3D Measurement Mesh Tool for X-ray Images

Abstract

A method for calculating a scaled virtual mesh for an x-ray projection image includes: providing at least first and second registered x-ray projection images Ij-j=1,2,... of a patient’s desired anatomical structure (step S1); defining two points P1 and P2 of the desired anatomical structure in three-dimensional space and thereby determining the three-dimensional coordinates of the two points P1 and P2 using the x-ray projection images (step S2); calculating a scaled virtual mesh based on the determined three-dimensional coordinates of the two points P1 and P2 (step S3); and projecting the calculated mesh onto at least one of the first and second registered x-ray projection images and displaying it to a user (step S4).

Description

Technical Field

[0001] The present invention relates to a method for calculating a virtual mesh for scaling an x-ray projection image, an apparatus for calculating such a virtual mesh for scaling an x-ray projection image, a system for calculating such a virtual mesh for scaling an x-ray projection image, and a program unit for such a method. Background Technology

[0002] Mobile X-ray fluoroscopy for imaging objects is known in the prior art and is widely used in various fields, such as orthopedics, trauma, vascular surgery, and spine. Due to its design, mobile X-ray fluoroscopy is characterized by its smaller footprint, greater operability, and lower cost compared to fixed X-ray systems. Depending on the required information about the object, several images must sometimes be taken and analyzed. Physicians use these images as a basis for preparing for surgery to obtain information about the size of appropriate implants (e.g., screws). Therefore, during X-ray imaging, an object of known size is typically superimposed on the patient's desired anatomy. When the object is not parallel to the detector plane, or if the area of ​​the anatomy is not in the plane of the object, the estimated distance is less reliable, and the measurement lacks accuracy.

[0003] For the inventors of this invention, it is now apparent that there is a need to improve the analysis of X-ray images from such a mobile X-ray fluoroscopy device. Specifically, there is a need to improve the efficiency of obtaining geometric information by analyzing the X-ray images from such a mobile X-ray fluoroscopy device. Summary of the Invention

[0004] Therefore, the object of the present invention is to provide a method and system capable of efficient analysis of X-ray images, such as those from a mobile X-ray fluoroscopy device. This object and other objects (which are further mentioned in the following description or may be recognized by those skilled in the art) are addressed by the subject matter of the independent claims. Further embodiments and advantages of the invention are incorporated in the dependent claims.

[0005] The described embodiments similarly relate to methods, computing devices, systems, computer program units, and computer-readable media. Different combinations of embodiments may produce synergistic effects, although these may not be described in detail.

[0006] Furthermore, it should be noted that all embodiments of the method of the present invention can be performed in the order of the described steps; however, this is not necessarily the only and necessary order of the steps of the method. The method presented herein can be performed in an alternative order of the disclosed steps without departing from the corresponding method embodiments, unless the opposite is explicitly mentioned below.

[0007] Technical terms are used according to their common sense. If a term expresses a specific meaning, its definition will be given below in the context in which it is used.

[0008] According to a first aspect of the invention, a method is provided for calculating a virtual mesh for scaling an x-ray projection image. The method includes: providing at least first and second registered x-ray projection images I of a patient's desired anatomical structure. j , j = 1, 2, ... (step S1), define two points P1 and P2 of the desired anatomical structure in three-dimensional space and thereby determine the three-dimensional coordinates of the two points P1 and P2 using X-ray projection images (step S2), calculate a scaled virtual mesh based on the determined three-dimensional coordinates of the two points P1 and P2 (step S3), and project and display the calculated mesh to the user on the X-ray projection images, preferably on at least one of the first and second registered X-ray projection images (step S4).

[0009] The term "scaled virtual mesh" should be interpreted broadly in the context of this invention and includes both rectangular and distorted meshes with a scale. The term "scale" should also be understood as a measure of the virtual mesh, allowing the user / viewer to directly derive measurements, such as distances, from X-ray images of a desired anatomical structure imaged through at least two projection images. Therefore, the viewer does not need to estimate distances in the X-ray images, which means increased accuracy in the analysis. Alternatively, the scale analysis can also be performed algorithmically. Of course, a combination of user-determined measurements and algorithm-determined measurements is also feasible. It should be noted that determining or deriving measurements specifically includes determining or deriving measurements of length or distance. Further details and embodiments of the scaled virtual mesh used in this invention will be provided below in the context of embodiments and, for example, in… Figure 5 and Figure 6 The following is an explanation of the embodiments shown in the detailed description.

[0010] Image registration (specifically, X-ray projection images) is a prior art and is widely used for image acquisition and evaluation. Images providing such registration can include X-ray projection images registered using external sources (e.g., medical databases, other imaging devices, etc.), as well as self-executing registration implemented through algorithms and / or by systems performing the methods described herein. Further description of X-ray projection images providing registration will follow below in the context of specific embodiments and, for example... Figure 3 The embodiments shown will be explained in detail in the following description.

