Abstract:
The invention relates to a system (100) for zooming an image displayed in a viewport, wherein the image comprises a plurality of regions, each region of the plurality of regions having a zoom function associated with the region, the system comprising an input unit (110) for receiving a region input for selecting a region of the plurality of regions and for receiving a zoom input for zooming the image, and a zoom unit (120) for zooming the image based on the zoom input, using the zoom function associated with the selected region. The zoom function associated with each region of the plurality of regions may be defined in any way deemed useful. For example, it may be defined in such a way that the selected region or an interesting portion of it is displayed in the viewport or, vice versa, the selected region or an interesting portion thereof is removed from the displayed view of the image. Advantageously, the user does not always need to precisely select the zoom center, as the application will select the zoom center, based at least on the selected region.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to displaying medical images. Especially, it relates to interactive zooming of images such as mammography images. 
       BACKGROUND OF THE INVENTION 
       [0002]    Currently, zooming of images is implemented by providing an input for changing the scale of the viewed area. Various implementations are possible. For example, in a 2D image, the user may select the zoom center (i.e., a fixed point in the 2D image) and scroll the mouse wheel to magnify or reduce the image. For mammography, this is typically combined by the display of mirrored images and mirrored pan and zoom operations as described in WO 2006/018816 entitled “Display system for the evaluation of mammographies”. Two-dimensional (2D) image zooming can be generalized to three-dimensional (3D) image zooming. For example, for perspective projection, the displayed images are zoomed when the camera moves along the line towards one of the vanishing points. For orthogonal projections, zooming is based on changing the scale in the planes perpendicular to the projection lines, i.e., perpendicular to the viewing direction. 
         [0003]    The drawback of available zoom implementations is that, when a user views an image region which is of interest to him, the zooming function does not always keep that region in the display. The region may quickly disappear from the display when the zoom center is fixed far away from the region of interest and the region of interest is close to the border of a viewport for displaying the image. This problem is often addressed by selecting the zoom center in the center of the region of interest. However, this method fails when the region of interest is adjacent to the border of the viewport. 
       SUMMARY OF THE INVENTION 
       [0004]    It would be advantageous to have an improved system for zooming images, wherein an image region of interest can be seen in the viewport while the image is zoomed-in. 
         [0005]    To achieve this, in an aspect, the invention provides a system for zooming an image displayed in a viewport, wherein the image comprises a plurality of regions, each region of the plurality of regions having a zoom function associated with the region, the system comprising:
       an input unit for receiving a region input for selecting a region of the plurality of regions and for receiving a zoom input for zooming the image; and   a zoom unit for zooming the image based on the zoom input, using the zoom function associated with the selected region.       
 
         [0008]    The zoom function associated with a first region of the plurality of regions, said first region surrounding the viewport center, may be defined, for example, in such a way that the center of the first region is the zoom center of a first zoom function associated with the first region. The zoom center of a second zoom function associated with a second region adjacent to the viewport border may be a point on the viewport border adjacent to the second region. 
         [0009]    A person skilled in the art will understand how to interpret the zoom center for 2-dimensional and 3-dimensional images. For example, in the case of 2-D images, the zoom center is a point in the image; in the case of orthogonal projection images, the zoom center is a point in the projection plane (viewing plane); for perspective images, the zoom center is the vanishing point. 
         [0010]    In an embodiment of the system, the selected region is defined on the basis of a viewport location comprised in the region input. Each region of the plurality of regions may be defined as a portion of the viewport. The viewport location means a location in the viewport. This location may be defined by a point or a pixel, for example. The selected region may be the region of the plurality of regions which comprises the viewport location comprised in the region input. 
         [0011]    In an embodiment of the system, the selected region is further defined based on an image object displayed in the viewport and the spatial relation between the viewport location and the object. This allows defining the selected region on the basis of the viewport as well as on the basis of the image contents. For example, a borderline of the region may be defined by a contour for delineating the object. 
         [0012]    In an embodiment, the system further comprises a segmentation unit for defining the image object. The segmentation may be carried out automatically, semi-automatically or manually. 
