Method and imaging system for image localization of surgical effectors using C-arm characterization parameters

Abstract

A method for obtaining radiographic images of anatomical features and surgical effectors in a patient's surgical space involves detecting a specific posture of a particular C-arm used to obtain radiographic images of the surgical space. Characterization parameters for a specific C-arm in a particular posture are determined and incorporated into an equation implemented in imaging software that works to produce images of anatomical features and surgical effectors in the surgical space. Once a live radiographic image of the surgical space is obtained, the imaging software produces live images of anatomical features and surgical effectors as a function of the characterization parameters to account for possible deviations resulting from the C-arm posture. Alternatively, possible errors in the imaging process can be visualized or automatically detected.

Description

[Technical Field]

[0001]

[0001] This application claims priority to the ongoing U.S. application No. 18 / 314444, filed on 9 May 2023, titled "Imaging System and Method for Image Localization of Surgical Effectors Using C-Arm Characterization Parameters," the entire disclosure of which is incorporated herein by reference. [Background technology]

[0002]

[0002] A typical imaging system 100 is shown in Figure 1. This imaging system includes a base unit 102 that supports a C-arm imaging device 103. The exemplary C-arm, shown in detail in Figure 2, includes a radiation source 104, which is positioned below the patient P and directs a radiation beam to an upper receiver 105. It is known that the radiation beam emitted from the source 104 is cone-shaped, and therefore the field of exposure can be changed by moving the source closer to or further away from the patient. The source 104 may include a collimator configured to limit the field of exposure. The C-arm 103 can be rotated around the patient P in the direction of arrow 108 for various observation angles of the surgical site. In some cases, effectors made of metal or radiopaque material, such as implants or instruments T, may be placed at the surgical site, and it may be necessary to change the observation angle so that the view of the site is not obstructed. Thus, the position of the receiver relative to the patient, and more specifically, relative to the surgical site of the object, may be changed during the procedure as required by the surgeon or C-arm technician. Accordingly, the receiver 105 may include a tracking target 106 (Figure 1) attached thereto, which allows tracking of the C-arm's position using a localizer system or tracking device 130. For example, the tracking target 106 may include several infrared emitters spaced apart around the target, and the tracking device is configured to triangulate the position of the receiver 105 from the infrared signals emitted from its elements. The base unit 102 includes a control panel 110 through which a radiologist can control the C-arm's position and radiation exposure. Thus, a typical control panel 110 allows the technician to "take pictures" of the surgical site, control the radiation dose, and initiate pulsed radiation imaging when instructed by the surgeon.

[0003]

[0003] The receiver 105 of the C-arm 103 sends image data to the image processing device 122. The image processing device may include associated digital memory and a processor for executing digital and software instructions. The image processing device may also incorporate a frame grabber, which uses frame grabber technology to produce digital or pixel-based images for projection as displays 123, 124 on a display device or graphical interface 126. The displays are positioned so that the surgeon can view them interactively during the procedure. The two displays may be used to show images from two perspectives, such as lateral and AP, and may also show baseline and current scans of the surgical site. An input device 125, such as a keyboard or touchscreen, may allow the surgeon to select and manipulate images on the screen. It is understood that the input device may incorporate an array of keys or touchscreen icons corresponding to various tasks and features implemented by the image processing device 122. The image processing device includes a processor that converts the image data received from receiver 105 into a digital format. In some cases, the C-arm can operate in cinematic exposure mode, producing many images per second. In those cases, motion artifacts and noise can be reduced by combining and averaging a large number of images over a short period of time into a single image.

[0004]

[0004] Standard X-ray guided surgery typically involves repeatedly taking X-ray images of the same or similar anatomical structures as the effector (e.g., screws, cannulas, guidewires, instruments, etc.) is advanced into the body. This process of moving the effector and obtaining images is repeated until the desired position of the instrument is achieved. This repeated process alone can increase a patient's lifetime risk of cancer by more than 1% after a single strong X-ray intervention.

[0005]

[0005] Conventional image-guided surgery ("IGS") uses previous imaging as a roadmap, projecting a virtual representation of the effector onto a virtual representation of the anatomical structure. As the instrument moves within the body, the representation of the effector is displayed on a computer monitor to help pinpoint its location. The goal is to eliminate the need for X-ray imaging. Unfortunately, in reality, the reality of these devices does not meet this desire. They typically require considerable preparation time, which not only limits their adoption for long surgeries but also makes them impractical. They become increasingly inaccurate over time as drift and patient movement disrupt the relationship between physical and virtual space. Typical IGS techniques often significantly alter the workflow and do not provide physicians with the ability to see what is happening in real time and adjust instruments as needed, which is the main reason why fluoroscopy is used.

