Methods for monitoring a surgical procedure using X-ray imaging and medical X-ray system

Abstract

For reliable monitoring of interventional procedures with longitudinal implants at the lowest possible X-ray dose, a method for monitoring a surgical procedure using X-ray imaging is provided. This method employs an adjustable imaging system comprising an X-ray source and an X-ray detector. During the procedure, a pointed implant is moved forward along a movement axis with the point facing forward. The method comprises the following steps: First projection image of the implant in a first angulation; after forward movement of the implant, third projection image of the implant in a third angulation; determination of the initial position of the implant tip on the first projection image; and determination of the advanced position of the implant tip on the third projection image.Determination of a first epipolar line for the progress position of the tip in the first projection image using the epipolar geometry determined by the first and third angulations, and simultaneous display of the first and third projection images, wherein the determined epipolar line is shown in the first projection image.

Description

[0001] The invention relates to a method for monitoring a surgical procedure using X-ray imaging according to claim 1 and to a medical X-ray system for carrying out such a method according to claim 12.

[0002] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

[0003] In orthopedic and trauma surgery, screws, wires, and other implants are inserted into bone. This presents a significant challenge, as the implant must be positioned very precisely in narrow channels, depending on the patient's anatomy and the procedure to be performed, to avoid damage to surrounding tissue and ensure a successful procedure. High-quality imaging to monitor the procedure is therefore essential during implant insertion.

[0004] There are two different approaches to this, each selected depending on the complexity of the procedure. In simpler cases, a large number of 2D projection images are taken at at least two different angulations, frequently switching between angulations to gain a three-dimensional understanding of the implantation procedure relative to the patient's anatomy. In particularly complex cases, surgical navigation systems are used in combination with 3D CBCT (cone beam CT) imaging and external tracking to monitor screw insertion. In this case, an external camera system measures the relative position between the patient's anatomy and the implant using markers attached to both.

[0005] Publication US 2016 / 0 171 714 A1 discloses a registration system for registering a C-arm X-ray device for acquiring an image of an object, e.g., an interventional instrument, with a tracking system for tracking the location of the object within a field of view of the X-ray device by determining the position and shape of the object. Publication WO 2013 / 136 239 A1 discloses a graphical user interface for providing position data of an object acquired by X-ray imaging, using two images from different projection directions.

[0006] It is an object of the present invention to provide a method which simplifies the monitoring of the insertion of implants, e.g., into bones, particularly in less complex cases of surgical interventions; furthermore, it is an object of the invention to provide a medical X-ray system suitable for carrying out the method.

[0007] The object is achieved according to the invention by a method for monitoring a surgical procedure with X-ray imaging according to patent claim 1 and by a medical X-ray system according to patent claim 12. Advantageous embodiments of the invention are the subject of the respective subclaims.

[0008] The method according to the invention for monitoring a surgical intervention with X-ray imaging by means of a recording system which can be adjusted to various angulations and has an X-ray source and an X-ray detector, in which intervention in (or on) the anatomy of an examination subject an implant having a tip is moved forward along a movement axis with the tip first, comprises the following steps: recording a first projection image of the implant in a first angulation, after a forward movement of the implant recording a third projection image of the implant in a third angulation, optionally determining the original position of the tip of the implant on the first projection image, determining the advance position of the tip of the implant on the third projection image,Determining a first epipolar line for the advance position of the tip in the first projection image by means of the epipolar geometry determined by the first and third angulations, and simultaneously displaying the first and third projection images, wherein the determined epipolar line is shown in the first projection image.

[0009] This method allows the user to quickly and easily visualize the updated progress position of the implant tip in at least one additional projection image of a further angulation, or if necessary, in multiple projection images of many angulations, without additional adjustment of the imaging system. The user does not need to acquire an updated projection image for each angulation; instead, they can use the epipolar lines to update and display the progress position of the tip: using the updated third projection image, the updated progress position can be visualized in the original first projection image acquired before the movement. This method can save X-ray dose and avoid significant time and effort involved in adjusting the imaging system.At the same time, accurate and precise monitoring of a procedure with an advancing implant is possible. Overall, radiation exposure and thus the risk to the patient's health are reduced, and treatment success is maximized. The procedure enables the user to more intuitively understand the three-dimensional surgical scene. Furthermore, the simultaneous visualization of at least two or even multiple projection directions helps the user (e.g., the surgeon) assess the situation more accurately. In particular, previously unused geometric information can also be utilized. The procedure enables quasi-three-dimensional insights without the need for actual 3D imaging.

