Patent Publication Number: US-2019167225-A1

Title: Orientation reference system for medical imaging

Description:
CROSS-REFERENCE TO PRIOR APPLICATIONS 
     This application is a continuation of application Ser. No. 14/116,151, filed Nov. 7, 2013, which is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/IB2012/052259, filed on May 7, 2012, which claims the benefit of European Patent Application No. 11166065.0, filed on May 13, 2011. These applications are hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to positioning a medical imaging system in relation to an object. In particular, the present invention relates to a medical imaging apparatus, a display apparatus for displaying medical image data of an object, an imaging system, and a method for positioning a medical imaging system. 
     BACKGROUND OF THE INVENTION 
     Medical imaging is commonly performed, for example, during operational procedures, such as in a hospital. To acquire image data of an object under investigation or examination from different directions, an image acquisition device can be moved in relation to the object. To provide a surgeon, for example, with image information about the current situation, for example during an interventional procedure, images are provided, for example, on a display. In case the surgeon requires image data from a different region of interest, or from a different direction, the image acquisition device and the object, for example a patient, are moved in relation to each other such that further images can be acquired from a different position. Usually, this is performed by an image acquisition operator. Thus, a respective instruction has to be communicated to the operator. However, instructions by the surgeon may be misleading, for example an instruction like “move upwards”, which may refer to the displayed image as well as to the image acquisition device itself. Thus, it has been shown that after a further image acquisition step, still further adjustment instructions concerning the position of the image acquisition device in relation to the patient are quite often necessary. An imaging system is described in WO 2008/120121 A1, wherein an adjustment of the table in relation to the imaging unit is provided to maintain the region of interest within the image region of the imaging unit in response to a rotation of the imaging unit about an axis of rotation, to assure that the region of interest is within the image area of after rotating the imaging unit. 
     SUMMARY OF THE INVENTION 
     There is a need to provide improved positioning possibilities which facilitate the workflow during an intervention. 
     The object of the present invention is solved by the subject-matter of the independent claims, wherein further embodiments are incorporated in the dependent claims. 
     It should be noted that the following described aspects of the invention apply also for the medical imaging apparatus, the display apparatus, the imaging system, and the method for positioning a medical image system. 
     According to a first aspect of the invention, a medical imaging apparatus is provided, comprising an image acquisition arrangement, and an output unit. The image acquisition arrangement is positionable in relation to an object to acquire image data of the object from different directions. For the positioning, the image acquisition arrangement is movable in relation to the object in at least two movement directions. The output unit is arranged to provide the image data. First movement direction indicators are provided to indicate possible movement directions of the image acquisition arrangement in relation to the object. 
     In relation with the present invention, the term “direction” refers to movement possibilities, which movements comprise translations and rotations, i.e. translational and rotational movements, as well as combinations thereof. Thus, the term “movement direction indicator” refers to movement possibilities and can thus be understood as “movement possibilities indicator”. 
     For example, the image acquisition arrangement is movable in relation to the object by translational movement. As another example, the image acquisition arrangement is movable in relation to the object by rotational movement. Still further, the image acquisition arrangement is movable in a combination of rotation and translation. 
     The rotational movement, the translational movement as well as the combinations thereof, can be provided in a plane as one- or two-dimensional movement. The rotational movement, the translational movement as well as the combinations thereof, can also be provided in space as three-dimensional movement. 
     According to an exemplary embodiment of the invention, the image acquisition arrangement is an X-ray imaging device with an X-ray source and an X-ray detector. 
     According to a further exemplary embodiment, the first movement direction indicators are provided on the image acquisition arrangement such that they are visible to the user. 
     According to a further exemplary embodiment, the first movement direction indicators are provided next to a control interface for accomplishing the positioning. 
     According to a further exemplary embodiment, the first movement direction indicators are provided such that a bijective identification of the complementary direction is possible. 
     According to a second aspect of the invention, a display apparatus for displaying medical image data of an object is provided, comprising a display area and a movement direction indication. The display area is configured to display image data of an object provided by an image acquisition arrangement. The movement direction indication is configured to provide second movement direction indicators in relation to the displayed image data of the object to indicate possible movement directions of the image acquisition arrangement in relation to the object. 