[0006]

[0006] A great benefit to the medical community would be a simple image localizer system that assists in locating instruments without altering the workflow. It would be substantially beneficial if the system could be quickly prepared and operated and be practical for all types of medical interventions, both rapid and prolonged. The desirable system would greatly limit the number of X-ray images taken, but would not require them to be removed. Thus, by both encouraging re-imaging and using it as a means of readjustment, the system would ensure that the procedure proceeds as planned and desired. By using actual X-ray representations rather than virtual representations of effectors, accuracy would be further increased and the need for computer-human interaction would be minimized. If the system mimics live fluoroscopy between images, it would help in locating instruments without giving substantial radiation and would also provide the accuracy of live imaging. [Overview of the Initiative]

[0007]

[0008] According to one configuration of the present disclosure, a method is provided for obtaining an X-ray image of an anatomical structure and a surgical effector in a patient's surgical space, wherein the image is adjusted based on an imaging device or C-arm characterization parameters. The method includes detecting the position of one or more surgical effectors in the surgical space, generating positional data therefor, and detecting the posture of a particular C-arm to obtain a live X-ray image of the surgical space. The particular C-arm includes an X-ray emitter and an X-ray detector, the detector including an array of multiple pixels that can be actuated by an X-ray cone beam emitted from the emitter.

[0008]

[0009] In one step of the method, characterization parameters for a specific C-arm in a particular posture are determined, and these characterization parameters are incorporated into one or more equations implemented in imaging software used to create images of anatomical features and surgical effectors in the surgical space detected by the specific C-arm. The images are represented by pixels of a detector actuated by an X-ray beam, and the position of the pixels is determined by one or more equations as a function of positional data and the characterization parameters of a specific C-arm in a particular posture. The characterization parameters include multiple parameters that are unique to a particular C-arm and depend on the posture of the C-arm. One or more equations can be used to determine the position of pixels corresponding to anatomical features and surgical effectors detected by an X-ray cone beam in the surgical space.

[0009]

[0010] After obtaining live X-ray images of the surgical space, imaging software is operated to create live images of anatomical features and surgical effectors in the surgical space, based on the position of pixels actuated by an X-ray cone beam, determined by one or more equations as a function of characterization parameters. This live image is then displayed for use by the surgeon during the surgical procedure.

[0010]

[0011] According to another configuration of this disclosure, a method for producing a display of images of the internal anatomical structures of a patient and one or more radiopaque effectors in the surgical field during a medical procedure includes: obtaining a baseline image of the surgical field including the patient's anatomical structures; obtaining images of radiopaque effectors in the surgical field independently of the baseline image using a C-arm; and then displaying a superimposed image including images of radiopaque effectors superimposed on the baseline image of the surgical field, such that the images of the radiopaque effectors are positioned relative to images of the patient's anatomical structures in the same manner that the actual radiopaque effectors are positioned relative to actual anatomical structures. In a further step of the method, the position and motion of the radiopaque effectors are tracked, and in the superimposed image, the images of the radiopaque effectors are moved according to the tracked motion of the radiopaque effectors.

[0011]

[0012] In one configuration of the present disclosure, the method further includes determining the position of an X-ray detector and the position of a radiopaque effector relative to the position of the X-ray detector using tracking information from a tracking system. A tip mark is displayed in the superimposed image, and the tip mark corresponds to the position of the tip of the radiopaque effector relative to the position of the X-ray detector in the superimposed image. The tip mark can be used to visually detect errors in the imaging system if the position of the tip mark in the superimposed image is not aligned with the tip of the radiopaque effector in the superimposed image. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a three-dimensional view of an image-guided surgical setting, including an imaging system, image processing devices, and localizers or tracking devices for surgical instruments and devices. [Figure 2]Figure 2 is a perspective view of a conventional C-arm X-ray device, with the system coordinates superimposed on it. [Figure 3] Figures 3A-3D are screenshots of the surgical site, showing the patient's anatomical structure and the movement of the radiopaque effector in relation to a fixed image of the surgical site. [Figure 4] Figure 4 shows the steps involved in displaying the tracked effector movement in an X-ray image of the surgical site. [Figure 5] Figure 5 is an X-ray image of a surgical site including a tool having a chevron shape according to the present disclosure. [Figure 6] Figure 6 is a magnified X-ray image of the working end of a tool with a chevron shape. [Figure 7] Figure 7 is a perspective view of the X-ray detector shown in Figure 2, with the adjustment collar attached. [Figure 8] Figure 8 is a bottom view of the adjustment collar shown in Figure 7. [Figure 9] Figure 9 is a perspective view of the X-ray source for the C-arm device shown in Figure 2, along with the source adjustment device attached to it. [Figure 10] Figure 10 is a top view of the source adjustment device shown in Figure 9. [Modes for carrying out the invention]