[0010] In the following, the tip of the implant is understood to be the point on the implant that is furthest forward in the direction of progression, although this does not necessarily have to be a tapered implant. It is particularly important that a "point" is used to determine the epipolar lines, i.e., not a shape that extends significantly in different directions.

[0011] Angulation refers to the projection geometry of the imaging system, i.e. the position of the X-ray source and X-ray detector as well as the projection angle of the X-ray beam (central beam) with respect to the object under examination.

[0012] It should be noted that the first angulation is different from the third angulation, otherwise epipolar geometry is not possible.

[0013] According to one embodiment of the invention, the following additional steps are carried out: recording a second projection image of the implant in a second angulation different from the first before the forward movement, determining the original position of the tip of the implant on the second projection image, determining a second epipolar line for the advanced position of the tip in the second projection image using the epipolar geometry determined by the second and third angulations, and displaying the second projection image simultaneously with the first and third projection images, with the determined second epipolar line being displayed in the second projection image. A total of three angulations are used here to provide the user with an even better overview of the procedure. The different angulations, in particular those that are as different from one another as possible, give the user a quasi-three-dimensional impression of the procedure.Difficult-to-pass areas for the forward movement of the implant can be surveyed and evaluated from different angles. This requires only two projection images with different angulations to be acquired before the implant is moved.

[0014] According to a further embodiment of the invention, the (projected) axis of movement of the forward movement of the tip of the implant is also displayed (e.g., superimposed) on the first and / or second projection image. In this way, the user can see at a glance what effect the forward movement of the implant is likely to have in the projection plane. In particular, the axis of movement is determined as an extrapolation of a longitudinal axis of the implant based on the first and / or second projection image and displayed on the first and / or second projection image. In this way, for example, the implant can be identified by segmentation and / or image recognition, and a longitudinal axis of the implant can be determined from this. This is particularly simple and quick to implement.

[0015] According to a further embodiment of the invention, the respective intersection point of the epipolar line with the movement axis (e.g., extrapolated longitudinal axis) is determined and displayed. In this way, the current progress position of the tip can be displayed very easily and clearly on the first and second projection images. This provides a quick and precise visualization of the current progress position on several (or any number of) projection images, whereby only a single current projection image is actually required.

[0016] According to one embodiment of the invention, segmentation and / or image recognition is performed on the projection images to determine the original position and / or the progress position and / or the implant. Known software algorithms can be used for this purpose.

[0017] Advantageously, for a three-dimensional impression of the forward movement of the implant, the third angulation differs from the first and second angulation.

[0018] According to one embodiment of the invention, the first, second, and third projection images are displayed side by side and / or one below the other. These can be arranged according to the user's needs to obtain an optimal overview of the procedure. Multiple display units (e.g., monitors, touchscreens, etc.) can also be used.

[0019] According to a further embodiment of the invention, the axis of movement is superimposed and / or drawn and / or marked on the projection images or otherwise visually indicated. This can also be done in color if necessary.

[0020] According to a further embodiment of the invention, at least one further projection image is recorded in the third angulation, a further advancement position of the implant tip is determined on each further projection image, further epipolar lines are determined in the first and second projection images from the epipolar geometry determined by the first and third or second and third angulations with the advancement position of the tip, and the determined further epipolar lines are displayed in the first and second projection images. In this way, any number of advancement positions of the implant tip can be visualized and the entire procedure can be optimally monitored.

[0021] The invention further comprises a medical X-ray system for carrying out the method described above, comprising an X-ray imaging device with a recording system adjustable to various angulations, comprising an X-ray source and an X-ray detector for recording X-ray images, a system control unit for controlling the medical X-ray system, an image system for analyzing the X-ray images, in particular for image recognition, an evaluation unit for determining epipolar lines, and a display unit for displaying the X-ray images and epipolar lines. Advantageously, the X-ray system comprises at least one motion and / or angle sensor and / or encoder for measuring the adjustment of the movement or rotation axes.In particular, several or all movement and rotation axes of the X-ray system are equipped with movement and angle sensors and / or encoders in order to be able to derive the extrinsics of the projection geometry.