         [0013]    In an embodiment of the system, the zoom center of the zoom function associated with a region of the plurality of regions is at a predefined location within the region. For example, the zoom center may be the ‘mass’ center or ‘inertia’ center of the region. This helps to keep the portion of the displayed image comprising the center and its surroundings in the viewport. The skilled person will understand how to compute the mass or inertia center of a region replacing mass by image intensity. 
         [0014]    In an embodiment of the system, the zoom function associated with the region is a combination of a zoom, pan and/or rotation transformation. For example, the zoom center may be translated while the image is rescaled. Optionally, the displayed image may be rotated about the zoom center. In this way, interesting image features may be better represented in the zoomed image. 
         [0015]    In an embodiment, the system is further arranged for zooming a second image displayed in a second viewport, wherein
       each region of the plurality of regions has a second zoom function associated with the region for zooming the second image, and   the zoom unit is further arranged for zooming the second image based on the zoom input, using the second zoom function associated with the selected region.       
 
         [0018]    This is useful, for example, in mammography, where mirrored images of the right and left breast are displayed, each in its own viewport, and zoomed simultaneously based on a zoom input provided for the right or left breast. The viewports may be combined into a single display area. 
         [0019]    In an embodiment of the system, the second zoom function is based on the zoom function associated with the selected region in the image and a map of the viewport into the second viewport, wherein the zoom center of the second zoom function associated with the selected region is obtained by mapping the zoom center of the zoom function associated with the selected region into the second viewport using said mapping. The second zoom scale of the second zoom function is computed based on the zoom scale of the zoom function. For example, the two scales may be identical. 
         [0020]    Advantageously, the system of the invention may be used for digital mammography. 
         [0021]    In a further aspect, the invention provides an image acquisition apparatus comprising an embodiment of the disclosed system. 
         [0022]    In a further aspect, the invention provides a workstation comprising an embodiment of the disclosed system. 
         [0023]    In a further aspect, the invention provides a method of zooming an image displayed in a viewport, wherein the image comprises a plurality of regions, each region of the plurality of regions having a zoom function associated with the region, the method comprising:
       an input step for receiving a region input for selecting a region of the plurality of regions and for receiving a zoom input for zooming the image; and   a zoom step for zooming the image based on the zoom input, using the zoom function associated with the selected region.       
 
         [0026]    In a further aspect, the invention provides a computer program product to be loaded by a computer arrangement, comprising instructions for zooming an image displayed in a viewport, wherein the image comprises a plurality of regions, each region of the plurality of regions having a zoom function associated with the region, the computer program product, after being loaded, providing said processing unit with the capability to carry out steps of an embodiment of the disclosed method. 
         [0027]    It will be appreciated by those skilled in the art that two or more of the above-mentioned embodiments, implementations, and/or aspects of the invention may be combined in any way deemed useful. 
         [0028]    Modifications and variations of the image acquisition apparatus, of the workstation, of the method, and/or of the computer program product, which correspond to the described modifications and variations of the system or of the method, can be carried out by a person skilled in the art on the basis of the description. 
         [0029]    A person skilled in the art will appreciate that an image dataset in the claimed invention may be a 2-dimensional (2-D), 3-dimensional (3-D) or 4-dimensional (4-D) image dataset, acquired by various acquisition modalities such as, but not limited to, X-ray Imaging, Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Ultrasound (US), 
         [0030]    Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), and Nuclear Medicine (NM). 
         [0031]    The invention is disclosed in the independent claims. Advantageous embodiments are disclosed in the dependent claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    These and other aspects of the invention will become apparent from and will be elucidated by means of the implementations and embodiments described hereinafter and with reference to the accompanying drawings, wherein: 
           [0033]      FIG. 1  shows a block diagram of an exemplary embodiment of the system; 
           [0034]      FIG. 2  shows regions of an image, defined on the basis of a partition of the viewport; 
           [0035]      FIG. 3  shows regions of an image, defined on the basis of object delineation; 
           [0036]      FIG. 4  illustrates an embodiment of the system for concurrently zooming mirrored images of the right and the left breast; 
           [0037]      FIG. 5  shows a flowchart of exemplary implementations of the method; 
           [0038]      FIG. 6  schematically shows an exemplary embodiment of the image acquisition apparatus; and 
           [0039]      FIG. 7  schematically shows an exemplary embodiment of the workstation. 