[0011] For the average technical reader, image registration is clearly the process of transforming different images / datasets into a single coordinate system. These images / data can be multiple photographs and / or data from different sensors, at different times, or from different perspectives. It is used in computer vision, medical imaging, and in the compilation and analysis of images and data from satellites. Registration is necessary to compare or integrate images / data obtained from these different measurements. Therefore, the X-ray projection images used in this paper for registration are images that have already been transformed into a single coordinate system.

[0012] The desired anatomical structure to be imaged can have any geometry. The definition of points P1 and P2, and the determination of their three-dimensional coordinates, can be performed by the user (who is interested in the analysis of the desired object's anatomical structure), or alternatively by an algorithm or in combination with an algorithm. Such an algorithm can use patient data and / or an anatomical database to define two points P1 and P2 and determine their three-dimensional coordinates. The user can, for example, provide user input so that the algorithm automatically identifies the femoral head in the first image, and thus automatically determines P1 and its three-dimensional coordinates, as well as P2, relative to the second image.

[0013] Generally, knowledge of three-dimensional coordinates allows for the accurate determination of lengths / distances in an X-ray projection image, not just the distance between two points P1 and P2. Further description of possible ways of defining two points P1 and P2 will follow in the context of specific, non-limiting embodiments and, for example... Figure 4 The embodiments are provided in a detailed description.

[0014] As will become apparent from the detailed description below, in one embodiment, three points P1, P2, and P3 are defined, and their three-dimensional coordinates are determined for the computation of the mesh.

[0015] Furthermore, the calculation of the scaled virtual mesh can be performed using various mathematical methods, as will become apparent from the explanation in the following description of specific embodiments. In the examples, control points ci and intersection lines dij can be calculated in various different ways to determine the scaled virtual mesh.

[0016] The calculated grid is projected onto and displayed to the user on at least one of the first and second registered X-ray projection images, and can be performed on one or more / various displays, such as HMIs using CT, and / or static screens and portable smart glasses using augmented reality technology.

[0017] This aspect of the invention is based on the inventors' insight that during CT imaging, using an object placed on the desired anatomical structure can only provide accurate measurement data for areas located parallel to a plane containing an object of known size, which must also be located in a plane parallel to the X-ray detector. Therefore, every measurement of distances outside the plane containing the known-size object leads to unavoidable inaccuracies. The present invention overcomes these drawbacks. For example, in a particularly preferred embodiment of the invention, distances in an X-ray projection image can be measured for any viewpoint of the anatomical structure without using an additional object of known size. Distances in the region of interest to be measured can be outside the plane parallel to the detector without loss of measurement accuracy. Therefore, using a grid calculated according to the invention, physicians can always derive reliable measurements from X-ray projection images without the need for explicit calibration steps.

[0018] It should be noted that, in the context of this invention, the following indexing convention is used: j represents the image index; i represents the reference point index; and m represents the control point index on the cross line ij. This will become apparent from the following description.

[0019] According to an exemplary embodiment, the step of calculating the scaled virtual mesh (step S3) includes: calculating at least two control points c on the line connecting the defined points P1 and P2. i i = 1, 2, ... (step S3a); calculate the cross line d for each registered image. ij i = 1, 2, ...; j = 1, 2, ... (step S3b), where each intersecting line d ij The control point ci intersects the line connecting the defined points P1 and P2, where each intersecting line d ij Parallel to the detector, image I j It is captured using this detector, and preferably each cross line d ij It is perpendicular to the line connecting the two defined points P1 and P2.

[0020] In a preferred embodiment, at each intersection line d ij Calculate control point k ijm Step (S3c), where control point k ijm For each image I j A virtual grid with limited scaling.

[0021] At each intersection d ij With the generation of the corresponding image I j When the detectors are parallel, the grid is equidistant and does not change the magnification. Further detailed embodiments built upon this method of grid computation can be found, for example, from... Figure 5 and Figure 6 The specific embodiments described in the context are collected.

[0022] Alternatively, the grid can also be defined using three selected points P1, P2, and P3, which define a plane and intersect the line d. ij Located in this plane. Intersecting line d ij The line is perpendicular to the line connecting the defined points P1 and P2, but not parallel to the detector. This can be an advantage when the region of interest lies within a specific plane of the object.

[0023] In other words, another way to define the mesh is to define / select a third anatomical point P3 in the two X-ray images. P3, together with P1 and P2, defines a plane. Then, we use steps S1-S3a to define c. i As explained in detail above and will be further elaborated below, the intersecting line d can then be uniquely constructed within the plane defined by the three points P1, P2, and P3. ij Such a d ij The cross line is perpendicular to line P1P2, but it is no longer parallel to the detector, as in the previously described embodiments. In this method, the grid is calibrated and attached to the plane defined by P1P2P3, as will be clear to those skilled in the art according to this disclosure.