     According to a further exemplary embodiment, the movement direction indication is configured to be updated after a positioning movement. 
     According to a third aspect of the invention, an imaging system is provided, comprising a medical imaging apparatus according to one of the above described aspects and embodiments, and a display apparatus according to one of the above described aspects and embodiments. The output unit is configured to provide the image data to the display apparatus. The movement direction indication on the display apparatus relates to the movement possibilities of the image acquisition arrangement. The first movement direction indicators and the second movement direction indicators are equivalent. 
     According to a further exemplary embodiment, the first and the second movement direction indicators are of the same type. 
     According to a fourth aspect of the invention, a method for positioning a medical image system is provided, comprising the following steps: a) providing first movement direction indicators indicating possible movement directions of an image acquisition arrangement in relation to an object; b) displaying image data of the object, and providing second movement direction indicators in relation to a displayed image data of the object, which second movement direction indicators indicate the different movement directions of the image acquisition arrangement; wherein the first and the second movement direction indicators are equivalent; c) identifying at least one of the second movement direction indicators for an intended movement of the image acquisition arrangement; and d) accomplishing the intended movement of the image acquisition arrangement in relation to the object on behalf of at least one of the first movement direction indicators which is equivalent to the identified second movement direction indicator. 
     According to an aspect of the invention, for example, in case of an operational intervention, the surgeon is provided with direction indicators that can be used for instructing the required movements in case of a desired (re-) positioning or (re-) adjustment of the image acquisition device. Since, for the performance of the positioning or adjustment of the image acquisition device, equivalent direction indicators are provided, for example to the operator responsible for accomplishing the positioning procedure, it is possible to give clear and direct instructions which cannot be misinterpreted, but which rather result in a precise positioning for further image acquisition steps. According to an aspect of the invention, an orientation reference system is thus provided, which is presented on the one hand to the (first) user via providing movement direction indicators on the display, and on the other hand presented to a staff member (as second user) responsible for accomplishing the actual movement of the image acquisition device or arrangement, in form of further movement direction indicators, both of which indicator groups are equivalent to each other, thus forming an orientation reference system according to the invention. The inventive orientation reference system provides improved positioning possibilities facilitating the workflow during an intervention. In particular, in case of X-ray imaging, the orientation reference system saves unneeded, and thus unwanted, X-ray radiation procedures, thereby reducing the overall amount of radiation to which the patient is exposed to, due to the improved positioning and alignment commands provided by the equivalent movement direction indicators. 
     These and other aspects of the present invention will become apparent from and elucidated with reference to the embodiments described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention will be described in the following with reference to the following drawings. 
         FIG. 1  illustrates a medical imaging apparatus according to an exemplary embodiment of the invention; 
         FIG. 2  illustrates a display apparatus according to an exemplary embodiment of the invention; 
         FIG. 3  illustrates an imaging system according to an exemplary embodiment of the invention; 
         FIG. 4  illustrates a further exemplary embodiment of a medical imaging apparatus; 
         FIG. 5  shows a further exemplary embodiment of a medical imaging apparatus; 
         FIGS. 6A to 6E  illustrate examples of movement direction indicators; 
         FIG. 7  illustrates basic steps of a method according to an exemplary embodiment of the invention; and 
         FIGS. 8A to 8C  illustrate further aspects of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows a medical imaging apparatus  10  with an image acquisition arrangement  12  and an output unit  14 . The image acquisition arrangement  12  is positionable in relation to an object  16  to acquire image data  18  of the object  16  from different directions. For example, the object  16  is a patient. For the positioning, the image acquisition arrangement  12  is movable in relation to the object in at least two movement directions, which is indicated by a double arrow  20 . The output unit  14  is arranged to provide the image data  18 . 
     According to the invention, first movement direction indicators  22  are provided to indicate possible movement directions of the image acquisition arrangement in relation to the object. 
     According to a further exemplary embodiment, although not further shown in  FIG. 1 , for the movement of the image acquisition arrangement in relation to the object, the image acquisition arrangement is movable. 
     The image acquisition arrangement may be movable by a direct interaction of the user or an operator, for example by manual actuation of the positioning. The movement can also be accomplished with the aid of mechanical movement devices or actuators, such as electro-magnetic or pneumatic driving devices. 