[0013]

[0025] A computer-assisted imaging localization system is disclosed in U.S. Patent No. 104441367 ('367 Patent), which assists physicians in locating implants and instruments within a patient's body. The disclosure of this '367 Patent is incorporated herein by reference. The system has the desired effect of displaying actual instruments or implants without requiring direct interaction with a computer, and using this displayed image to guide surgery. To do this, the system displays and moves overlapping images on a computer screen, allowing one image to be seen through another. These image “masks” can be unaltered images or images that have been manipulated to enhance or soften the anatomical or non-anatomical features of the image. By sliding these images over each other, it is possible to assist in locating medical devices with high accuracy using a limited number of additional X-rays.

[0014]

[0026] As described in the 367 patent, an initial X-ray image of the surgical site is obtained as a “localizing shot” or “baseline image.” The image processing device 122 creates a digital image that can be digitally displayed and manipulated. Once the anatomical structure is identified and displayed on a computer screen, a “new” image with an effector or instrument T is acquired, which is also converted into a digital image by the image processing device 122. This new image is displayed on top of the original localizing shot, so that the resulting image looks like a conventional image on a fluoroscopy screen. The effector T incorporates a reference or marker, which is trackable by a localizer system 130 that can track the movement of the effector. As illustrated in the image in Figure 3A-3D, the 3D movement of the effector, measured by the localizer system, can be applied to the digital representation of the “new” image in relation to moving the “new” image relative to the “localizing shot” image. Therefore, as the tip of the effector is tracked, the movement of the "new" image shows the change in the position of the instrument tip being tracked in relation to the stationary anatomical structure represented in the "localizing shot." Thus, on the computer screen, it appears as if a live fluoroscopy is being performed because the effector is being moved, and as if an actual tool or implant is being moved and adjusted in relation to the patient's anatomical structure. When the next image is acquired, the tip of the effector is in the position desired by the physician.

[0015]

[0027] In the example shown in FIGS. 3A - D, after an initial "localizing shot", a tracked bone screw 10 is inserted into the patient and projected onto a display 122 / 123 (FIG. 1) as in the screen shot of FIG. 3A. As represented in the screen shot of FIG. 3B, when the tracked instrument 10 moves outside the field of the localizing shot or baseline image 12, two overlapping images can be identified, with the localizing shot 12 appearing on the left and the new low - radiation image 14 appearing on the right. When the tracked screw is moved to an ideal position based on the physician's desire, as shown in the screen shot of FIG. 3C, the images on the screen can always project an overlay image (overlaying the full - dose localizing shot 12 and the low - radiation image 14), which replicates something similar to what a new fluoroscopic diagnostic image would look like at any point and mimics fluoroscopic diagnosis in real - time without obtaining a new live image. It can be understood that the localizing or baseline image 12 does not change as long as at least the C - arm or X - ray source is not moved, even if the effector 10 moves. Thus, the digital data regarding the localizing image 12 is not manipulated by the image - processing device during the movement of the effector. On the other hand, since the image - processing device manipulates the digital data of the "new" image based on the projected movement of the tracked effector, the "new" image moves across the display as the effector moves. It can be understood that the "new" image can be used as a new baseline image and that even a new image can be overlaid on top of it. Also, it can be understood that the "new" image does not have to be a low - radiation image.

[0016]

[0028] To confirm that the effector 10 is in the desired position by the physician, a new image of the static total radiation dose can be acquired, such as the display in the screen shot of FIG. 3D. If the alignment of the image is misaligned for some reason or further fine adjustment is required, this newly obtained image can be replaced with the previous localization shot image as the baseline image, and the process is repeated. Therefore, the system resets or readjusts when a new image of the total radiation dose is acquired, so that subsequent images are always displayed more accurately than the previous ones. Since the readjustment process can be made independent of the radiation dose of the image, it is considered that the readjusted image can be less than the total radiation dose image.

[0017]

[0029] When the physician moves the effector 10, the "new" image moves with the effector, and the image can be a low radiation dose image if desired. As shown in FIG. 3C, when the effector is within the field of the baseline or localization shot image, the image of the effector from the low radiation dose image is combined with the static localization image, so that the physician can clearly see the patient's anatomical structure and the position of the effector associated with that anatomical structure. When the effector is moved within the field of the baseline image, the image of the effector (and the "new" image) moves accordingly, so that the physician can guide the tip of the effector to the desired position within the anatomical structure. The movement of the "new" image on the display is based on the geometry of the tip of the effector associated with the position within the cone beam of fluoroscopy. The position of the effector / instrument T can be readjusted in each new X-ray shot. On the instrument side, this means that each X-ray exposure resets the relative position or initial starting point of the "new" image to the current position of the effector being tracked, and the "new" image in which the effector is located is linked to the effector being tracked.