[0022] The invention and further advantageous embodiments according to the features of the dependent claims are explained in more detail below with reference to schematically illustrated embodiments in the drawings, without thereby limiting the invention to these embodiments. They show: Fig. 1 a sequence of steps of a method for monitoring a surgical procedure using X-ray imaging; Fig. 2 shows a further sequence of steps of a method for monitoring a surgical procedure using X-ray imaging; Fig. 3 a view of the epipolar geometry when taking three projection images according to the method; Fig. 4 a view of the representation of three projection images with epipolar lines according to the method; Fig. 5 is a view of a medical X-ray system for performing the procedure; and Fig. 6 a well-known view of epipolar geometry when taking images of an object from two projection directions.

[0023] In the Fig. 1 and Fig. 2 shows steps of two embodiments of the method for monitoring a surgical procedure with X-ray imaging by means of a recording system that can be adjusted to different angulations.

[0024] The method is used, for example, to monitor a procedure on a patient in orthopedic surgery in which, for example, screws, wires or other implants are inserted into tissue and / or bone. The monitoring method makes it possible to maintain a comprehensive overview of the movement progress of the implant while simultaneously reducing X-ray exposure. After an initial acquisition from at least two different angulations, the user only needs to acquire projection images from one projection direction and can still see the progress of the implant from two or more projection directions. This makes it possible to position the implant very precisely and avoid damage to the patient's surrounding tissue during the procedure.

[0025] Monitoring is carried out by X-ray imaging using an X-ray system (e.g. in the form of a C-arm) that can be adjusted to different angulations (projection directions). The C-arm has an X-ray source and an X-ray detector. During the procedure, an implant having a front point or tip is moved forward in a straight line with the tip first along a movement axis in the anatomy of an examination object. Most implants are elongated and therefore have a clear longitudinal axis, e.g. implants such as screws, catheters, guide wires or nails. For the sake of simplicity, in many cases, e.g. in orthopedic surgery, it can be assumed that the longitudinal axis corresponds to the movement axis / advancement axis. This can be exploited in the present case. Alternatively, a movement axis can also be determined, calculated or estimated in other ways.

[0026] In the Fig. 6 shows known geometric relationships and the functionality of determining epipolar lines using general epipolar geometry: From a point-like object O and its surroundings, two different projection directions, an x-th projection center S x an x-th picture I x and a y-th projection center S y a y-th image I y recorded (e.g. with a camera). In the pictures I x and I y is the object O as x-th object projection O x and y-th object projection O y The xy epipolar plane P xy is spanned by the x-th projection center S x and the y-th projection center S y and the actual 3D position of the object O. The intersection line of the xy epipolar plane P xy with the xth picture I x forms the xth epipolar line E x and with the y-th image I yit forms the y-th epipolar line E y . Such geometric relationships are generally known from the state of the art, e.g., https: / / de.wikipedia.org / wiki / Epipolargeometrie.

[0027] The invention exploits the fact that in X-ray imaging, the spatial projection geometry is known for any angulation of an imaging system (such as a C-arm) or can be determined, for example, using sensors / encoders on the axes. Furthermore, it exploits the fact that during a rectilinear forward movement of a point, such as the tip of the implant, its movement axis can be determined or estimated and plotted in a projection image.

[0028] In a first step 10 ( Fig. 1) a first projection image I1 of the implant arranged in the examination object (e.g. body of a patient) is recorded in a first angulation - see e.g. in Fig. 3 the three-dimensional spatial relationships, where the first projection center S1 corresponds, for example, to the position of the focal point of the X-ray source 31 during the first angulation and the projection image I1 to the position of the X-ray detector during the first angulation. The acquisition of the first projection image can, for example, be carried out before the start of the forward movement of the implant to be monitored. For example, in a procedure in which an implant (e.g. screw) is to be inserted into the bone, the implant can have been previously positioned on the cortical bone (bone cortex) as the starting position for traversing the bone, and the axis of movement can have been fixed (not part of the procedure). The acquisition system (C-arm) can be aligned based on the desired axis of movement of the implant for the acquisition of the first projection image.