     The relative movement of the image acquisition arrangement in relation to the object can also be accomplished by a movement of the object itself, for example, with a moveable object support device, such as a movable patient table. 
     The relative movement can also be accomplished by both moving the image acquisition arrangement and the object itself. 
     According to the present invention, the first movement direction indicators, which will be discussed in more detail below, allow an identification of the different movement directions, and thus allow to address, as well as to perform, a movement of the image acquisition arrangement in relation to the object for the image acquisition of the object from different directions or different positions. 
       FIG. 2  shows a display apparatus  24  for displaying medical image data of an object. The display apparatus  24  comprises a display area  26  and a movement direction indication  28 . The display area  26  is configured to display image data  30  of an object, for example a patient, provided by an image acquisition arrangement. 
     The term “image data” refers to directly detected image data as well as to processed image data. For example, image as detected is shown on the display. The detected information may also be transformed by image processing steps, such as digital subtraction steps, e.g. based on previously acquired image data. The detected information may also be transformed or processed into further image information such as a generated model, a segmented structure or the like. 
     The movement direction indication  28  is configured to provide second movement direction indicators  32  in relation to the displayed image data of the object to indicate possible movement directions of the image acquisition arrangement in relation to the object. For example, four second movement direction indicators  32  are shown. Of course, other numbers of the first and second movement direction indicators are also possible. 
     For example, the movement direction indication is configured to provide the second movement direction indicators  32  according to the correlation of the orientation of the displayed image to the orientation of a detector of the image acquisition arrangement. 
     According to a further aspect of the invention, the second movement direction indicators on the display apparatus correlate with the movement directions of the image acquisition arrangement in correlation with the image plane of the displayed image. 
     The first movement direction indicators  22  and the second movement direction indicators  32  will also be explained in the following. 
       FIG. 3  shows an imaging system  34  with a medical imaging apparatus  10  and a display apparatus  24 , which have already been described in basic aspects above. 
     As an example for a medical imaging apparatus  10 , the image acquisition arrangement  12  is an X-ray imaging device  36  with an X-ray source  38  and an X-ray detector  40 . For example, the X-ray imaging system device  36  may be a C-arm device, as shown for exemplary purposes in  FIG. 3 . The C-arm device as shown, for example, may comprise a C-arm structure  42 , to which both ends the detector  40  and the X-ray source  38  are mounted. The C-arm structure  42  is movably mounted to a support  44 , in which the C-arm is slideably mounted. The support  44  also allows rotational movement around a horizontal axis  46 . The support  44  is mounted to a suspended arm structure  48  with an L-shape, shown only for exemplary purposes. The L-arm structure  48  is mounted to a support  50 , which is mounted to the ceiling of the operational theatre and allows a horizontal movement along support rails  52  as well as a rotational movement around a vertical axis  54 . 
     The C-arm device is provided such that an object  56  can be located between the detector  40  and the X-ray source  38 , in a way that, due to the different moving possibilities of the C-arm, image acquisition of the object  56  is possible from a number of different directions, which are not further shown. 
     The object  56  is arranged on a support device, for example a patient table  58 , allowing horizontal and vertical adjustment for further positioning and adjustment purposes. Therefore, the table  58  is supported by a respective adaptable stand  60 . 
     The display apparatus  24  is provided in the vicinity of the patient table, for example by being mounted to a ceiling support  62 , which allows position adjustment of the display apparatus  24 , according to the user&#39;s needs. 
     Further, adaptable lighting  64  is indicated, as well as an input or control interface  66  for adjusting peripheral equipment, such as the lighting  64  or the table  58 . 
     Further, a control arrangement  68  is shown in the foreground, which comprises a plurality of display devices  70 , as well as a plurality of input devices, for example a keyboard  72 , a mouse  74 , a graphic tablet  76 , as well as an input device  78  with a joystick  80 . 
     The control interface  78  may be provided for accomplishing a positioning of the medical imaging apparatus, for example the C-arm device. For example, the movement of the C-arm may be actuated and controlled by the joystick, with which positioning commands can be entered to control the medical imaging apparatus. 
