Method for visualizing a bone

Abstract

A method and a corresponding system are provided. The method comprises steps of providing 2D images and subsequently detecting outlines of a primary structure in each of the images. A visual representation of the 2D images is generated and the 2D images are then arranged as 2D slices in a 3D visual representation. To this end, at least two of the 2D images are taken at different imaging angles. The method provides a 3D visual representation of a region of interest comprising a primary structure to support a spatial sense of a user.

Claims

1. A method for visualizing a bone, in particular a femur or a hip bone, the method comprising: providing 2D images of the bone wherein at least two of these 2D images are taken at different respective imaging orientations with respect to the bone, detecting outlines of a primary structure in the 2D images of the bone, generating visual representations of the 2D images based on the outlines, and displaying the visual representations of each of the 2D images simultaneously as a plurality of corresponding 2D slices arranged in a 3D visual representation for supporting a spatial sense of a user, wherein each of the 2D slices is arranged in the 3D visual representation, such that, from a perspective of a viewpoint of the 3D visual representation, an angle defined between a surface normal of each 2D slice and a surface normal of every other one of the 2D slices is the same as a respective angle defined between the imaging orientations of the corresponding 2D images.

2. The method according to claim 1, wherein the primary structure is at least one of a bone and a bone fragment.

3. The method according to claim 1, wherein the primary structure is at least one of an implant and a reference body.

4. The method according to claim 1, further comprising the steps of: detecting at least three markers in the 2D images, wherein a marker is one of a reference body, a part of a reference body, an implant or a bone shape, and determining a spatial arrangement of the primary structure based on the position of the at least three markers, wherein the step of arranging the visual representation of the 2D images in the 3D visual representation is based on the determined spatial arrangement.

5. The method according to claim 1, further comprising the step of: classifying the primary structure into a class of implants, a class of bones, a class of bone fragments and/or a class of reference bodies, wherein the step of arranging the visual representation of the 2D images in the 3D visual representation is based on the classification of the primary structure.

6. The method according to claim 5, wherein the visualization of the primary structure is limited to at least one of the classes of implants, bones, bone fragments and/or reference bodies.

7. The method according to claim 1, wherein the 3D visual representation is rotatable showing the visual representations of the 2D images from different viewpoints.

8. The method according to claim 1, wherein the visualization of the primary structure is based on a detection of a predetermined surgery step, wherein detection of the predetermined surgery step is based on a number and a position of primary structures in the 2D images.

9. The method according to claim 1, wherein the 2D images are X-ray images.

10. A system for visualizing a bone, in particular a femur or a hip bone, comprising: a detection unit, and a processing unit, wherein the detection unit is configured to provide 2D images of the bone, wherein at least two 2D images are taken at different respective imaging orientations with respect to the bone, wherein the detection unit is further configured to detect outlines of a primary structure in the 2D images of the bone, wherein the processing unit is configured to generate visual representations of the 2D images based on the outlines, and wherein the processing unit is further configured to display the visual representations of each of the 2D images simultaneously as a plurality of corresponding 2D slices arranged in a 3D visual representation to support a spatial sense of a user, each of the 2D slices being arranged in the 3D visual representation, such that, from a perspective of a viewpoint of the 3D visual representation, an angle defined between a surface normal of each 2D slice and a surface normal of every other one of the 2D slices is the same as a respective angle defined between the imaging orientations of the corresponding 2D images.

11. A non-transitory computer readable medium encoded with a computer program, which, when executed by a processor, performs the method steps according to claim 1.

12. The method according to claim 1 wherein only two 2D images of a femur are used with the two 2D images taken at angles of at least 15 from one another.

13. The method according to claim 12 wherein the two 2D images are x-ray images.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a flow chart of steps of a method according to an embodiment of the invention.

(2) FIG. 2 shows an example of a monitor visualization of a 2D X-ray image according to an embodiment of the invention.

(3) FIGS. 3A and 3B show schematic illustrations of a monitor visualization of a 3D visual representation according to an embodiment of the invention.

(4) FIG. 4 shows another flow chart of steps of a method according to an embodiment of the invention.

(5) FIG. 5 shows a schematic illustration of a system according to an embodiment of the invention.

(6) FIGS. 6A and 6B are schematic visualizations regarding a projection of a reference body.

DETAILED DESCRIPTION

(7) The flow chart in FIG. 1 illustrates method steps performed in accordance with embodiments of the invention. It will be understood that the steps described may be major steps, wherein these major steps might be differentiated or divided into several sub-steps. Furthermore, there might be also sup-steps between the steps. Consequently, groups of steps may be related to a major aspect which may also be performed separately, i.e. independent from other steps or groups of steps.

(8) It is noted that some steps are described as being performed if necessary. This is intended to indicate that those steps may be omitted. It is in particular noted that a computer program element according to an embodiment of the invention may comprise sets of instructions to automatically recognize if a step is necessary or not, and to automatically proceed with the next actually necessary step.