[0024] According to another exemplary embodiment of the present invention, the method includes the following steps: projecting onto a first registered x-ray projection image I1 and displaying it to a user by a control point k. i1m A defined, scaled virtual grid is projected onto the second-registered X-ray projection image I2 and displayed to the user by control point k. i2m A limited, scaled virtual grid.

[0025] In other words, in this embodiment, the calculated grid is overlaid on the first and second registered X-ray projection images I1 and I2 for the user to use on a display. Therefore, the user / viewer has proportional information for analyzing the region of interest in the two registered X-ray projection images I1 and I2.

[0026] According to another exemplary embodiment of the present invention, the method includes calculating the distance between two points P1 and P2 in three-dimensional space, and using the calculated distance to determine at least two control points k. ijm The distance between them.

[0027] The grid scale is determined by defining all control points k. ijm The distance between them is calculated horizontally and vertically. Two adjacent control points k ijmThe distances between them can have any value, but preferably they are equidistant. It is possible that humans can more easily identify or analyze grids with equidistant grid sizes.

[0028] According to another exemplary embodiment of the present invention, the method includes image I j General at least two control points k ijm The determined distance between and control point k ijm They are displayed together to the user.

[0029] Control point k ijm The distances between them can be interpreted as representing a grid and serve as a scale and / or metric for the viewer. Regarding image I... j General control point k ijm The determined distance between and control point k ijm Further descriptions displayed to the user can be easily found in the following text. Figure 5 The examples described and illustrated are collected.

[0030] According to another exemplary embodiment of the invention, the first and second registered X-ray projection images show the patient's desired anatomical structures from different perspectives.

[0031] Different viewpoints enable the capture of various information about the region of interest, such as information hidden in one viewpoint but visible in another. These different viewpoints form the basis for the necessary alignment of points P1 or P2 in the registered X-ray projection images, which further helps in determining the three-dimensional coordinates of points P1 and P2 in space. Further descriptions of the different viewpoints can be found in the embodiments below. Figure 4 It can be found in the detailed description.

[0032] According to another exemplary embodiment of the invention, the method includes positioning an x-ray imaging apparatus in six degrees of freedom, wherein the first and second registered x-ray projection images provided are generated using the x-ray imaging apparatus.

[0033] The positioning or location of an X-ray imaging apparatus is required for the registration of X-ray projection images, which are further processed to generate a virtual mesh. X-ray imaging apparatuses are well known in the prior art, and some examples will be briefly mentioned below. In this embodiment, the X-ray imaging apparatus includes a source and corresponding detectors, which can move interdependently in six degrees of freedom. This means there are fixed geometric constraints between the source and the detectors. The anatomical object is positioned between the X-ray source and the X-ray detector. Therefore, the image of the X-ray imaging apparatus can be aligned using the positional information of the X-ray imaging apparatus, which includes six degrees of freedom.

[0034] According to another exemplary embodiment of the invention, positioning is performed using wavy markings, optical tracking using an X-ray imaging device, an internal encoder of an X-ray imaging device, and / or other image-based markings.

[0035] Therefore, for the same purpose, namely the positioning of X-ray imaging devices in space, there are different opportunities, which can be used individually or in combination for protection achieved through redundancy.

[0036] In another exemplary embodiment of the method, the step of defining two points P1 and P2 of the desired anatomical structure in three-dimensional space (step S2) includes: identifying a first landmark of the desired anatomical structure in a first X-ray projection image (step S2a); determining a first line on which the first landmark lies between the X-ray source and the X-ray detector used to generate the first X-ray projection image (step S2b); identifying a second landmark of the desired anatomical structure in a second X-ray projection image (step S2c); determining a second line on which the second landmark lies between the X-ray source and the X-ray detector used to generate the second X-ray projection image (step S2d); and calculating the three-dimensional coordinates of the intersection of the determined first line and the second line (step S2e). The steps are as follows: 1) The calculated three-dimensional coordinates define point P1 in three-dimensional space; 2) Identify the third landmark of the desired anatomical structure in the first X-ray projection image (step S2f); 3) Determine the third line on which the third landmark lies between the X-ray source and X-ray detector used to generate the first X-ray projection image (step S2g); 4) Identify the fourth landmark of the desired anatomical structure in the second X-ray projection image (step S2h); 5) Determine the fourth line on which the fourth landmark lies between the X-ray source and X-ray detector used to generate the second X-ray projection image (step S2i); and 6) Calculate the three-dimensional coordinates of the intersection of the determined third and fourth lines (step S2j), wherein the calculated three-dimensional coordinates define point P2 in three-dimensional space.