     The first movement direction indicators  22  are provided on the image acquisition arrangement such that they are visible to the user. For example, the first movement direction indicators are arranged on visible housing parts, such as the housing of the detector, or support parts of the image acquisition arrangement, wherein the housing or support parts are moving in accordance with the position movement. As an example, reference numerals  82  indicate first movement direction indicators  22  provided on the surrounding faces of the housing of the detector  40 . Thus, the first movement direction indicators  22  identify possible movement directions of the image acquisition arrangement. 
     The first movement direction indicators may be referred to as an orientation system of the image acquisition arrangement. 
     According to a further exemplary embodiment of the invention, the first movement direction indicators  22 ,  82  are provided as adaptable movement direction indicators  84 , as is also shown in relation with  FIG. 8 . For example, the first movement direction indicators may be provided as one or more display units with adjustable display content. This allows, for example, adjusting the displayed content, i.e. the adjustment of the first movement direction indicators according to different needs and individual situations. 
     In case the first movement direction indicators are adapted or changed, the second movement direction indicators may be adapted or changed accordingly. 
     Of course, theoretically, the first and second movement direction indicators could be different, but this would mean the necessity of a decoding or translation step on the side of at least one of the users, which could then lead to unwanted misunderstanding. 
     For example, the adaptable first movement direction indicators  84  may be provided as bi-stable displays. These displays only need electric supply for their activation and change of the display content, respectively. That is, once they have been adjusted to show or display the desired information, the electric supply can be disconnected. 
     As already mentioned in relation with  FIG. 2 , the display apparatus  24  comprises the display area  26  to display the image data  30  of the object  56 , which image data  30  is provided by the image acquisition arrangement  10 . 
     For example, the second movement direction indicators  32  are shown in the edge zone of the display area  26 , for example, overlaid to the displayed image data  30 . 
     As an aspect of the invention, the first movement direction indicators  22  and the second movement direction indicators  32  are equivalent. 
     The term “equivalent” refers to the first and second movement direction indicators being synonymic, or being in a predetermined reference to each other, or being comparable. Thus, the term “equivalent” refers to the first and the second movement direction indicators as being corresponding to each other. 
     According to an exemplary embodiment of the invention (not further shown), the first and the second movement direction indicators are of the same type. 
     According to an exemplary embodiment of the invention (not further shown), the first and the second movement direction indicators can have different members, but with the same sort or type of symbols and the same logic. 
     By providing the medical imaging apparatus and the display apparatus with a common orientation reference system in form of the first and second movement direction indicators, it is possible that a surgeon, for example, studying the displayed image of the object, for example of a patient, finds movement direction indicators next to the image such that he or she can identify a desired movement direction of the image acquisition arrangement in relation to the object for further acquisition steps. Thus, for determining the further necessary movement of the apparatus in relation with the patient, these directions can correctly be addressed, which means relieve with respect to the user&#39;s time and attention needed to identify the movement direction. 
     Once the surgeon has identified the desired movement direction, the repositioning or adjustment of the position of the image acquisition apparatus can easily be accomplished by a staff member responsible for operating the device, for example a technician. For example, in case of a direct manual actuation of the positioning, i.e. by direct interaction with the C-arm itself, the technical operator finds the equivalent movement direction indicator on the housing of the detector, for example, such that he or she directly knows in which direction the image acquisition arrangement has to be moved for further acquisition steps. 
     Showing the orientation information on the device and on the display is also helpful for the surgeon to move the C-arm in the right direction himself 
     By providing the first movement direction indicators next to the control interface  78 , for example next to the joystick  80 , as indicated with small dots  86 , it is also possible to enter a respective control command by the joystick  78  by simply receiving the respective movement command in form of the second movement direction indicator, and to look for the equivalent first movement direction indicator next to the joystick  78 . 
     Of course, the first movement direction indicators  22  could also be provided on the monitor or displays  70 , the graphic tablet  76 , or also in relation with the mouse  74  or the keyboard  72 . 
     The first and second movement direction indicators will further be explained in relation with  FIGS. 6A to 6E . 
