  402  comprises multiple buttons, which may be provided in various different combination representing different corresponding embodiments. Thus,  FIG. 4  shall not be construed such that all buttons and functions are essential for the working principle of the underlying embodiment. In the following, a short description of the different buttons as well as of the associated functions is given. The button  407  may be selected to choose the patient out of the patient database, whose images shall be displayed. The button  408  may be selected to print the images. With the button  409 , the image data may be exported for being imported in other programs. Buttons  410  to  416  will offer different tools available to the practitioner. Button  410  starts the histogram function, button  411  the XperCT function, button  412  the EmboGuide function, button  413  the New function that allows zoomed reconstruction, button  414  the 3D Roadmap function, button  415  the Assess 3D function, button  416  the Analysis function and button  417  the XperGuide function. In the field  418 , the transfer function  419  and the line  420  are shown. In the dropdown selection field  421  it is indicated that the same transfer function shall be used for both images. With the dropdown field  422 , the transfer function can be selected. Button  423  may be selected to start the Measurement function, button  424  to start the Movie function, and button  425  to start the Dual View function. Button  426  may be selected to start the Overlay function, button  427  the Register function, button  428  the Remask function, button  429  the Select Set function, button  430  the Remask function, and button  431  the Fullscreen function. In the field  432 , a schematic illustration of the orientation of the imaging device is shown. In the present exemplary embodiment, the functions XperCT and Overlay are selected. 
         [0085]    The Overlay function may select the last used (right-side) secondary volume together with belonging registration and transfer function information. The Registration function may start the registration dialog for the manual and/or automatic 3D-3D registration. The Remask function may allow the selection of the overlay volume from a set of available secondary volumes. By means of the Select Set function matching volumes such as PET volumes, or derived/processed volumes acquired in the same frame of reference as the current selected secondary volume, can be selected re-using the registration information. The Fullscreen function may represent the image information in full-screen mode as shown in  FIG. 6 , getting rid of the graphic dialogs. 
         [0086]    The image display section  403  comprises a first tab  435  for displaying a first overlay, a second tab  436  for displaying a second overlay, and a third tab  437  for displaying a third overlay. In the present exemplary embodiment the first tab  435  showing the first overlay is selected. Furthermore, a first image  433  and a second image  434  are shown. The first image  433  and the second image  434  may represent a first volume  103  of the object  101 . The orientation of the volume  103  in the object  101  may be changed by means of the first rotation button  438 , the second rotation button  439 , the third rotation button  440 , and the fourth rotation button  441 . The actual orientation of the first volume  103  with respect to the object  101  is shown by means of the graphical illustration  442 . In other words, the graphical illustration  442  shows the viewing direction. In the displayed image  401 , a configuration is shown where the sliding tool  404  shows a distance value, which is greater than zero, i.e. greater than the threshold value. 
         [0087]    In  FIG. 5 , a displayed image  501  according to an exemplary embodiment of the invention is shown, wherein, in the overlay view, a superposition of the first image and the second image is displayed. Exemplarily the first image is rendered with a first color and the second image is rendered with a second color, and wherein the first color is different than the second color. In the controlling section, the button  411  for the function XperCT is selected. Furthermore, the button  426  for the Overlay function is selected. The second sliding element  405  for the slab thickness is configured to a slab thickness of 2.99 mm, which value is shown in the text field  406 . The first sliding element  404  shows that the distance value between an edge of the first image and an edge of the second image is equal to zero, i.e. less or equal to the distance threshold value. Since the distance value between the edge of the first image and the edge of the second image of the object  101  is equal to zero and therefore less or equal to the distance threshold value, an overlay view of the first image and the second image is shown in the image displaying section. The overlay view is a superposition  505  of the first image and the second image. In the superposition  505 , features  506  of the first image are shown with a first characteristic, for example, with a hatching in a first direction. Features  507  of the second image are shown with a second characteristic, for example, with a hatching in a second direction. Furthermore, features  508  which are the same in the first image and in the second image are shown with the first characteristic and with the second characteristic. For example, the feature  508  is shown with a cross hatching. The different hatching in the first direction may refer to a first color and the hatching in the second direction may refer to a second color. The cross hatching may refer to a mixture of the first color and the second color. Thus, in the overlay view, the different features can be identified and assigned to the first image and/or to the second image. Furthermore, it may be identified, which features are different in the first image and in the second image and which features are the same in the first image and in the second image. 