[0018]

[0030] The movement of the "new" image on the display is based on the geometry of the effector tip relative to its position within the cone beam of the fluoroscopy system, as shown in Figure 4. With respect to the same relative motion, the closer the tracked effector tip is to the X-ray source, the greater the movement of the effector projection (in terms of pixels) relative to the size of the "new" image, and therefore the "localizing shot." Assuming a standard-sized image, such as a 9-inch image intensifier, and a typical distance of 1000 mm from the intensifier to the X-ray source, there is a movement of approximately 2.24 pixels / mm of the tracked effector projected onto the image intensifier. As shown in Figure 4, as you move away from the image intensifier and closer to the source, this ratio of pixels / mm movement increases steadily. Specifically, the motion distance of the projection of the tracked effector in the image intensifier is given by Y' = X' * Y / X, where Y is the actual motion distance of the effector, X is the distance from the source to the tracked effector / instrument, X' is the distance from the source to the localized image in the image intensifier, and Y' is the projected motion distance. It can be understood that the distance X' is typically fixed through treatment of the conventional C-arm X-ray source. The distance X and motion distance Y can be determined by the image processing device 122 (Figure 1) based on data received from the localizer system used to track the motion of the effector. The image processing device uses the projected motion distance Y to move a "new" image on the display accordingly.

[0019]

[0031] It is important to understand that obtaining the most accurate possible X-ray images of the surgical site and effector is crucial. Furthermore, it is important that the X-ray images are registered to an established reference system fixed in relation to the patient, so that the movement of the surgical effector is accurately represented on the display used by the surgeon to guide the effector. As is known, the receiver or detector 105 of the C-arm includes an array of pixels actuated by the X-ray beam generated by the source 104. Thus, the pixels have a fixed position in relation to the established reference system, i.e., the C-arm, and therefore the physical position of the object detected by the X-ray can be established in the displayed image based on the position of the actuated pixels. However, each X-ray device has its own unique characteristics, which can cause the acquired image to deviate from the actual anatomical structure and effector geometry, such as image distortion or twisting. Therefore, it is important that the imaging device or C-arm be adjustable so that the pixels (and, depending on the nature of the image, the voxels) of the X-ray image can be corrected as needed.

[0020]

[0032] The imaging system of this disclosure is intended to provide clear communication to the surgeon when the imaging system and the navigation system are not synchronized. The accuracy of the image guidance system during any surgical procedure may decrease over time. Errors of this nature may include the actual anatomical structure losing its relevance to the imaging data set when the anatomical structure moves relative to a fixed reference with respect to the C-arm and the navigation system, i.e., when the patient's position shifts on the OR table. Other errors may occur when the reference system is shifted, such as by bumping into the C-arm. Errors in the adjustment of the imaging system and the navigation system are also a source of discrepancy between the actual surgical site and the representation of the surgical site shown to the surgeon to assist and guide the medical procedure. In conventional image guidance systems, the only way to confirm the continued accuracy of the system was to place the instrument on a known anatomical feature or reference structure and verify that the system accurately represented the instrument's position on the X-ray. However, in those conventional systems, there is nothing to prompt accuracy confirmation other than the surgeon's intuition, a planned accuracy confirmation protocol, or the visual appearance of an obvious error.

[0021]

[0033] One feature of this imaging system is that it provides a means for the surgeon to identify when the system accuracy begins to deteriorate. According to this system, the position and trajectory of an instrument or effector in the surgical field are superimposed on an X-ray image of the surgical site. As described above, the instrument or effector T incorporates a reference or marker, which is trackable by a localizer system 130 that can track the movement of the effector. Thus, the 3D position and orientation of the effector T are known. Similarly, the 3D position of the X-ray image can be obtained by the localizer system or other tracking devices. For example, as will be described in detail later, a calibration collar 150 can be attached to the detector housing of the C-arm, with the reference located on the housing and detectable by the localizer system 130. With this information, the imaging system of this disclosure "knows" the position and orientation of the effector T in the X-ray image.

[0022]

[0034] As shown in Figure 5, the imaging system generates a marker 200 indicating the position of the tip of the instrument or effector in use, based on tracking information. The trajectory of the effector is represented by another marker, such as a series of dots 201 extending from the tip marker, as shown in Figure 5. These markers 200, 201 appear in the X-ray image presented to the surgeon. As described above, this X-ray image includes an image or representation of the instrument or effector T and the working tip W of the effector superimposed on an image of an anatomical structure, and as the physical effector is moved by the surgeon, the image of the effector moves. As shown in Figure 5, the working tip W and the marker 200 are not aligned, and the trajectory marker 201 is not aligned with the trajectory of the image of the effector T. In this case, the surgeon immediately recognizes that the tracking and imaging features are not synchronized or properly aligned.