     Before explaining the movement direction indicators, it is referred to  FIG. 4 , showing an ultrasound device  85  as a further example for an image acquisition arrangement. The ultrasound device  85  has a movable transducer unit  87  to be moved along an object  90 , for example a patient, wherein the first movement direction indicators are provided on the outside of the transducer unit  87  as indicated with reference numeral  92 . As further shown, the ultrasound device  85  may be connected to a processing unit  94 , for example by a wire connection, which could also be provided as a wireless connection. Further, a display  98  can be connected to the processing unit  94 , as schematically indicated with a connection line  100 . The display  96  provides the second movement direction indicators  32 , for example in the surrounding of a displayed ultrasound image  102 . Of course, the second movement direction indicators  32  could also be provided as overlay to the ultrasound image  102 . This allows to identify a movement direction by looking at the ultrasound image  102  and then to identify the necessary movement of the, for example, handheld movable transducer unit  87  by looking for the equivalent of the first movement direction indicators  92 . It is also possible to have one person conducting the movement of the transducer unit  87 , and another person studying the ultrasound image  102 , to identify the necessary movements which will then be conducted by the first person. 
       FIG. 5  shows a further example of an image acquisition arrangement in form of a steerable catheter device  104  with a handheld control device  106  to move and steer a catheter  108  inside an object structure  110 , for example inside a patient&#39;s vessel structure or other tubular structure. First movement direction indicators, indicated with reference numeral  112 , are provided on the outside of the control device  106  next to the control or regulation mechanism. The steerable catheter device may provide image data to a processing unit  114 , connected to the catheter device by a wire connection or wireless connection  116 , which processing unit  114  is further connected to a display  118  by a further connection  120 . Second movement direction indicators  32  may be provided next to an image  122 . Thus, the movement directions for next image acquisitions may be identified by looking at the display  118 , which movement directions can then be identified on behalf of the equivalent first movement direction indicators  112  as provided on the handheld control device  106 . 
     According to a further example (not shown), a stiff endoscope is provided, which, for example, can be used in arthroscopy or laparoscopy, in which similar first movement direction indicators are provided, as well as second movement direction indicators. The orientation, given by the movement direction indicators, facilitates, for example, the orientation for the user to move the endoscope in the desired direction. 
     According to an aspect of the present invention, the movement direction indicators are provided such that a bijective identification of the complementary direction is possible. In the context of the present invention, the complementary direction is the opposite direction, i.e. the same line in a plan or in space, but with an opposite orientation. This, and also the following passages, may apply for the first and/or the second movement direction indicators. 
     For example, the coding of the movement direction indicators is provided such that in case of partly hidden movement direction indicators, the non-visible movement direction indicators can be identified. For example, in such case where a surgeon is standing on one side of an image acquisition arrangement, being able to see only a part of the provided movement direction indicators, and an operator responsible for the positioning of the imaging apparatus is standing on the other side, where the part visible for the surgeon is not visible, but the part hidden for the surgeon is visible, both users can identify the respective movement direction indicator as seen from the other user. 
     According to a further aspect of the invention, the movement direction indicators are provided as denominated symbols such that the movement directions are addressable with unambiguous messages. The messages may be used in a communicatively way. For example, the messages may be terms such as spoken words, for example commands. The messages may also be gestures conducted by the surgeon. For example, the terms are common words to be called by both user identifying desired or intended movement direction and an operator initiating the movement, for example to confirm the respective movement command. 
     According to the present invention, the movement direction indicators relate to different movement directions such that opposing directions are indicated with different denominated symbols, clearly allowing an identification of the respective movement direction. 
     According to a further exemplary embodiment of the invention, the movement direction indicators are provided for a movement plane, wherein the movement direction indicators are provided as a planar orientation coding  150 , as will be described with reference to  FIGS. 6A to 6D . 
       FIG. 6A  shows a medical image, for example an X-ray image  152 , in which, as second movement direction indicators, a surrounding chromatic circle  154  is shown with four different colours  154   a ,  154   b ,  154   c , and  154   d . For example, the four colours are arranged such that the respective opposite colour is provided as a complementary colour. 
       FIG. 6B  shows the second movement direction indicators as dotted coding  156  with a first dot symbol  156   a , a second dot symbol  156   b , a third dot symbol  156   c , and a fourth dot symbol  156   d . The dot symbols are provided such that respective opposite symbols show the sum 7 in total. Thus, by only being able to see one part of the symbols, the respective opposite symbols can be identified. 