         [0088]      FIG. 6  shows a displayed image  601  of a full screen view according to an exemplary embodiment of the invention. The displayed image  601  shows a side by side view of a first image  602  and a second image  603  based on a given combination of a desired distance between an edge of the displayed first image  602  and an edge of the displayed second image  603  and a given threshold value for the distance. The first image  602  comprises features  605 ,  607 , and  609 . The second image  603  comprises the features  606  and  608 . The feature  605  is only visible in the first image  602 . Furthermore, it is visible that the feature  607  and the feature  606  differ from each other since there is a distance between the first volume  103  and the second volume  104 . Equally, the features  609  and  608  differ from each other. With the button  604 , the full screen view can be quit. With the buttons  438 ,  439 ,  440 , and  441 , the orientation of the first volume  103  in the object  101  can be changed. The actual orientation of the first volume  103  with respect to the object  101  is shown in the graphical illustration  442 . 
         [0089]      FIG. 7  shows a displayed image  701  of a full screen view according to an exemplary embodiment of the invention. The full screen view comprises a first image  702  with features  704  and  705 . A second image  703  with a feature  706  is shown. With the button  438 ,  439 ,  440 , and  441 , the orientation of the first volume  103  in the object  101  can be changed. In the field  704 , the orientation of the first volume  103  with respect to the object  101  is shown. With the button  604 , the full screen view can be quit. 
         [0090]      FIG. 8  shows a displayed image  801  of a full screen view according to an exemplary embodiment of the invention. The full screen view shows a first image  802  and a second image  803 , wherein the first image  802  is recorded using a different imaging method than the second image  803 . In the second image  803 , further features  804  and  805  are visible. 
         [0091]      FIG. 9  shows a displayed image  901  according to an exemplary embodiment of the invention. The button  411  shows that the XperCT function is selected. The dropdown field  421  indicates that the overlay mode for the transfer functions is selected. Furthermore, the button  426  indicates that the Overlay function is selected and the button  429  indicates that the Select Set function is selected. With the second sliding element  405 , a slab thickness of 0.98 mm is configured, which is also shown in the text field  406 . With the first sliding element  404 , a distance value equal to zero is selected, i.e. less or equal to the distance threshold value. Since the distance value is equal to zero and therefore less or equal to the distance threshold value, an overlay view  902  of the first image and the second image is shown. In the overlay view, features  903  belonging to the first image are shown with a first characteristic, for example, a hatching in a first direction. Features  904  belonging to the second image are shown with a second characteristic, for example, with a hatching in a second direction. Features, which are the same in the first image and the second image, are shown with both characteristics, for example, with a cross hatching. As defined above, the different hatchings may refer to different colors. 
         [0092]    In  FIG. 10 , a displayed view  1001  according to an exemplary embodiment of the invention is shown. With the button  412 , the EmboGuide function is selected. Furthermore, the controlling section comprises the button  1003  for selecting the Dual View function, button  1004  for selecting the Lesion 3D function, button  1005  for selecting the Embo Plan function, and button  1006  for selecting the Embo Live function. With button  426 , the Overlay function is selected. The sliding element  405  indicates that a slab thickness of 89.98 mm is selected, which thickness is also displaced in the text field  406 . With the first sliding tool  404 , a distance value between an edge of the displayed first image and an edge of the displayed second image is selected, which distance value is greater than zero, i.e. greater than the distance threshold value. 
         [0093]    The functions Dual-View, Lesion-3D, Embo-Plan and Embo-Live may provide the procedure steps that are part of the so called EmboGuide tool. The EmboGuide tool offers support for arterial embolization procedures. The dual view procedure is supporting the diagnostic step based on multi-modality information comparable to the previously described XperCT-Dual View function. The Lesion3D function may be used to semi-automatically segment lesions in 3D. The Embo-plan function may be used for automatically feeder detection and indicates the vessel paths towards the selected lesions. The Embo-Live step may support the interventional navigation by overlaying live real-time 2D fluoro on the 3D-volume and planning information. 
         [0094]    In the image display section, an overlay view of the first image and the second image is shown. In this exemplary embodiment, the distance threshold value is larger than zero. The provided distance value selected with the first sliding tool  404  is less or equal to the distance threshold value. Consequently, an overlay view with a superposition  1002  of the first image and the second image is shown. Features  1007  of the first image are shown with a first characteristic, for example, with a hatching in a first direction. Features  1008  belonging to the second image are shown with the second characteristic, for example, with a hatching in a second direction. Features  1009 , which are the same in the first image and in the second image, are shown with the first characteristic and the second characteristic, for example, with a cross hatching. 