[0029] The first projection image I1 shows in particular the implant 20 and the tip 21 of the implant, whereby the position of the tip 21 is referred to here as the original position.

[0030] After the implant and its tip have been advanced, a third projection image I3 of the implant is acquired in a second step 11, using a third angulation of the imaging system, which differs from the first angulation. The third projection image I3 also depicts the implant 20 and the tip 21 of the implant, with the tip 21 in a progress position (i.e., after the advancement has been completed). Fig. 3 shows the three-dimensional spatial relationships, the third projection center S3 used for this purpose, which corresponds to the position of the focal point of the X-ray source 31 at the third angulation, and the projection image I3, which corresponds to the position of the X-ray detector at the third angulation.

[0031] In a third, optional step 12, the original position of the tip of the implant is determined on the first projection image I1, e.g., using segmentation or image recognition software running on an imaging system. Image recognition methods of this type are well known. In addition, the implant (if imaged) can also be fully recognized, e.g., in order to determine or estimate its longitudinal axis. The third step 12 can also be performed at a different time, e.g., directly after the image has been taken. In a fourth step 13, the advance position of the tip of the implant (optionally also the implant) is determined on the third projection image I3. This can also be performed using known segmentation or image recognition software on the imaging system.

[0032] In a fifth step 14, using the known projection geometry of the first and third angulations - as in Fig. 3 - a first epipolar line E1 on the first projection image I1 determines which first epipolar line E1 represents the projection of the tip's advancement position determined from the third projection image onto the first projection image I1. The first epipolar line E1 is created by projecting the spatially arranged connecting line H3 between the third projection center S3 and the advancement position of the implant's tip onto the first projection image I1.

[0033] In a sixth step 15, the first projection image I1 and the third projection image I3 are displayed, for example, on a display unit or a screen, e.g., as a split screen, with the first epipolar line E1 being depicted in the first projection image I1, e.g., faded in, superimposed, drawn in, etc. The projection images can be shown, for example, side by side and / or one above the other. The display is such that the user receives a particularly good overview of the procedure. Fig. Figure 4 shows an example of such a display, wherein in addition to the first projection image I1 and the third projection image I3, a second projection image I2 (to be discussed further below) is shown.

[0034] In a seventh step 16, the predicted movement axis A1 of the tip of the implant is shown on the first projection image I1, e.g. faded in, superimposed or drawn in - see Fig. 3 and Fig. 4. For this purpose, the movement axis A1 is determined in advance, e.g., calculated or estimated. The movement axis A1 of the tip of the implant on the first projection image I1 can be determined, for example, as an extension or extrapolation of the longitudinal axis of the implant 20 (or its projection onto the first projection image I1). In an eighth step 17, the progress position P is then determined from the intersection point of the movement axis A1 and the first epipolar line E1 on the first projection image I1. F1 the tip of the implant on the first projection image I1.

[0035] In the Fig. 2 shows a further method, wherein instead of the first step 10, in a ninth step 100, before the forward movement of the implant, a first projection image I1 in a first angulation and a second projection image I2 in a second angulation are recorded, wherein the two angulations differ. In particular, significantly different angulations can be used to obtain the most comprehensive overview possible. In further embodiments (not shown), a plurality of projection images with many different angulations can also be recorded, depending on how many views the user desires. The second step 11 in Fig. 2 corresponds to the procedure in Fig. 1.

[0036] Instead of the third step 12, the initial position of the implant tip is optionally determined in a tenth step 120 on the first projection image I1 and on the second projection image I2 (alternatively also on further projection images), again for example, using segmentation or image recognition software. The fourth step 13 in Fig. 2 corresponds to the procedure in Fig. 1.