       
    
    
       [0040]    Identical reference numerals are used to denote similar parts throughout the Figures. 
       DETAILED DESCRIPTION OF EMBODIMENTS 
       [0041]      FIG. 1  schematically shows a block diagram of an exemplary embodiment of the system  100  for zooming an image displayed in a viewport, wherein the image comprises a plurality of regions, each region of the plurality of regions having a zoom function associated with the region, the system comprising:
       an input unit  110  for receiving a region input for selecting a region of the plurality of regions and for receiving a zoom input for zooming the image; and   a zoom unit  120  for zooming the image based on the zoom input, using the zoom function associated with the selected region.       
 
         [0044]    The exemplary embodiment of the system  100  further comprises:
       a segmentation unit  130  for defining the image object;   a control unit  160  for controlling the work of the system  100 ; and   a memory unit  170  for storing data.       
 
         [0048]    In an embodiment of the system  100 , there are three input connectors  181 ,  182  and  183  for the incoming data. The first input connector  181  is arranged to receive data coming in from a data storage means such as, but not limited to, a hard disk, a magnetic tape, a flash memory, or an optical disk. The second input connector  182  is arranged to receive data coming in from a user input device such as, but not limited to, a mouse or a touch screen. The third input connector  183  is arranged to receive data coming in from a user input device such as a keyboard. The input connectors  181 ,  182  and  183  are connected to an input control unit  180 . 
         [0049]    In an embodiment of the system  100 , there are two output connectors  191  and  192  for the outgoing data. The first output connector  191  is arranged to output the data to a data storage means such as a hard disk, a magnetic tape, a flash memory, or an optical disk. The second output connector  192  is arranged to output the data to a display device. The output connectors  191  and  192  receive the respective data via an output control unit  190 . 
         [0050]    A person skilled in the art will understand that there are many ways to connect input devices to the input connectors  181 ,  182  and  183  and the output devices to the output connectors  191  and  192  of the system  100 . These ways comprise, but are not limited to, a wired and a wireless connection, a digital network such as, but not limited to, a Local Area Network (LAN) and a Wide Area Network (WAN), the Internet, a digital telephone network, and an analog telephone network. 
         [0051]    In an embodiment of the system  100 , the system  100  comprises a memory unit  170 . The system  100  is arranged to receive input data from external devices via any of the input connectors  181 ,  182 , and  183  and to store the received input data in the memory unit  170 . Loading the input data into the memory unit  170  allows quick access to relevant data portions by the units of the system  100 . The input data comprises the image data, the region input and the zoom input. Optionally, the input data may comprise instructions for the segmentation unit  130 . The memory unit  170  may be implemented by devices such as, but not limited to, a register file of a CPU, a cache memory, a Random Access Memory (RAM) chip, a Read Only Memory (ROM) chip, and/or a hard disk drive and a hard disk. The memory unit  170  may be further arranged to store the output data. The output data comprises the zoomed image data. The memory unit  170  may be also arranged to receive data from and/or deliver data to the units of the system  100  comprising the input unit  110 , the zoom unit  120 , the segmentation unit  130 , and the control unit  160 , via a memory bus  175 . The memory unit  170  is further arranged to make the output data available to external devices via any of the output connectors  191  and  192 . Storing data from the units of the system  100  in the memory unit  170  may advantageously improve performance of the units of the system  100  as well as the rate of transfer of the output data from the units of the system  100  to external devices. 