       FIG. 6C  shows a cardinal direction system  158  with a letter “N” as first cardinal direction indicator  158   a , an “E” as second cardinal direction  158   b , an “S” as third cardinal direction  158   c , and a “W” as fourth cardinal direction  158   d.    
       FIG. 6D  shows clock positions  160  with the clock numbers “3”, “6”, “9”, and “12” arranged around the X-ray image  152 . 
     The movement direction indicators may also be provided relating to two-dimensional Cartesian coordinate system. 
     According to a further exemplary embodiment of the invention, the second (and first) movement direction indicators relate to a spatial movement in relation to an image plane, wherein the movement direction indicators are provided as a spatial orientation coding  162 . 
     According to a further example, numerical indicators  164  of a virtual dice are shown wherein the dice has n faces. The numerical indicators are arranged such that the sum of opposing numerical indicators is n+1. As indicated in  FIG. 6E , four numerical indicators  164   a  to  164   d  are arranged around the X-ray image  152 . A fifth numerical indicator  164   e  and a sixth numerical indicator  164   f  are provided in combination with a three axis graph  166  indicating the plane of the image with a horizontal axis  168  and a vertical axis  170 , and the direction in the depth of the image plane with a further third axis  172 . The direction from the image plane towards the user, i.e. in the opposite direction than the depth direction  172 , a still further arrow  174  is shown in a dotted manner. Thus, all directions of a dice with six faces are provided, wherein the respective opposing faces sum up to the number of seven to provide the possibility to identify the respective complementary direction. 
     The terms “up”, “down”, “right”, “left”, “depth” etc. relate to the image plane, and thus the detector plane and not to an actual position. 
     According to a further example, although not further shown, the spatial movement can also result in spatial orientation coding in form of a spherical colour model. For example, complementary colours are oriented on opposing sides of the spherical colour model. 
     The first and second movement direction indicators may be provided relating to a three-dimensional Cartesian coordinate system. The movement direction indicators may further be provided relating to a cylindrical or spherical coordinate system. The movement direction indicators may also be referred to as orientation symbols. 
     It is explicitly noted that the above described aspects in relation with the second movement direction indicators shown in the context of the displayed image, also apply for the first movement direction indicators as well. In particular, the first and second movement direction indicators are provided such that a bijective identification of the complementary direction is possible. The first and the second movement direction indicators thus correlate with the movement direction of the image acquisition apparatus. 
     As indicated above, according to an exemplary embodiment of the invention (not further shown), the display area may be configured to provide the second movement direction indicators in combination with the image data. For example, the second movement direction indicators may be provided superimposed at the edge areas of the display area. The display arrangement may also comprise an orientation area at the edge or outside of the display area in order to provide the movement direction indicators. Of course, the provision of an edge area outside of a display arrangement can also be provided in combination with overlaid indicators to an actually displayed image. 
     In the following, basic steps of a method  200  shall be explained with reference to  FIG. 7 . In a provision step  210 , first movement direction indicators  212  indicating possible movement directions of an image acquisition arrangement in relation to an object are provided. In a further step, a displaying sub-step  214  is provided in which image data  216  of the object is displayed. In a further provision sub-step  218 , second movement direction indicators  220  are provided in relation to the displayed image data of the object, which second movement direction indicators indicate the different movement directions of the image acquisition arrangement. The displaying sub-step  214  and the provision sub-step  218  may also be provided as two parallel steps, which is also indicated with a dotted separation line  221 . 
     According to the present invention, the first and the second movement direction indicators  212 ,  220  are equivalent to each other, which is indicated by a wave-like line with double arrows  222 . 
     In an identification step  224 , at least one of the second movement direction indicators  220  for an intended movement of the image acquisition arrangement is identified. Further, in an accomplishment step  226 , the intended movement of the image acquisition arrangement in relation to the object is accomplished on behalf of at least one of the first movement direction indicators which is equivalent to the identified second movement direction indicator. Thus, the second movement direction indicator identified in the identification step  224  is so-to-speak transferred to the first movement direction indicators  212  to identify the respective equivalent, which is indicated by a dotted arrow  227 . 
     The first provision step  220  may also be referred to as step a), the displaying and provision sub-steps  214 ,  218  may also be referred to as step b), the identification step  224  as step c), and the accomplishment step  226  as step d). 