[0037] Instead of the fifth step 14, in an eleventh step 140, using the known projection geometry of the first and third angulations, a first epipolar line E1 is determined on the first projection image I1, which first epipolar line E1 represents the projection of the advance position of the tip determined from the third projection image onto the first projection image I1; and additionally, using the known projection geometry of the second and third angulations, a second epipolar line E2 is determined on the second projection image I2, which second epipolar line E2 represents the projection of the advance position of the tip determined from the third projection image onto the second projection image I2.The first epipolar line E1 is created by projecting the spatial connecting line H3 between the third projection center S3 and the advance position of the tip of the implant onto the first projection image I1, and the second epipolar line E2 is created by projecting the spatial connecting line H3 between the third projection center S3 and the advance position of the tip of the implant onto the second projection image I2.

[0038] Alternatively, additional epipolar lines can be determined on additional projection images.

[0039] Instead of the sixth step 15, the first projection image I1, the second projection image I2 and the third projection image I3 are subsequently displayed in a twelfth step 150, for example, on a display unit or a display, wherein the first epipolar line E1 is depicted in the first projection image I1 and the second epipolar line E2 is depicted in the second projection image I2, for example, faded in, superimposed, drawn in, etc. - see Fig. 3. The projection images can be shown side by side and / or on top of each other - see Fig. 4. If necessary, many projection images can also be displayed.

[0040] Instead of the seventh step 16, in a thirteenth step 160 the movement axis A1 of the tip of the implant is shown on the first projection image I1 and the movement axis A2 of the tip of the implant is shown on the second projection image I2, e.g. faded in, superimposed or drawn in - see Fig. 3 and Fig. 4. For this purpose, the axes of motion A1 and A2 are determined in advance, e.g., calculated or estimated. The axes of motion can be determined, for example, as extensions or extrapolations of the longitudinal axis of implant 20 (or as a corresponding projection).

[0041] In a fourteenth step 170, the intersection point of the movement axis A1 and the first epipolar line E1 on the first projection image I1 results in the progress position P F1 the tip of the implant on the first projection image I1 and from the intersection of the movement axis A2 and the second epipolar line E2 on the second projection image I2 the progress position P F2 the tip of the implant on the second projection image I2 - see Fig. 4.

[0042] Overall, the order of the steps can also be varied.

[0043] To visualize further forward movement of the implant during the procedure, the procedure or the acquisition of updated projection images with further updated advance positions of the tip and corresponding determinations and representations of epipolar lines can be repeated as often as required. In this way, the entire procedure or the entire advance movement can be visualized step by step. The display can then show the current projection image together with the projection images acquired before the advance movement, and the latter can show the respective current advance position with the current epipolar lines. The movement axes can be retained, so that the further updated advance positions are again determined by the intersection points.

[0044] The superimposition of the epipolar lines and the motion axes provides the user with valuable additional information that approximates a three-dimensional representation. The implant's progress, for example, in bone or tissue, can be constantly monitored. Since the direction of the motion axis remains constant, the updated progress position of the tip can be visualized on a variety of projection images, enabling a more intuitive understanding of the three-dimensional surgical scene.

[0045] The procedure saves time and patient dose, as old projection images from other angulations do not need to be updated, yet the current progress position of the implant tip can still be displayed. Furthermore, the simultaneous visualization of multiple projection directions helps the user assess the situation accurately and reliably. In particular, the proposed overlay utilizes previously unused geometric information. The main difference between the procedure and navigation-based solutions is its independence from 3D imaging and external tracking systems. The procedure is simple, inexpensive, requires little hardware, and saves time and X-ray dose.

[0046] In Fig.5 shows a medical X-ray system 38 for carrying out the method. It has, for example, a recording system in the form of a C-arm 30 with an X-ray source 31 and an X-ray detector 32, which C-arm 30 can be adjusted to a variety of angulations. The medical X-ray system 38 is controlled by a system controller 33, for example to carry out the method and to record projection images. In addition, the medical X-ray system 38 has an imaging system 35 which is designed to process projection images, in particular with software for segmentation and / or image recognition. The imaging system 33 or the corresponding software can recognize objects such as an implant and its tip in the projection images. In addition, an evaluation unit 36 ​​is provided for determining epipolar lines, wherein the corresponding information, e.g., regarding the angulations, is supplied by the system controller.A display unit 34 is also provided for displaying the X-ray images, the determined epipolar lines, and the extrapolated motion axes. The medical X-ray system 38 may also include a storage unit 37.