[0037] It should be noted that the steps described in this embodiment, specifically the steps of identifying the landmarks and determining the lines, can be performed manually, for example, based on user input implemented through an HMI, but can also be performed purely automatically using, for example, an image processing algorithm. Of course, a combination of these two alternative methods can also be used without departing from the invention. Furthermore, a particularly detailed embodiment regarding how to use the identification of the landmarks and the determination of the lines to define two points P1 and P2 of a desired anatomical structure in three-dimensional space can be found from, for example... Figure 4 Collected from the corresponding descriptions.

[0038] In another exemplary embodiment, the method includes projecting the determined first line onto a second x-ray projection image, and / or projecting the determined third line onto the second x-ray projection image.

[0039] It should be mentioned that the steps for defining two points P1 and P2 are not limited to lines as geometric tools, which is clear to the average technical reader. Other geometric forms, such as circles and triangles, can also be used to perform this method. Further explanation of defining points can be found in [link to relevant documentation]. Figure 4 The detailed description found therein shows the projection of the determined first line onto the second X-ray projection image.

[0040] In another exemplary embodiment, the projection of the determined first and / or third lines is used as a constraint, for example on a human-machine interface (HMI), which limits the possibility of user input for identifying landmarks in a second x-ray projection image (e.g., on the HMI).

[0041] This constraint limits the alignment used for, for example, P1 in the first and second X-ray projection images, while simultaneously defining or identifying the solution space of P2. Therefore, this constraint benefits HMI users and reduces the potential error rate or increases the accuracy of the grid scale. As mentioned above, the definition of points P1 and P2 can also be automated using algorithms based on patient data or anatomical databases, eliminating the need for user input through the HMI.

[0042] According to another exemplary embodiment, the method includes the step of generating first and second x-ray projection images using an x-ray imaging device (preferably a mobile C-arm CT), the x-ray imaging device including an x-ray source and an x-ray detector.

[0043] Mobile C-arm CT is well-known in the prior art and allows users to easily generate images of a desired object from different perspectives. Further explanation regarding the generation of first and second X-ray projection images can be found in... Figure 3 The detailed description of the illustrated embodiment can be found therein.

[0044] According to another aspect of the invention, an apparatus is provided for calculating a virtual mesh for scaling X-ray projection images. The apparatus includes a computing unit configured to receive at least first and second registered X-ray projection images I of a patient's desired anatomical structure. j ; calculate two points P1 and P2 in the X-ray projection image and the desired anatomical structure, thereby determining the three-dimensional coordinates of the two points P1 and P2; calculate a scaled virtual mesh based on the determined three-dimensional coordinates of the two points P1 and P2; and cause the calculated mesh to be projected onto at least one of the first and second registered X-ray projection images and displayed to the user.

[0045] Such a device can be, for example, a processor, which may be part of an x-ray imaging apparatus (e.g., a mobile C-arm CT scanner) that also includes an x-ray source and an x-ray detector. However, the device for calculating a virtual mesh for scaling the x-ray projection images can also be a separate component that receives images as input and delivers the calculated mesh as output. Furthermore, the computing device itself can project and display the calculated mesh to a user on at least one (preferably two) registered x-ray projection images. Alternatively, the computing device can generate, for example, one or more control signals that cause another device (e.g., a projector or display) to project and display the calculated mesh to a user on one or two or more registered x-ray projection images.

[0046] Another aspect of the invention relates to a system for calculating a virtual grid for scaling an x-ray projection image, comprising the aforementioned means for a virtual grid for scaling an x-ray projection image. It also includes a human-machine interface (HMI) configured to display received first and second registered x-ray projection images and configured to receive input signals from a user, such as landmarks in the displayed image for identifying desired anatomical structures.

[0047] According to another exemplary embodiment, the system includes an x-ray imaging apparatus (preferably a mobile C-arm CT) including an x-ray source and an x-ray detector for generating x-ray projection images.

[0048] It should be noted that the aforementioned parts of the system can be centrally located or distributed among themselves. Centralization means that all parts of the system are at least connected by wires, while distribution means that the parts can communicate with each other in different locations via wireless networks.

[0049] Another aspect of the invention relates to a program unit that, when run on a processor or computer, is configured to perform the method described herein for calculating a virtual grid for scaling an x-ray projection image.

[0050] This program unit can be part of a computer program, but it can also be the entire program itself. For example, this program unit can be used to update an existing computer program to achieve the present invention.

[0051] Another aspect of the invention relates to a computer-readable medium on which such program units as described above are stored.