         [0095]    In  FIGS. 11, 12, and 13 , a displayed image for displaying three images of an object is shown. Thus, the displayed images  1101 ,  1201 , and  1301  shown in  FIGS. 11, 12, and 13  may be a result of a method for displaying at least a first image, a second image, and a third image of an object on a display, which method comprises the steps of providing a first distance value between an edge of the first image and an edge of the second image of the object, providing a second distance value between an edge of the second image and an edge of the third image of the object. Furthermore, the method comprises the steps of displaying a side by side view of the first image and the second image on the display in case the provided first distance value exceeds a first distance threshold value wherein a distance between the displayed first image and the displayed second image corresponds to the provided first distance value; displaying an overlay view of the first image and the second image in case the provided first distance value is less or equal to the first distance threshold value; displaying a side by side view of the second image and the third image on the display in case the provided second distance value exceeds a second distance threshold value, wherein a distance between the edge of the displayed second image and the edge of the displayed third image corresponds to the provided second distance value; displaying an overlay view of the second image and the third image in case the provided second distance value is less or equal to the second distance threshold value; or displaying an overlay view of the first image, the second image, and the third image in case the provided first distance value is less or equal to the first distance threshold value and the provided second distance value is less or equal to the second distance threshold value. Moreover, the method may comprise the steps of providing a first image representing a volume of the object, providing a second image representing the volume of the object, and providing a third image representing the volume of the object 
         [0096]    In the exemplary embodiments shown in  FIG. 11  to  FIG. 13 , the distance threshold value is equal to zero. Thus, when the provided distance value is equal to zero, an overlay view of the respective images is shown and, when the provided distance value is greater than zero, a side by side view is shown. Each of the user interfaces shown in the first displayed image  1101 , the second displayed image  1201 , and the third displayed image  1301  comprises a sliding tool  1102  for controlling the first distance value and a sliding tool  1103  for controlling the second distance value. 
         [0097]    In the display view  1101  shown in  FIG. 11 , the first sliding tool  1102  indicates that the first distance value is greater than zero and the second sliding tool  1103  indicates that the second distance value is greater than zero. Consequently, a side by side view of the first image  1104 , the second image  1105 , and the third image  1106  is shown, wherein a first distance between an edge of the displayed first image  1104  and an edge of the displayed second image  1105  corresponds to the first distance value, and wherein a second distance between an edge of the displayed second image  1105  and an edge of the displayed third image  1106  corresponds to the second distance value. The first image comprises a first feature  1107 , the second image  1105  comprises a second feature  1108 , and the third image  1106  comprises a third feature  1109 . 
         [0098]    In the display view  1201  shown in  FIG. 12 , the first sliding tool  1102  indicates that the first distance value is equal to zero and the second sliding tool  1103  indicates that the second distance value is greater than zero. Consequently, an overlay view  1202  of the first image and the second image is shown. The overlay view  1202  comprises the first feature  1107  of the first image with a first characteristic, for example, as a straight line and the second feature  1108  of the second image shown with a second characteristic, for example, as a dashed line. The third image  1106  is shown next to the superposition  1202  of the first image  1104  and the second image  1105 , wherein a distance between the displayed superposition  1202  and the displayed third image  1106  corresponds to the second distance value. 
         [0099]    In the displayed image  1301  shown in  FIG. 13 , the first sliding tool  1102  indicates that the first distance value is equal to zero and the second sliding tool  1103  indicates that the second distance value is equal to zero. Consequently, the superposition  1302  of the first image  1104 , the second image  1105 , and the third image  1106  is shown. The first feature  1107  belonging to the first volume  103  is shown with a first characteristic, for example, as a straight line, the second feature  1108  belonging to the second volume  104  is shown with a second characteristic, for example, as a dashed line, and the third feature  1109  belonging to the third volume is shown with a third characteristic, for example, as a dotted circle. 
         [0100]    Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, from the disclosure, and from the appended claims. 
         [0101]    In the claims, the word “comprising” does not exclude other elements or steps and the indefinite article “a” and/or “an” does not exclude a plurality. 
         [0102]    A single processor or other unit may fulfill the functions of several item recited in the claims. 
         [0103]    The mere fact that certain measures are recited in mutually different dependent claims does not indicate that the combination of these measures cannot be used to advantage. The reference numerals in the claims are not intended to restrict the scope of the claims. 