[0023]

[0035] On the other hand, as shown in Figure 6, proper adjustment can be demonstrated when the tip mark 200 is directed towards the working tip of the effector image and the trajectory mark 201 is aligned with the longitudinal axis of the effector T. In the exemplary embodiment, the tip mark 200 is chevron-shaped to enhance the visibility of the mark superimposed on the X-ray image. The trajectory mark 201 can be a solid dot that is easily visible but does not obstruct the view of the underlying anatomical structure.

[0024]

[0036] During the procedure, the surgeon moves the effector in relation to the surgical site. As described in the '367 patent, a localizer or tracking system tracks the movement of the effector, and imaging software translates the movement in the tracking system coordinate system to the equivalent movement in the C-arm coordinate system, and ultimately to the movement in the resulting X-ray image. As described above, this movement is visually captured by overlaying an image of the surgical site with the effector onto a baseline image. As the effector moves, the localizer tracks its movement, and the imaging system moves the overlaid markers 200, 201 accordingly. In a properly tuned system, the movement of the markers and the effector T in the overlaid image coincides, and therefore the tip marker 200 follows the movement of the working tip W of the effector T. Any loss of correlation between the X-ray images of the markers and the effector will indicate a problem. Therefore, labels 200 and 201 provide the surgeon or C-arm operator with a clear visual signal that there is a discrepancy in the imaging system and / or tracking system.

[0025]

[0037] If the marker and the working tip do not align, the first response may be to take a new X-ray of the surgical site. If the apparent lack of alignment is due to patient or reference system movement, the new X-ray will realign the image with the actual patient's anatomical structure. In this case, there is no alignment error between tracking and imaging, so only the X-ray image needs to be re-registered against the actual anatomical structure. If the marker and the working tip still do not align, the system can stop tracking the effector and alert the surgeon.

[0026]

[0038] As described above, labels 200 and 201 provide the surgeon with a visual indication of whether the imaging system and / or tracking system are properly calibrated. The goal is to ensure that the position and orientation of the surgical effector in superimposed X-ray images related to anatomical structures are correct and within at least an acceptable margin, such as 2-3 mm.

[0027]

[0039] Another approach allows for the detection and location of the working tip of an effector image in an X-ray image within a C-arm coordinate system. One approach for determining the location of the working tip of an effector in an X-ray image is described in patent '367, which is incorporated herein by reference. This approach relies on the analysis of pixels in an X-ray image to identify radiopaque features such as surgical effectors. Imaging software can isolate the radiopaque feature based on the position of the detector array pixels corresponding to the tip in the detector array, and then determine the position of the tip in a C-arm coordinate system. Since the position of each pixel in the detector array in the C-arm coordinate system is known, the position of the tip in the C-arm coordinate system is known. The actual physical tip of the effector can be detected by a localizer or tracking system, as described above, and its position in the C-arm coordinate system can be derived from the tracking system data. Two coordinates are created: one corresponding to the position of the tip in the X-ray image, and the other corresponding to the expected position of the tip relative to the actual physical position of the effector. These coordinates are compared, and if they deviate by a predetermined amount, the imaging software can create a warning state, which may include issuing a warning and / or initiating diagnostic and / or corrective actions to isolate and correct the source of the error if possible. As suggested above, the range of deviation can be 2-3 mm before the error is identified.

[0028]

[0040] It can be understood that the markers 200, 201 and methods described above can be used to determine whether the position of the effector tip derived from the registered navigation information is synchronized with the actual position of the tip in the new X-ray image. The navigation information can provide the position of the tip determined by the localizer. The tip detection software described above can determine the position of the effector tip in the new X-ray image and can also highlight the appearance of the tip in the imaging information for the new X-ray image. The markers 200, 201 determined by the navigation or tracking software can be overlaid on the new X-ray image to give the surgeon immediate indication of whether the navigation information is synchronized with the imaging information. Alternatively, the pixel position of the tip created from the navigation information can be compared with the pixel position of the tip created by the tip detection software applied to the new X-ray image. If the deviation between pixel positions is within a desirable range, the system can provide notification to the surgeon. Alternatively, if the deviation exceeds a desirable range, the system can issue a warning and / or initiate a diagnosis and / or take corrective action.

[0029]

[0041] C-arm adjustment can be achieved using an adjustment collar 150 (Figure 7) configured to be attached to the detector housing HD of the C-arm, the end face 151 of this collar being flush with the end face of the housing. The end face 151 contains several unique glyphs 152a-152g detectable by the receiver 105, as shown in Figure 8. The glyphs are positioned around the periphery of the collar so that they do not interfere with the image of the surgical site. The glyphs can be metal rods detectable by X-ray. The 3D position of each glyph relative to the C-arm is fixed and known.