(9) With reference to FIG. 1, the exemplary method starts with providing 2D images of a region of interest in step S1. A region of interest may be a bone and the anatomic structures surrounding the bone. The images may be X-ray images. Alternatively, the images may be ultrasound images, magnetic resonance images or may be given by any other type of images acquired in medical diagnostics and/or therapy. In method step S2 outlines of a primary structure are detected in each of the 2D images of the bone. Thereby, an outline may be the shape of a primary structure in the respective image. Accordingly, an outline can be given by a contour line of the respective primary structure in the image. Detection of an outline can be carried out by e.g. comparing the grey-level value of neighbouring pixels or clusters of pixels in an image, thereby determining contour lines and in particular determining contour lines, which define the edge or boundary of a structure in the image, i.e. the boundary of a structure with respect to another structure depicted in the image.

(10) A primary structure can be a bone and/or a bone fragment. Further, a primary structure can be given by an implant and/or a reference body. In context of the invention, a primary structure is a structure of interest during a surgical procedure. For instance, a femur or a hip bone, a corresponding implant and/or a bone screw can be primary structures in a 2D image provided in step S1 of a method according to the invention. Accordingly, a non-primary structure is a structure, which is of minor of no relevance in a specific surgical procedure. Tissue surrounding e.g. a hip bone, may, for instance be a non-primary structure, which can be of minor relevance for a surgeon during fixing of an implant in a hip bone.

(11) In optional method step S, the detected primary structures can, if necessary, be classified into different classes, e.g. a class of implants, a class of bones and/or a class of markers or reference bodies. It may be possible that only those primary structures comprised in a specific selectable class or several selectable classes are visually represented in later method steps S3 and S4.

(12) In method step S3, visual representations of each of the 2D images provided in step S1 are generated, based on the outlines detected in step S2. These visual representations of 2D images are subsequently arranged in a 3D visual representation in method S4. This is done by arranging the 2D images as corresponding 2D slices in a 3D visualisation. Each slice is arranged according to the angles under which the 2D image is taken. An example of such an arrangement is described in more detail in context of FIGS. 3A and 3B below.

(13) In FIG. 2, an example of a visualisation of a 2D image on a monitor or display is shown. The image comprises a bone 1 with a corresponding bone fragment or bone part 2. Further, an implant 3 is shown, as well as a drilling tool 4. A plurality of markers 5 is visible in FIG. 2. The latter markers allow determination of a spatial order and/or arrangement of the further structures visible in the image. With respect to FIGS. 6A and 6B a method is explained below that allows determination of a spatial arrangement from one single image.

(14) In FIG. 3A a schematic example of a 3D visual representation 10 displayed on a monitor or display 6 is shown. The 3D visual representation 10 comprises several 2D planes or 2D slices 20. On each 2D plane corresponding image information, i.e. information from a corresponding 2D image is displayed. Thereby, the 2D planes are arranged in the 3D visual representation reflecting the angles under which the 2D images were acquired. Accordingly, there is an angle between the surface normal of the two planes in FIG. 3A.

(15) The 3D visual representation may be rotatable. The possibility of rotating the representation, i.e. the representation of the planes in FIG. 3A is indicated by arrows 21 and 22. This possibility may further provide assistance to a surgeon, supporting his spatial sense to capture the 3D arrangement of a surgical area without the need to display all 3D information of the area but only slices or cuts through this area. Exemplarily, in order to put the idea across, a cuboid 30 is shown as a 3D structure in FIG. 3A. Only the solid lines 31, 32, which show the intersection of the cuboid 30 with the 2D planes, are displayed according to the invention. The dashed lines of the cuboid 30 are not shown, but only given in FIG. 3A to illustrate the idea.

(16) FIG. 3B shows a further schematic example of a 3D visual representation 10 displayed on a monitor 6. The 3D visual representation comprises several 2D planes, which are arranged in parallel to each other with a certain space between them. Arrows 21 and 22 indicate that the 3D visual representation may be rotatable. Further, the solid lines 31, 32 are contour lines of a cuboid 30, similar to the cuboid shown in FIG. 3A. However, in contrast to FIG. 3A, in FIG. 3B only the contours or the outline of the cuboid in the 2D planes 20 is shown.

(17) Thus in FIG. 3A, the surgeon will know that the object visualised on the display (reference sign 6) is a cuboid (reference sign 30). However, the cuboid will not be displayed (the dashed lines will not be visible to the surgeon according to the invention). What will actually be shown on the display are the thick lines 31 and 32 only. Using his spatial sense, the surgeon can however reconstruct the position and orientation of the cuboid 30, although only the thick black lines 31 and 32 are shown on the display. In FIG. 3B a similar situation as in FIG. 3A is shown. Here the hashed planes are visualised on the display. The surgeon knows that these planes belong to a cuboid and can deduce, using his imagination (spatial sense), the position and orientation of the cuboid, relying on the depicted information.