[0052] A computer-readable medium can be considered as a storage medium, such as a USB stick, CD, DVD, data storage device, hard disk, or any other medium on which program units as described above can be stored. Attached Figure Description

[0053] In the following description, the present disclosure will be illustrated by way of example with reference to the accompanying drawings, in which:

[0054] Figure 1 A flowchart is shown of a method for calculating a virtual grid for scaling an x-ray projection image, according to one embodiment.

[0055] Figure 2 Another embodiment of the method for calculating the scaling of a virtual mesh is illustrated by a flowchart.

[0056] Figure 3 A schematic diagram of a system for calculating a virtual grid for scaling an x-ray projection image, according to one embodiment, is shown.

[0057] Figure 4 The illustration schematically shows how, in an exemplary embodiment, the definition of a point P1 of a desired anatomical structure in three-dimensional space and the determination of the three-dimensional coordinates of that point P1 are performed.

[0058] Figure 5 An exemplary x-ray projection image with a correspondingly superimposed scaled virtual grid is shown according to one embodiment.

[0059] Figure 6 An exemplary x-ray projection image with a correspondingly superimposed scaled virtual grid (the magnification of the scale varies) is shown according to one embodiment.

[0060] It should be noted that these figures are merely schematic representations and are only used to illustrate embodiments of this disclosure. In principle, the same or equivalent elements have the same reference numerals. Detailed Implementation

[0061] Figure 1 A flowchart of a method for calculating a scaled virtual mesh for an x-ray projection image according to an embodiment of the present invention is shown. The steps include: providing at least first and second registered x-ray projection images of a patient's desired anatomical structure (step S1); defining two points P1 and P2 of the desired anatomical structure in three-dimensional space and thereby determining the three-dimensional coordinates of these two points P1 and P2 using the x-ray projection images (step S2); calculating a scaled virtual mesh based on the determined three-dimensional coordinates of the two points P1 and P2 (step S3); and projecting the calculated mesh onto at least one of the first and second registered x-ray projection images and displaying it to the user (step S4).

[0062] In other words, in step S1, at least two registered X-ray projections of the desired anatomical structure from different viewpoints are provided and further used to calculate a scaled mesh. The registered X-ray projections serve as the data basis for the following steps. For the second step S2, the different viewpoints of the registered X-ray projections are necessary, where two points are selected and defined in the region of interest of each registered X-ray projection image. To determine the three-dimensional coordinates of these two points, alignment is performed between each selected point and the corresponding position in the other registered X-ray projection image. Using the positional information of each point in these two registered X-ray projection images, the three-dimensional coordinates of each point of the desired anatomical structure in three-dimensional space can be determined. The three-dimensional coordinates of these two points serve as the basis for a scaled mesh of the anatomical structure, which is designed in step S3. In the final step S3, the designed scaled mesh is projected onto the registered X-ray projections, meaning it is superimposed on the registered X-ray projections. Therefore, a calibrated scaled mesh superimposed on the two registered X-ray projections exists and is displayed to the user.

[0063] It should be noted that the calculation of the scaled virtual mesh can be performed using various mathematical methods, which will utilize... Figure 2 The two embodiments described in the context are used to illustrate this. Furthermore, projecting and displaying the calculated mesh to the user on at least one of the first and second registered X-ray projection images can be performed on one or more displays, such as HMIs using CT, and / or static screens and portable smart glasses using augmented reality technology.

[0064] This method is based on the inventor's insight that during CT imaging, using an object placed on the desired anatomical structure provides accurate measurement data only for areas located parallel to an object of known size within a plane, where the known-size object must also be located within a plane parallel to the X-ray detector. Therefore, every measurement of the distance outside the plane of the known-size object, where the known-size object is located within a plane parallel to the X-ray detector, results in unavoidable inaccuracies. Figure 2 The method overcomes these drawbacks. For example, in a particularly preferred embodiment of the invention, distances in an X-ray projection image can be measured without using an additional object of known size for any viewpoint of the anatomical structure. Distances in the region of interest to be measured can be outside a plane parallel to the detector without loss of measurement accuracy. Therefore, using the method according to Figure 2 The grid calculated using this method allows physicians to obtain reliable measurements from X-ray projection images without explicit calibration procedures.

[0065] Figure 2Another embodiment of the method for calculating the scaled virtual mesh is illustrated by a flowchart. In this embodiment, step S3 is further divided into the following sub-steps: calculating at least two control points c on the line connecting the defined points P1 and P2. i i = 1, 2, ... (step S3a); calculate the cross line d for each registered image. ij i = 1, 2, ...; j = 1, 2, ... (step S3b), where each intersecting line d ij At control point c i The point intersects the line connecting the defined points P1 and P2, where each intersecting line d ij Parallel to the detector, image I j It is captured using this detector, and preferably each cross line d ij Perpendicular to the line connecting the two defined points P1 and P2; and at each intersection d ij Calculate control point k ijm (S3c), where control point k ijm For each image I j A virtual grid with limited scaling.