     According to a further exemplary embodiment, the movement direction indication is configured to be updated after a positioning movement. 
     According to an example, not further shown, a movement of the medical imaging apparatus in relation with the object is detected and the respective information is provided to the display, where the second movement direction indicators are updated such that the actual position of the imaging apparatus in relation with the object is presented in form of the position of the second movement direction indicators in relation to the image of the object. For example, a C-arm is rotated in relation to the object for x degrees for positioning. Thus, a second indicator, on the display, showing a certain movement possibility of the C-arm is rotated respectively in relation to the image of the object on the display; i.e. in case the image is kept unchanged, the second indicator is rotated also for x degrees. 
     According to a further example, also not shown, a movement of the medical imaging apparatus in relation with the object is detected and the respective information is provided to the display. Further, a new image is acquired and the image data is provided on the display. The second movement direction indicators are updated such that the actual position of the imaging apparatus in relation with the object is presented in form of the position of the second movement direction indicators in relation to the (new) image of the object. 
     According to a further example, also not shown, a movement of the image in relation to the display can also be reflected in an update of the second movement direction indicators. For example, an image is rotated for 90 degrees for better understanding, leaving the C-arm at its position. The second movement direction indicators are also rotated, together with the image, for 90 degrees. 
     The update may be provided after a positioning movement and a further image data acquisition. For example, after the accomplishment step  226 , a further image acquisition step  228  is provided to acquire image data which can then be used for updating the image data in the displaying step  214 . This is indicated with an arrow  230  from the further image acquisition frame  228  to the frame  214 . However, it must be noted that the update feature is not a necessary feature of the method as described in relation with  FIG. 7 , which is indicated with a line separation symbol  232 , indicating that the update is a possible add-on but not an essential feature. Once the image data is updated, also the second movement direction indicators are updated in relation to the displayed image data of the object. 
     For example, in case of a movement of the image due to a further image acquisition of the positioning, the second movement direction indicators are arranged, e.g. positioned or amended in their content shown to the user, according to the movement of the image acquisition apparatus itself. For example, in case of a rotation or mirroring of the image acquisition arrangement, the second movement direction indicators are also rotated or mirrored to match with the new image. 
     The image acquisition arrangement may be configured to acquire image data in a projection or image plane, and the second movement direction indicators relate to movement in relation to the projection plane, for example, with the projection plane and/or relating to the depth of the projection plane 
     Before referring to  FIGS. 8A to 8C , some further aspects are described in the following. 
     In case of an interventional C-arm procedure, X-ray images may be taken from any direction. The C-arm can be moved from a projection position to the projection position by a C-arm operator under instruction of a user, for example a surgeon. The communication between the user of a C-arm operator is facilitated with the present invention by providing the user and the C-arm operator with the same and consistent orientation information related to the last acquired X-ray image as well as the orientation information being visible on the C-arm itself. Thus, position adjustments can be clearly defined by both user and C-arm operator, thus improving the general understanding of the C-arm orientation and also the communication between the user and the C-arm operator. Consequently, the time needed, or consumed so-to-speak, for the X-ray image acquisition, can thus be significantly reduced. As another advantage of the present invention, it must be noted that the invention also allows the reduction, or nearly elimination, of superfluous use of X-ray, since unnecessary X-ray image acquisitions are prevented. 
     In particular, in case the C-arm is operated from a lateral position with respect to the patient anatomy, which most of the times results in a necessary rotational adjustment of the X-ray images on the X-ray monitor to ensure usual interpretation of the projected anatomy by the user in an upright orientation (head-up), or also possible mirroring of the displayed image, the clear definition in which direction to move the C-arm in order to achieve a desired projection, is facilitated according to the present invention, thus improving the overall workflow during a C-arm interventional procedure. 
     In particular, aspects such as the rotation and/or mirroring of the image on the X-ray monitor, the hindered sight of the C-arm operator to the operation field during position adjustment, the small visible area of the operation field, for example in case the patient is completely covered with sterile drapes, and in particular also instructions of the surgeon to move the C-arm in a certain direction that can be misleading, as an instruction like “move upwards” may refer to the displayed X-ray image as well as to the C-arm itself, which can represent different adjustment directions, are greatly relieved by the present invention by the provision of a common orientation reference system for the image acquisition arrangement itself and in relation with the displayed image presented to the surgeon. 