       LIST OF REFERENCE SIGNS 
       [0104]      101  object 
         [0105]      102  volume of interest 
         [0106]      103  first volume 
         [0107]      104  second volume 
         [0108]      106  thickness of the first volume 
         [0109]      201  providing a distance value 
         [0110]      202  providing a first image 
         [0111]      203  providing a second image 
         [0112]      204  displaying a side by side view 
         [0113]      205  displaying an overlay view 
         [0114]      301  assembly for calculating and displaying a display mode of at least a first volume and a second volume of an object 
         [0115]      302  device for calculating a display mode of at least a first volume and a second volume of an object 
         [0116]      303  processor 
         [0117]      304  display 
         [0118]      305  display 
         [0119]      306  keyboard 
         [0120]      307  mouse 
         [0121]      308  data of a distance value 
         [0122]      309  data of a distance threshold value 
         [0123]      310  data of a volume of interest 
         [0124]      311  database 
         [0125]      312  first display signal 
         [0126]      313  second display signal 
         [0127]      314  toolbar 
         [0128]      315  first sliding tool 
         [0129]      316  second sliding tool 
         [0130]      317  first image 
         [0131]      318  second image 
         [0132]      319  second feature 
         [0133]      320  first feature 
         [0134]      321  toolbar 
         [0135]      322  first sliding tool 
         [0136]      323  second sliding tool 
         [0137]      324  superposition image 
         [0138]      325  first feature 
         [0139]      326  second feature 
         [0140]      327  displayed image 
         [0141]      328  displayed image 
         [0142]      401  displayed image 
         [0143]      402  toolbar 
         [0144]      403  image displaying section 
         [0145]      404  first sliding tool 
         [0146]      405  second sliding tool 
         [0147]      406  input field 
         [0148]      407  Patients button 
         [0149]      408  Print button 
         [0150]      409  Export button 
         [0151]      410  Histogram button 
         [0152]      411  XperCT button 
         [0153]      412  EmboGuide button 
         [0154]      413  New button 
         [0155]      414  3D Roadmap button 
         [0156]      415  Assess 3D button 
         [0157]      416  Analysis button 
         [0158]      417  XperGuide button 
         [0159]      418  Transfer function field 
         [0160]      419  Transfer function graph 
         [0161]      420  intersecting line 
         [0162]      421  first Transfer function dropdown field 
         [0163]      422  second Transfer function dropdown field 
         [0164]      423  Measurement button 
         [0165]      424  Movie button 
         [0166]      425  Dual View button 
         [0167]      426  Overlay button 
         [0168]      427  Register button 
         [0169]      428  Remask button 
         [0170]      429  Select set button 
         [0171]      430  Remask button 
         [0172]      431  Full screen button 
         [0173]      432  imaging device illustration 
         [0174]      433  first image 
         [0175]      434  second image 
         [0176]      435  first tab for the first overlay 
         [0177]      436  second tab for the second overlay 
         [0178]      437  third tab for the third overlay 
         [0179]      438  first rotation button 
         [0180]      439  second rotation button 
         [0181]      440  third rotation button 
         [0182]      441  fourth rotation button 
         [0183]      442  orientation graphics 
         [0184]      501  displayed image 
         [0185]      505  superposition image 
         [0186]      506  feature 
         [0187]      507  feature 
         [0188]      508  feature 
         [0189]      601  displayed image 
         [0190]      602  first image 
         [0191]      603  second image 
         [0192]      604  exit button 
         [0193]      605  feature 
         [0194]      606  feature 
         [0195]      607  feature 
         [0196]      608  feature 
         [0197]      609  feature 
         [0198]      701  displayed image 
         [0199]      702  first image 
         [0200]      703  second image 
         [0201]      704  feature 
         [0202]      705  feature 
         [0203]      706  feature 
         [0204]      707  orientation graphics 
         [0205]      801  displayed image 
         [0206]      802  first image 
         [0207]      803  second image 
         [0208]      804  feature 
         [0209]      805  feature 
         [0210]      901  displayed image 
         [0211]      902  superposition image 
         [0212]      903  feature 
         [0213]      904  feature 
         [0214]      905  feature 
         [0215]      1001  displayed image 
         [0216]      1002  superposition image 
         [0217]      1003  Dual View button 
         [0218]      1004  Lesion 3D button 
         [0219]      1005  Embo-Plan button 
         [0220]      1006  Embo-Live button 
         [0221]      1007  feature 
         [0222]      1008  feature 
         [0223]      1009  feature 
         [0224]      1101  displayed image 
         [0225]      1102  sliding tool 
         [0226]      1103  sliding tool 
         [0227]      1104  first image 
         [0228]      1105  second image 
         [0229]      1106  third image 
         [0230]      1107  first feature 
         [0231]      1108  second feature 
         [0232]      1109  third feature 
         [0233]      1201  displayed image 
         [0234]      1202  superposition image 
         [0235]      1301  displayed image 
         [0236]      1302  superposition image