[0066] In other words, draw a line between two points P1 and P2, where this line serves as the center line in the grid. This line is further divided into segments, starting from point c. i To define (step S3a). These segmented sections are limited to a mesh size in one direction. The calculated intersection line d ij Passing through point c i And perpendicular to the center line, and parallel to each other (step S3b). Each intersecting line d ij Display the calculated point k ijm (Step S3c). These points define the grid size in the second direction. Thus, a calibrated scaled grid is obtained for the X-ray projection image of the desired anatomical structure.

[0067] Alternatively, the grid can also be defined using three selected points P1, P2, and P3, which define a plane and intersect the line d. ij Located in this plane. Intersecting line d ij The line is perpendicular to the line connecting the defined points P1 and P2, but not parallel to the detector. This can be an advantage if your region of interest lies within a specific plane of the object. In other words, another way to define the mesh is to define / select a third anatomical point P3 in the two X-ray images. P3, together with P1 and P2, defines a plane. Then, we use steps S1-S3a to define c. iAs explained in detail above and will be further elaborated below, the intersecting line d can then be uniquely constructed within the plane defined by the three points P1, P2, and P3. ij Such a d ij The cross line is perpendicular to P1P2, but it is no longer parallel to the detector, as in the previously described embodiments. In this method, the grid is calibrated and attached to the plane defined by P1P2P3, as will be clear to those skilled in the art according to this disclosure.

[0068] Figure 3 A schematic diagram of a system 10 for calculating a virtual grid for scaling an x-ray projection image, according to a preferred embodiment, is shown. System 10 includes a mobile C-arm CT scanner comprising an x-ray source 11 and an x-ray detector 12 mounted on a C-arm 13. The C-arm 13 is movable in six directions: three translational and three rotational. The desired anatomical structure is positioned at the center of the C-arm such that the x-ray source 11 can emit radiation toward the desired anatomical structure, and the corresponding x-ray detector 12 can detect the emitted radiation affected by the desired anatomical structure. An x-ray projection image of the desired anatomical structure is thus acquired. Using the positional information of the C-arm 13, the x-ray projection image is registered using various computational methods (not shown). The corresponding positional information of the six spatial coordinates of the C-arm is acquired via so-called ripple markers (not shown). The system also includes a human-machine interface (HMI) 14 configured to display the received first and second registered x-ray projection images and configured to receive input signals from a user for identifying landmarks in the displayed image of the desired anatomical structure. The nature and purpose of boundary markers will be determined from Figure 4 As will become apparent from the description of the illustrated embodiments.

[0069] The system also includes a computing unit 15, which is configured to receive at least first and second registered X-ray projection images of the patient's desired anatomical structures. j The calculation unit calculates two points P1 and P2 in the X-ray projection image and the desired anatomical structure, thereby determining the three-dimensional coordinates of the two points P1 and P2. Based on the determined three-dimensional coordinates of the two points P1 and P2, the calculation unit can calculate a scaled virtual mesh and cause it to be projected onto at least one of the first and second registered X-ray projection images and displayed to the user. In other words, the calculation unit 15 is responsible for all steps of mesh calculation as well as controlling the projection and display of the mesh to the user.

[0070] Figure 4A schematic diagram 20 illustrates the definition of a point 29 of a desired anatomical structure 23 in three-dimensional space and the determination of the three-dimensional coordinates of that point 29. The process includes: identifying a first landmark 29 of the desired anatomical structure 23 in a first X-ray projection image 26 (step S2a); determining a first line 35 on which the first landmark 29 lies between the X-ray source 22 and the X-ray detector 24 used to generate the first X-ray projection image 26 (step S2b); identifying a second landmark 28 of the desired anatomical structure 23 in a second X-ray projection image 27 (step S2c); determining a second line 31 on which the second landmark 28 lies between the X-ray source 21 and the X-ray detector 25 used to generate the second X-ray projection image 27 (step S2d); and calculating the three-dimensional coordinates of the intersection of the determined first line 31 and the second line 35 (step S2e), wherein the calculated three-dimensional coordinates define a point P1 in three-dimensional space 32.