[0030]

[0042] Furthermore, the C-arm adjustment process involves adjusting the X-ray source, which is performed separately from or together with the detector adjustment. For this purpose, a source cap 180 is provided, which is located in the C-arm housing H as shown in Figure 9. D It is configured to be mounted on top of the source housing H. This cap includes a U-shaped body 182, which is the source housing H. S It is sized to be mounted on the output surface. The U-shaped body 182 includes an adjustment plate 190 (Figure 10), which is located on the source housing H S It is mounted co-plane with the output surface. This plate defines the beam transmission path to the X-ray detector of the C-arm device and the aligned aperture 191. The plate further defines a plurality of glyphs 192a-g extending radially into the aperture 191, thereby intersecting the beam delivered by the X-ray source. Like glyph 152, glyph 192 is X-ray detectable. Furthermore, the 3D position of each glyph on the source cap relative to the C-arm is fixed and known. Thus, given the motion and position of the C-arm, the expected orientation and position of the two sets of glyphs 152 and 192 are known. Details of the adjustment collar, source cap, and glyphs are disclosed in U.S. Patent No. 10825177 ('177 Patent), issued November 3, 2020, which is incorporated herein by reference.

[0031]

[0043] In one configuration of this disclosure, the glyphs can be made of a less radiopaque material so that they appear in the X-ray image only when imaging very low-density materials (such as air or plastic), and are invisible in the X-ray image when imaging highly radiopaque materials (such as human anatomical structures or surgical effectors). This feature allows the collar and cap to be fixed to the C-arm at all times rather than being removed before live procedures. Alternatively, the glyphs can be replaced with holes / gaps in the material of the collar / cap. These holes / gaps would appear as bright objects that can still be identified as radiopaque glyphs for characterization purposes.

[0032]

[0044] The C-arm, and / or adjustment collar and source cap, are equipped with references or markers such as tracking targets 106 (Figure 1) detectable by the localizer system or tracking device 130. (It is conceivable that the system components, and other forms of detection, can be implemented to enable accurate tracking of surgical instruments and implants at the surgical site.) Thus, the spatial position and orientation of the C-arm can be known when an X-ray image is obtained. The image processing device 122 is configured to identify glyphs 152 on the adjustment collar 150 and glyphs 192 on the source cap 180 in the X-ray image in order to adjust the C-arm. Specifically, the processing device runs software that finds the pixel positions in the X-ray detector pixel array of the receiver 105 that correspond to the metal rods and / or beads that form the glyphs.

[0033]

[0045] As shown in Figure 4, the X-ray beam is an expanding cone extending from the source towards the receiver or image intensifier. The adjusted C-arm assumes a fixed position of the beam cone throughout the surgical procedure. However, movement of the C-arm can introduce errors in the cone beam, causing the beam to shift in the X and Y directions relative to the receiver. Thus, the direction of the cone beam can be posture-dependent. The “posture” of the C-arm is the global position or orientation of the C-arm relative to a globally fixed position, such as the floor of the OR. It can be understood that the posture of the C-arm is determined independently of the patient’s posture or position, whether prone, supine, or lateral. To ensure accurate depiction of the surgical site and the movement of the tracked effector, the influence of the C-arm posture on the cone beam must be demonstrated. Accordingly, the method of this disclosure “characterizes” the C-arm in one or more postures of the C-arm. The "characterization" used here refers to the process of determining the properties or features of the C-arm that affect the X-ray cone beam and, ultimately, the accuracy of the images obtained by the C-arm. Figure 1 shows one orientation of the C-arm 103, where the emitter and detector are aligned essentially directly perpendicular to the patient in order to obtain an AP image. However, during typical surgical procedures, various images of the surgical site, from lateral images to AP images, are required to help the surgeon accurately visualize the surgical site. Thus, the C-arm may be rotated in the direction of arrow 108 relative to the patient, specifically around the global x-axis. It is understood that some C-arms allow rotation in additional degrees of freedom, such as around the global y-axis and z-axis. The global position or orientation of the C-arm can be determined from the position detector mounted on the C-arm by a tracking system that tracks a reference on the C-arm and / or by a gyroscope-type system.