(18) The flow chart in FIG. 4 illustrates method steps performed in accordance with another embodiment of the invention. In method step S1, 2D images are provided and in each of these images outlines of at least one primary structure are detected in subsequent method step S2. Optionally, the detected primary structures can then be classified into one of the classes of implants, bones, bone fragments, reference bodies and/or markers.

(19) In the subsequent step S2, at least three markers are detected in each of the 2D images. Based on the position and angles under which these markers are detected in each of the 2D images, a spatial arrangement of the primary structures in each 2D image is determined. An example, how such determination may be performed, is given below with reference to FIGS. 6A and 6B. After the spatial arrangement of the primary structures is determined, a visual representation of the 2D images is generated in subsequent method step S3. The latter visual representation of all or a part of the 2D images is arranged in a 3D visual representation as 2D slices or 2D planes.

(20) FIG. 5 shows an exemplary embodiment of a system 9 according to an embodiment of the invention. Substantially, necessary for performing the steps of the method, a processing unit 100 is part of the device.

(21) An exemplary imaging device or imaging unit 200 includes an X-ray source, and an X-ray detector 260, wherein these two units are mounted on a C-arm 220.

(22) Furthermore, the system 9 in FIG. 5 includes an input unit 300, by means of which for example an intended imaging direction may be manually entered. Further, a user can input structures, which shall be considered as primary structures in the images. Also shown is a connection to a database 600, located for example in a network. The database 600 may comprise information regarding anatomical structures, for example from 3D scans of different anatomical structures, so that the imaged anatomical structure may be compared with this information so as to determine or identify specific anatomical structures. The database may further comprise information regarding a sequence of necessary and/or possible steps of a surgical procedure. Further, the database can comprise a storage comprising at least one or a series of earlier acquired reference images. It is noted that it is also possible to automatically determine the progress of the surgical procedure based on detectable aspects in an x-ray image, wherein such aspects may be in instrument and/or implant.

(23) Finally, there is an indication in FIG. 5 of an anatomical structure of interest 500 as well as of a reference object 64 formed by a plurality of radiopaque spheres. Within said anatomical structure, for example a bone of a patient may be located which may be subject to the described procedures.

(24) With reference to FIGS. 6A and 6B, a method to determine a spatial arrangement of objects in a 2D image is explained in the following.

(25) FIG. 6A shows a reference body formed, in the example, by four spheres 640, 641, 642, 643 being arranged in space in a predetermined way. Further shown are lines representing x-ray beams emitted by an x-ray source 240, 241, respectively. Each line ends on one of the projection surfaces denoted as AP (anterior-posterior) or ML (medio-lateral). On the projection surface ML, the spheres of the reference body form a first pattern of projection points 640, 641, 642 and 643, and on the projection surface AP, the spheres form a second pattern of projection points 640, 641, 642 and 643. As can be easily seen, the first pattern on the surface ML differs from the second pattern on the surface AP. A skilled person will appreciate that it is possible to arrange spheres of a reference body in three-dimensional space such that a unique projection pattern will be achieved for each projection direction. Consequently, it is possible to determine the imaging direction, based on the detected projection pattern, and to determine the actual orientation of the reference body in space in relation to the imaging device. Furthermore, as the beams follow a fan angle, the spatial position, i.e. the distances of the references body to the x-ray source and the x-ray detector, respectively, can be calculated based on measured distances of the projection points. In fact, it is merely a matter of geometry to calculate the actual position and orientation of the reference body based on a single projection of the same.

(26) With the reference body as a spatial anchor, it is also possible to determine an actual position and orientation of an anatomical structure based on a single x-ray image, as schematically illustrated in FIG. 6B. Here, a projection of a head 500 of a femur, i.e. of a ball head is shown on each of the projection surfaces, wherein the relation of the projection 500 to the projections of the reference body on the surface ML differs from the relation of the projection 500 to the projections of the reference body on the surface AP. This illustrates that the projections of the reference body and the relation to the anatomical structures in the projection image are unique for each imaging direction. Consequently, the spatial position and orientation of the reference body can be determined and also the spatial position and orientation of the anatomical structure in the vicinity of the reference body, based on one x-ray image.

(27) While embodiments have been illustrated and described in detail in the drawings and afore-going description, such illustrations and descriptions are to be considered illustrative or exemplary and not restrictive, the invention is not limited to the disclosed embodiments.

(28) Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practising the claimed invention, from a study of the drawings, the disclosure and the appended 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 fulfil the functions of several items recited in the claims.

(29) The mere fact that certain measures are recited and mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The computer program may be stored/distributed on a suitable medium such as an optical storage medium or a solid-state medium supplied together with or as a part of another hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

(30) Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.