[0071] In other words, the desired anatomical structure 23 is located between x-ray sources 21, 22 and the corresponding x-ray detectors 24, 25. Lines 33, 34, 36, and 37 should provide information about the optical path between x-ray sources 21, 22 and the corresponding x-ray detectors 24, 25. The two x-ray sources 21, 22 and the corresponding x-ray detectors 24, 25 are actually one x-ray source and one x-ray detector of the same C-arm CT, differing only in their view of the desired anatomical structure. At the location of x-ray detector 24, a first-view x-ray projection image 26 is displayed, which should indicate that the x-ray projection image is always related to the location of the corresponding x-ray source / x-ray detector, obtained via wavy markers 32. In practice, the user selects a point / landmark 29 via an HMI (not shown), and the x-ray projection image 26 is displayed on the HMI. In the next step, a calculation unit (not shown) calculates the first line 35 between the point / landmark 29 and the x-ray source 22. In the next step, a portion of the first line 35 located between lines 33 and 34 is projected onto a second x-ray projection image 27. The second x-ray projection image corresponds to the x-ray source 21 and x-ray detector 25 from a second viewpoint of the desired anatomical structure 23. Projection line 30 on the second x-ray projection image 27 serves as a constraint, on which a landmark / point 28 can be located for user selection. Two landmarks / points 28 and 29 represent the same feature of the desired anatomical structure from only different viewpoints. After selecting the landmark / point 28 in the second x-ray projection image 27, line 31 is calculated between the x-ray source 21 and the landmark / point 28. The three-dimensional coordinates of the landmark / point in three-dimensional space are derived from the intersection of lines 31 and 35.

[0072] Figure 5An exemplary portion 40 of an X-ray projection image with an overlaid, scaled virtual grid is shown. This portion 40 of the X-ray projection image includes a first X-ray projection image 41 and a second X-ray projection image 42, which show the same desired object from two different perspectives. The desired object is located below grids 51 and 61, respectively. Furthermore, implants 46 and 58 are shown with overlaid orientation lines 48 and 62. Points 43 and 55 and points 44 and 56 represent selected points from user input, defining the region of interest and used to construct the scaled grid. Lines 49 and 63 are defined by points 43, 55 and 44 and 56. The scaled grid 50 includes horizontal and vertical lines and has millimeter-scale proportions in the horizontal directions 50 and 59 and the vertical directions 51 and 60. Points 43, 44, and 47 also serve as orientation aids for the user in the second X-ray projection image 42 and represent orientation lines 54, 53, and 52 in the top view. Therefore, it is easier for the user to visualize the changes in perspective corresponding to the X-ray projection image.

[0073] Figure 6 Exemplary portion 70 of x-ray projection images 71 and 72 is shown, featuring an overlaid, scaled virtual grid with varying magnification. Furthermore, the implant is also shown in both x-ray projection images 71 and 72. This grid, as described above, includes two points 73 and 74 that define line 75 and are further used in the construction of the scaled grid. Figure 5 Conversely, grid 76 changes its magnification from bottom 78 to top 79, meaning that the grid does not have equidistant grid sizes. This is due to the selection of points 73 and 74 that are not parallel to the detector (not shown).

[0074] By studying the accompanying drawings, this disclosure, and the appended claims, those skilled in the art will be able to understand and implement other variations of the disclosed embodiments when practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. A single processor or other unit can implement the functions of several items or steps recited in the claims. The fact that certain measures are recited only in mutually different dependent claims does not mean that a combination of these measures cannot be used for benefit. Computer programs may be stored / distributed on suitable media, such as optical storage media or solid-state media provided with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems. Any reference numerals in the claims should not be construed as limiting the scope of the claims.

[0075] List of reference numerals in the attached diagram:

[0076] 10 System

[0077] 11, 21, 22 X-ray sources

[0078] 12, 24, 25 X-ray detectors

[0079] 13 C-arm

[0080] 14 HMI

[0081] 15 Computing Units

[0082] 20. A schematic diagram defining a point.

[0083] 23 objects

[0084] X-ray projection images of 26, 27, 41, 42, 71, and 72.

[0085] Points 28, 29, 38, 43, 44, 47, 55, 56, 57, 73, 74: boundary markers, intersections

[0086] 30 Projected lines

[0087] Lines 31 and 35

[0088] 32. Wavy markings

[0089] Optical paths 33, 34, 36, and 37

[0090] Part of the 40 and 70 X-ray projection images

[0091] 45, 50, 59, 60, 78, 79 ratio

[0092] 46, 58, 77 implants

[0093] 48, 62 Implant Orientation Lines

[0094] 49, 75 center lines

[0095] Grids 51, 61, and 76

[0096] Orientation lines 52, 53, and 54

Claims

1. A method for calculating a virtual mesh for scaling an x-ray projection image, comprising: Provides at least a first-registered and a second-registered X-ray projection image of the patient's desired anatomical structure, wherein the first-registered and second-registered X-ray projection images show the patient's desired anatomical structure from different perspectives. At least two points of the desired anatomical structure are defined in three-dimensional space, and the three-dimensional coordinates of the at least two points are determined using the first registered X-ray projection image and the second registered X-ray projection image. Based on the determined three-dimensional coordinates of the at least two points, the scaled virtual mesh is calculated, and The calculated scaled virtual mesh is projected onto at least one of the first registered X-ray projection image and the second registered X-ray projection image and displayed to the user.