[0034]

[0046] In an ideal state, the physical geometry of the C-arm, and therefore the X-ray cone beam produced and detected by the C-arm, remains unchanged regardless of the C-arm's physical orientation or pose. Naturally, in practice, gravity and the physical properties of the C-arm's structure mean that the C-arm's physical geometry changes based on its orientation and pose. For example, a typical C-arm is known to flex outward (expand the C-shape) when positioned for lateral imaging and to compress (contract the C-shape) when positioned for AP imaging. This flexing and compression of the C-arm results in slight changes in the X-ray beam geometry, causing changes in the positions of the receiver 105 and detector associated with the source 104. Furthermore, the C-arm is sensitive to image distortion (such as pinwheels and pincushions), twisting, detector pixel offset, detector rotation, pixel aspect ratio, source position errors, deformation and flexing over time, and damage. These error sources differ depending on the C-arm. Therefore, it is important to characterize each C-arm to ensure optimal imaging during surgical procedures.

[0035]

[0047] In the example system, each pixel is identified by a coordinate pair (u,v), which is related to physical space by the pixel coordinates (u0,v0) of the physical origin (0,0,0) at the center of the color, the physical increment p between pixels (expressed as pixels / mm), and the aspect ratio r between the vertical and horizontal pixel increments. Furthermore, the C-arm allows the user to rotate the X-ray image by an arbitrary angle a. Moreover, because there may be distortion in the X-ray detector, the pixels do not coincide with a linear grid, and this is due to the angular component a. d and radial component r d These can be modeled as p, r, (u0,v0), a, a d , r dThe values ​​of , the emitter's (X,Y,Z) position, the detector's rotation angle, and image distortion constitute parameters determined in the characterization process. All of these parameters determine where the X-ray cone beam is directed in the reference frame of the adjustment collar or cap (these are fixed to the C-arm). These parameters are used in equations that map the tracked surgical instrument at its global position (x,y,z) to the pixel coordinates (u,v) of several pixels that form an image of the tracked tool. In one system, as disclosed in the '177 patent incorporated by reference, the equations can take the form of equations (1) and (2) below.

[0036]

number

[0037]

[0048]

number

[0038]

[0049] Here,

number

number

[0039]

[0050] Other equations can also be used that incorporate these and other parameters that affect coordinate pairs related to image pixels, such as image distortion and twist. Ideally, the values ​​of these parameters are fixed for all C-arms, and in some cases are null, so the calculated pixel position for any point in the imaged feature does not change. However, in practice, the features of a C-arm can change between C-arms and between C-arm orientations. Among these parameters are (u0,v0), p, r, a, ad and r d Since the error of the estimated value with respect to anything such as etc. from the actual value of these parameters can associate the incorrect pixel specified by the coordinate pair (u, v) with a point in the object to be tracked and imaged, it can be understood that an offset of the image displayed to the surgeon and the radiologic technologist will occur.

[0040]

[0051] According to the present disclosure, the characterization of the C-arm is achieved using a reference or glyph fixed to the emitter and detector of the C-arm, namely, the adjustment color 150 (FIG. 7) and the cap 180 (FIG. 9). In one approach, the C-arm is placed in a baseline position, typically the position shown in FIG. 1, and an image shot is taken. It should be understood that this X-ray image can be obtained independently of any live surgical procedure and before actually using the C-arm in a procedure. Ideally, this C-arm characterization process is initiated when the C-arm is delivered to the medical facility. Next, the resulting characterization information can be used at any time when the C-arm is in use. However, in some cases, it is considered that the characterization radiograph can be an image obtained during a surgical procedure.

[0041]

[0052] When an X-ray image is taken, the reference frame or coordinate system is associated with a fixed position in either the color or the cap, such as the x, y, and z axes and the physical origin (0,0,0) at the center of the detector in Figure 9. The beam source position (Xs,Ys,Zs) and the position of the detector's imaging pixel data are measured in this coordinate system. The pixels are oriented in the image plane, i.e., the xy plane, and optimally aligned on a linear grid. Glyphs 152 and 192 are identified in the X-ray image. Since the physical positions of the glyphs are known, the expected coordinates of the pixels representing those glyphs are also known. These expected coordinate values ​​are used to determine characterization parameters for a particular C-arm in a particular orientation. Specifically, the software of the image processing device is configured to calculate characterization parameters such as those in equations (1) and (2) above. These parameters are associated with a specific C-arm and a specific pose and stored in a database that may be in the image processing device 122, the C-arm control processor itself, or in remote storage such as cloud data storage. Thus, the database includes a unique identifier for a specific C-arm, data on the C-arm's pose, and characterization parameters obtained for that specific pose. The data may be global positioning data generated by a 3D tracking device such as device 130.