         [0052]    In an embodiment of the system  100 , the system  100  comprises a control unit  160  for controlling the system  100 . The control unit  160  may be arranged to receive control data from and provide control data to the units of the system  100 . For example, after receiving a region input for selecting a region of the plurality of regions and a zoom input for zooming the image, the input unit  110  may be arranged to provide control data “the input data has been received” to the control unit  160 , and the control unit  160  may be arranged to provide control data “zoom the image” to the zoom unit  120 . Alternatively, a control function may be implemented in another unit of the system  100 . 
         [0053]    In an embodiment, the invention is used by a physician for viewing an image of the left breast.  FIG. 2  shows the left breast image in a viewport. There are two image regions, first image region  1  and second image region  2 , defined on the basis of a partition of the viewport by a partition line  20 . Such definition of regions is useful in the case of x-ray mammography, where the breast image is shown in the viewport in a standardized way. The first region  1  is located near the chest wall. The second region  2  comprises the remaining part of the image, not included in the first region  1 . The user may use the mouse to provide the region input and the zoom input. In an embodiment, the user may move the pointer to point at a location in the image and click the mouse button, thereby selecting a viewport location. Further, the user may use the mouse wheel to zoom in or out the image. If the selected location  211  is included in the first region  1 , the first region  1  is selected and the zoom function is the function associated with the first region  1 . The zoom center of the zoom function associated with the first region  1  is at the location  212 , which is the intersection of the horizontal crossing the selected location  211  and the left viewport border line. In this way, the user can view an area of the breast tissue near the chest wall. If the user selects a location  22  in the second region  2 , the second region  2  is selected and the zoom function is the function associated with the second region  2 . The selected location  22  becomes the zoom origin of the zoom function associated with the second region  2 . 
         [0054]    In an embodiment of the system, the selected region is further defined based on an image object displayed in the viewport and the spatial relation between the viewport location and the object. This embodiment is illustrated in  FIG. 3 . There are three image regions  1 ,  2 ′ and  3 ′, defined on the basis of a partition of the viewport by a partition line  20  and a partition curve  30 . Such a definition of the regions is useful in the case of x-ray mammography, where the breast image is shown in the viewport in a standardized way. The partition curve  30  may be defined relative to the viewport. Alternatively, the partition curve may be defined based on image segmentation by the breast skin shown in the image displayed in the viewport. The segmentation can be performed manually, semi-automatically or automatically. A person skilled in the art will be able to choose and implement a suitable segmentation method. 
         [0055]    As in the previous embodiment illustrated in  FIG. 2 , the user may use the mouse to provide the region input and the zoom input by, in succession, moving the mouse pointer to point at a location in the image, clicking the mouse button, thereby selecting the location, and further using the mouse wheel to zoom in or out the image. The zoom functions associated with regions  1  and  2 ′ are the same as described above for regions  1  and  2  in  FIG. 2 , respectively. A third zoom function is associated with region  3 ′. If the selected location  311  is in the third region  3 ′, the third region  3 ′ is selected and the zoom function is the function associated with region  3 ′, the zoom center of this zoom function is at the location  312 , which is a location defined by the intersection of the normal to the partition curve  30  crossing the selected location  311  and the partition curve. Thus, selecting a location in the third region  3 ′, the user can zoom in an area of the breast near the selected portion of the skin. 
         [0056]    Optionally, the zoom center may be visualized by a marker as illustrated in  FIGS. 2 and 3 . 
         [0057]    In an embodiment, the system  100  is further arranged for zooming a second image displayed in a second viewport, wherein each region of the plurality of regions has a second zoom function associated with the region for zooming the second image, and the zoom unit  120  is further arranged for zooming the second image based on the zoom input, using the second zoom function associated with the selected region. This is useful, for example, in mammography, where mirrored images of the right and left breast are displayed, each in its own viewport, and zoomed simultaneously based on a zoom input provided on the basis of the right or left breast.  FIG. 4  shows the right breast image in the viewport  41  and the left breast image in the second viewport  42 . The viewports are combined into a single display area. By providing a region input and a zoom input for zooming the image, the second image is zoomed concurrently with the image, using derived zooming parameters based on the same inputs and the associated second zoom function. 