     According to the present invention, the visible clarification of the X-ray image orientation on the X-ray monitor and the according directions on the C-arm itself, or the respective input or control device like a joystick, saves time and reduces the amount of superfluously acquired X-ray images. 
     The present invention is feasible, for example, for mobile C-arms in particular, which are operated from the back of the system for position adjustments, which hinders the view to the operation field for the C-arm operator and therefore especially lack of visible orientation information on the C-arm in relation to the acquired mostly rotated X-ray projections on the X-ray monitor. Thus, according to the present invention, misunderstandings between user and C-arm operator are prevented, as well as the correct position adjustment of the C-arm is ensured. 
     According to a further aspect of the present invention, it is also provided to present orientation symbols, or in other words first movement direction indicators, on several locations on a C-arm, for example, to ensure that at least a part of one of the respective sets of symbols is visible to the user. In case the detector shows the first movement direction indicators, it is also possible to provide a sterile coverage with clear drapes to ensure the visibility of the system during surgical or interventional procedures. 
     Of course, it is possible to provide different types and different numbers of first and second movement direction indicators. For example, in case flat detectors with a rectangular shape are used, and thus having four visible sidewalls of a housing, these can be equipped with a respective number of symbols marking the respective directions. In case of cylindrical image intensifiers, also three, or four, five, etc., of the first and second movement direction indicators could be provided. Of course, in case the system is equipped with a reduced number of movement possibilities, the movement direction indicators are adapted accordingly in their numbers and also in their content with respect to the bijective decoding aspect. 
     As shown in  FIG. 8A , an X-ray image  180  showing a spinal structure  182  in horizontal manner is shown on a display  184 . The X-ray image  180  is provided by a C-arm device which is only partly shown in  FIGS. 8A to 8C . However, a detector  186  is shown which is provided with first movement direction indicators  188 , showing “12 h” and “3 h”, thus relating to clock positions as described in relation with  FIG. 6D . 
     Next to the X-ray image  180 , respective second movement direction indicators  190  are provided, which second movement direction indicators are provided such that the respective movement direction in relation to the image content shown in the X-ray image  180  has the same correlation as the respective movement indicator on the detector with respect to the object, for example the patient, under investigation. In other words, the detector having the “12 o&#39;clock” symbol  12   h  on the side facing towards the head of the patient, as indicated with reference numeral  192 , is also presented next to the spinal structure indicating the same direction. 
     As shown in  FIG. 8B , for a better understanding of the image content shown, the X-ray image  180  is usually rotated such that the respective direction “12 o&#39;clock” of the spinal structure is arranged so-to-speak with the head-up of the patient. If the surgeon is now studying the image content and wishes to have an X-ray image from an area of the spinal structure closer to the neck, i.e. in relation with a patient to move the image a bit more upwards, he or she can simply give a command to have an X-ray image from a position after a movement in the “12 o&#39;clock” direction. The C-arch operator can then move the C-arch in a respective direction by simply manually moving the X-ray apparatus in a respective direction, which is the direction visible to a person standing on the opposite side of the surgeon in case of  FIGS. 8A to 8C , or to enter a respective command, as described before. 
     In case the surgeon wishes to have an X-ray image from a position further down the spinal structure, he or she simply has to say “move to 6 o&#39;clock”. Despite the 6 o&#39;clock symbol not being visible to a person standing on the other side, due to the bijective identification, the operator for moving the C-arch knows that the 6 o&#39;clock is opposite to the 12 o&#39;clock, thus facilitating the interaction as required. 
     Similar is the case, for example, if the surgeon wishes to receive information on the side of the image indicated with the 9 o&#39;clock information. He or she can then give the movement direction “more to 9 o&#39;clock” in order to make the C-arm operator move the C-arm respectively and to acquire a further image as shown in  FIG. 8C , in which the spinal structure, here indicated with reference numeral  194 , a bit more to the right side with reference to the display area. 
     It has to be noted that embodiments of the invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method type claims whereas other embodiments are described with reference to the device type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters is considered to be disclosed with this application. However, all features can be combined providing synergetic effects that are more than the simple summation of the features. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. 
     Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims. 
     In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items re-cited in the claims. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.