[0047] Such a medical X-ray system 38 for performing the procedure can be formed, for example, by a mobile C-arm X-ray device. For precise determination of the angulations (position / orientation of the X-ray source and X-ray detector) or the entire epipolar geometry, encoder information from the motion axes of the imaging system can be read and used. External sensors can also be used for position determination. The procedure uses such known C-arm positions to generate the corresponding visualization on the projection images.

[0048] The invention can be briefly summarized as follows: For reliable monitoring of interventional procedures with longitudinal implants with the lowest possible X-ray dose, a method is provided for monitoring a surgical procedure with X-ray imaging by means of a recording system that can be adjusted to various angulations, comprising an X-ray source and an X-ray detector, in which procedure in the anatomy of an examination subject an implant having a tip is moved forward along a movement axis with the tip first, with the following steps: recording a first projection image of the implant in a first angulation, after a forward movement of the implant recording a third projection image of the implant in a third angulation, determining the original position of the tip of the implant on the first projection image,Determining the advancement position of the tip of the implant on the third projection image, determining a first epipolar line for the advancement position of the tip in the first projection image using the epipolar geometry determined by the first and third angulations, and simultaneously displaying the first and third projection images, wherein the determined epipolar line is shown in the first projection image.

Claims

[1] Method for monitoring a surgical procedure with X-ray imaging by means of a recording system which can be adjusted to various angulations and which has an X-ray source and an X-ray detector, in which procedure in the anatomy of an examination subject an implant having a tip is moved forward along a movement axis with the tip first, comprising the following steps: • Recording a first projection image of the implant in a first angulation, • After a forward movement of the implant, a third projection image of the implant is taken in a third angulation, • (Optional) Determination of the original position of the tip of the implant on the first projection image, • Determination of the advancement position of the tip of the implant on the third projection image, • Determination of a first epipolar line for the advance position of the tip in the first projection image using the epipolar geometry determined by the first and third angulation, and • Simultaneous display of the first and third projection images, with the determined epipolar line shown in the first projection image. [2] A method according to claim 1, comprising the additional steps of: • Recording a second projection image of the implant in a second angulation different from the first before the forward movement, • Determination of the original position of the tip of the implant on the second projection image, • Determination of a second epipolar line for the advance position of the tip in the second projection image using the epipolar geometry determined by the second and third angulation, and • Displaying the second projection image simultaneously with the first and third projection images and displaying the determined second epipolar line in the second projection image. [3] Method according to claim 1 or 2, wherein the (projected) axis of movement of the forward movement of the tip of the implant is further displayed on the first and / or the second projection image. [4] The method of claim 3, wherein the axis of movement is determined as an extrapolation of a longitudinal axis of the instrument and is displayed on the first and / or second projection image. [5] Method according to claim 4, wherein the respective intersection point of the epipolar line with the movement axis is determined and displayed. [6] Method according to one of the preceding claims, wherein image recognition is carried out for determining the original position and / or the progress position and / or the implant on the projection images. [7] The method of claim 2, wherein the third angulation is different from the first and second angulations. [8] A method according to any one of claims 1 to 6, wherein the third angulation is equal to the first or second angulation. [9] Method according to one of the preceding claims, wherein the first, second and / or third projection images are displayed side by side and / or one below the other. [10] Method according to one of the preceding claims, wherein the movement axis is superimposed and / or drawn and / or marked on the projection images. [11] Method according to claim 2, wherein at least one further projection image is recorded in the third angulation, a further progress position of the tip of the implant is determined on the further projection image, further epipolar lines are determined in the first and the second projection image from the epipolar geometry determined by the first and third or second and third angulation with the progress position of the tip, and the determined further epipolar lines are displayed in the first and the second projection image. [12] Medical X-ray system (38) for carrying out a method according to one of claims 1 to 11, comprising • an X-ray imaging device with a recording system (30) adjustable in various angulations, comprising an X-ray source (31) and an X-ray detector (32) for recording X-ray images, • a system control unit (33) for controlling the medical X-ray system, • an image system (35) for analyzing the X-ray images, in particular for image recognition, • an evaluation unit (36) for determining epipolar lines, and • a display unit (43) for displaying the X-ray images and epipolar lines.

Images