         [0058]    In an embodiment of the system  100 , the second zoom function is based on the zoom function associated with the selected region in the image and a map of the viewport into the second viewport for mapping the zoom center of the zoom function associated with the selected region into the zoom center associated with the second zoom function. This embodiment is illustrated also in  FIG. 4 , wherein the map is the mirror reflection of the viewport  41  over the ‘symmetry’ line  40  into the second viewport  42 . The second zoom function is thus defined by the zoom center  421  which is the mirror image of the zoom center  411 . 
         [0059]    Although the embodiments of the invention have been described with reference to x-ray mammography images, a person skilled in the art will understand that the invention is useful for interacting with other images. Examples of such images include, but are not limited to, MRI brain scans and PET images of the lungs. 
         [0060]    Those skilled in the art will further understand that other embodiments of the system  100  are also possible. It is possible, among other things, to redefine the units of the system and to redistribute their functions. For example, there may be several segmentation units  130 , each implementing a different segmentation technique. Although the described embodiments apply to medical images, other applications of the system, not related to medical applications, are also possible. 
         [0061]    The units of the system  100  may be implemented using a processor. Normally, their functions are performed under the control of a software program product. During execution, the software program product is normally loaded into a memory, like a RAM, and executed from there. The program may be loaded from a background memory, such as a ROM, hard disk, or magnetic and/or optical storage, or may be loaded via a network like the Internet. Optionally, an application-specific integrated circuit may provide the described functionality. 
         [0062]    An exemplary flowchart of the method M of zooming an image displayed in a viewport, wherein the image comprises a plurality of regions, each region of the plurality of regions having a zoom function associated with the region, is schematically shown in  FIG. 5 . The method M begins with an optional segmentation step S 05  for defining an object in the image. Alternatively, or after the segmentation step S 05 , the method M is arranged for performing an input step S 10  for receiving a region input for selecting a region of the plurality of regions and for receiving a zoom input for zooming the image. After the input step S 10 , the method M continues to a zoom step S 20  for zooming the image based on the zoom input, using the zoom function associated with the selected region. After the zooming S 20  step, the method M terminates. 
         [0063]      FIG. 6  schematically shows an exemplary embodiment of the image acquisition apparatus IAA employing the system SYS of the invention, said image acquisition apparatus IAA comprising an image acquisition unit IAA 10  connected via an internal connection with the system SYS, an input connector IAA 01 , and an output connector IAA 02 . This arrangement advantageously increases the capabilities of the image acquisition apparatus IAA, providing said image acquisition apparatus IAA with advantageous capabilities of the system SYS. 
         [0064]      FIG. 7  schematically shows an exemplary embodiment of the workstation WS. The workstation comprises a system bus WS 01 . A processor WS 10 , a memory WS 20 , a disk input/output (I/O) adapter WS 30 , and a user interface WS 40  are operatively connected to the system bus WS 01 . A disk storage device WS 31  is operatively coupled to the disk I/O adapter WS 30 . A keyboard WS 41 , a mouse WS 42 , and a display WS 43  are operatively coupled to the user interface WS 40 . The system SYS of the invention, implemented as a computer program, is stored in the disk storage device WS 31 . The workstation WS is arranged to load the program and input data into memory WS 20  and execute the program on the processor WS 10 . The user can input information to the workstation WS, using the keyboard WS 41  and/or the mouse WS 42 . The workstation is arranged to output information to the display device WS 43  and/or to the disk WS 31 . A person skilled in the art will understand that there are numerous other embodiments of the workstation WS known in the art and that the present embodiment serves the purpose of illustrating the invention and must not be interpreted as limiting the invention to this particular embodiment. 
         [0065]    It should be noted that the above-mentioned embodiments illustrate rather than limit the invention and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” does not exclude the presence of elements or steps not listed in a claim or in the description. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements and by means of a programmed computer. In the system claims enumerating several units, several of these units can be embodied by one and the same record of hardware or software. The usage of the words first, second, third, etc., does not indicate any ordering. These words are to be interpreted as names.