2. The method according to claim 1, in, The steps for calculating the scaled virtual mesh include: Calculate at least two control points on the line connecting the defined at least two points; For each registered X-ray projection image, calculate the cross lines. Each intersecting line intersects at a control point with the line connecting the at least two defined points. Each intersecting line is parallel to the detector, and each registered X-ray projection image is captured using the detector.

3. The method according to claim 2, wherein, Each intersecting line is perpendicular to the line connecting the defined at least two points.

4. The method according to claim 3, comprising: Calculate control points on each intersection line. The control points define the scaled virtual grid for each registered X-ray projection image.

5. The method according to claim 4, comprising: Projecting the scaled virtual grid defined by control points onto the first registered X-ray projection image and displaying it to the user, and The scaled virtual grid defined by control points is projected onto the second registered X-ray projection image and displayed to the user.

6. The method according to any one of claims 4 or 5, comprising: Calculate the distance between the at least two points in three-dimensional space, and The calculated distance is used to determine the distance between at least two control points.

7. The method of claim 6, comprising: The determined distance between the at least two control points is displayed to the user along with the at least two control points on each registered X-ray projection image.

8. The method according to any one of claims 1 to 4, comprising: Position the X-ray imaging device in six degrees of freedom. The first registered X-ray projection image and the second registered X-ray projection image provided are generated using the X-ray imaging device.

9. The method according to claim 8, in, The positioning is performed using wavy markings, optical tracking of the X-ray imaging device, the internal encoder of the X-ray imaging device, and / or other image-based markings.

10. The method according to any one of claims 1 to 4, in, The steps of defining at least two points of the desired anatomical structure in three-dimensional space include: Identify the first landmark of the desired anatomical structure in the first registered X-ray projection image. A first line is determined between the X-ray source and the X-ray detector used to generate the X-ray projection image of the first registration, on which the first landmark lies. Identify the second landmark of the desired anatomical structure in the second registered X-ray projection image. A second line is determined between the x-ray source and the x-ray detector used to generate the x-ray projection image of the second registration, on which the second landmark lies. Calculate the three-dimensional coordinates of the intersection point of the determined first line and the second line, wherein the calculated three-dimensional coordinates define the first point of the at least two points in three-dimensional space; Identify the third landmark of the desired anatomical structure in the first registered X-ray projection image. A third line is determined between the x-ray source and the x-ray detector used to generate the x-ray projection image of the first registration, on which the third landmark lies. Identify the fourth landmark of the desired anatomical structure in the second registered X-ray projection image. A fourth line is determined between the x-ray source and the x-ray detector used to generate the x-ray projection image of the second registration, on which the fourth landmark lies. Calculate the three-dimensional coordinates of the intersection point of the determined third line and the fourth line, wherein the calculated three-dimensional coordinates define the second of the at least two points in three-dimensional space.

11. The method of claim 10, comprising: Project the determined first line onto the second registered X-ray projection image, and / or The determined third line is projected onto the second registered X-ray projection image.

12. The method according to claim 11, in, The projections of the determined first line and / or the third line are used as constraints on the human-machine interface, which limit the possibility of user input for identifying landmarks in the second-registered X-ray projection image on the human-machine interface.

13. An apparatus for calculating a virtual mesh for scaling an x-ray projection image, comprising: The computing unit is configured as follows: The system receives at least a first-registered and a second-registered X-ray projection image of the patient's desired anatomical structure, wherein the first-registered and second-registered X-ray projection images show the patient's desired anatomical structure from different perspectives. At least two points are calculated in the first registered X-ray projection image and the second registered X-ray projection image, and in the desired anatomical structure, thereby determining the three-dimensional coordinates of the at least two points. Based on the determined three-dimensional coordinates of the at least two points, the scaled virtual mesh is calculated, and This causes the calculated scaled virtual grid to be projected onto at least one of the first registered X-ray projection image and the second registered X-ray projection image and displayed to the user.

14. A system for calculating a virtual mesh for scaling an x-ray projection image, comprising: The apparatus according to claim 13, and The human-machine interface is configured to display received first-registered and second-registered x-ray projection images, and to receive input signals from the user for identifying landmarks in the displayed first-registered and second-registered x-ray projection images of the desired anatomical structure.

15. The system of claim 14, comprising: An X-ray imaging apparatus, comprising an X-ray source and an X-ray detector, for generating a first-registered X-ray projection image and a second-registered X-ray projection image.

16. The system according to claim 15, wherein, The X-ray imaging device is a mobile C-arm CT.

17. A computer program product comprising a computer program that, when run on a processor or computer, causes the processor or computer to perform the method according to any one of claims 1 to 12.

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