[0042]

[0053] As described above, the adjustment collar and cap are components that are attached to the emitter and detector of the C-arm, respectively. Each time these components are attached to the C-arm, they may be attached slightly differently, possibly shifted or rotated from their previous mounting positions. This offset in the attachment of the collar and cap does not change the characterization parameters when they are determined in the characterization process, but this offset shifts the reference frame of the cap or collar relative to the X-ray image produced by the C-arm. Therefore, the characterization parameters may include the offset between the collar and cap from the proper baseline position of the components. This offset can be applied to the formula used to produce the X-ray image, as described above. This offset can be physically measured and entered into imaging software, or it can be obtained through radiographs.

[0043]

[0054] In some cases, the image distortion parameter applied in equation (2), i.e., the angular component a, d and radial component r d This can be obtained using the technique disclosed in the '177 patent, with a BB plate incorporated into or attached to the color 150 or cap 180, or with an adjustment phantom having an embedded BB pattern. In those cases, a second X-ray image can be obtained in a specific orientation to visualize the BB array and determine the image strain parameters. The image strain parameters are stored in a database along with other characterization parameters. Note that not all C-arms exhibit material image strain, in which case strain parameters are not required.

[0044]

[0055] Next, the C-arm can be moved to a different position, such as by rotating from the AP image position to the lateral image position. A new X-ray image of the glyph (and, if necessary, the BB array) is taken, and characterization parameters are derived in the manner described above. Since these X-ray images are obtained independently of the medical procedure, multiple images can be obtained in multiple positions, the purpose of which is to pre-set up the characterization database with sufficient information so that it is possible to extrapolate the characterization parameters to new C-arm positions during the surgical procedure. However, it can be understood that the C-arm can be moved to many positions during the procedure, and most of these will not be the same as any of the positions used to generate the C-arm characterization parameters. In some cases, it may be necessary to interpolate the characterization parameters for the live X-ray position from the stored characterization parameters. Preferably, interpolation is not necessary if the current position of the C-arm is within a predetermined angle from a previous known position, such as within 3 degrees. In one embodiment, the global position of the C-arm pose in a live radiography image can be used to determine two or more previous characterization radiography positions that are globally closest to the live radiography pose. Linear interpolation can be used to estimate characterization parameters from stored characterization parameters.

[0045]

[0056] In some cases, live radiography during a surgical procedure can be used to generate characterization parameters for the new C-arm position during that procedure. The color 150 and cap 180 can be maintained on the C-arm during the procedure, as they are configured to avoid interference with the live radiographic image of the surgical site. During the procedure, the characterization parameters are interpolated for live image generation. During the procedure, glyphs and associated information are stored for each C-arm position as live radiographs are taken. For any given radiograph, characterization parameters can be determined and applied to the above formula while tracking the movement of the surgical effector or instrument. Alternatively, or even further, after the surgical procedure is completed, the accumulated positional data can be processed to determine characterization parameters for each C-arm position. The parameters are stored in a database along with previous characterization parameters for use in improving the current procedure and for use in subsequent live procedures. As time progresses, the database of characterization parameters becomes heavily pre-configured, so at the very least, the interpolation of new characterization parameters for new poses will become more accurate, and at the best, any live C-arm pose will correspond to a stored pose.

[0046]

[0057] It can be understood that the database within an image processing device can contain characterization parameters for multiple C-arms, and each C-arm is assigned a unique identifier, such as a product serial number. Alternatively, the global database can be maintained separately from any image processing device, for example, in cloud storage. The image processing device can be configured to automatically recognize a particular C-arm by reading its unique identifier, and then access the global database to obtain the characterization parameters for that particular C-arm. Even more alternatively, the C-arm itself can maintain a database of unique poses and characterization parameters, and therefore the image processing device can read the characterization parameters when it connects to the C-arm.

[0047]

[0058] Ideally, all C-arms are characterized in the manner described above, and the characterization parameters for all C-arms are updated as new poses and their characterization parameters become available. Each time a C-arm is used in a live procedure, a specific C-arm is identified by a unique identifier, allowing access to the stored characterization parameters for that C-arm. To verify the accuracy of the stored characterization parameters, an X-ray shot can be taken before initiating a live procedure in which the C-arm is in one of the stored poses. If the characterization test is positive, meaning that the characterization parameters of the live shot match the stored characterization parameters, the C-arm is ready for live procedure.

[0048]

[0059] To obtain an X-ray image for characterization testing, the adjustment color 150 is attached to the detector and the cap 180 is attached to the X-ray source, as described above. In some cases, the color and cap may be attached slightly differently between procedures. If the color is offset relative to the cap by a certain amount, such as 2 mm, this offset does not change the stored characterization parameters but shifts the reference frame of the tracking object (color or cap) relative to the X-ray image produced by the C-arm. In this case, the characterization test will be negative, meaning that the characterization parameters will not match. The color-to-cap offset can be measured without X-rays by physically measuring the offset or by comparing tracking data with respect to the color and cap, or it can be measured using an X-ray image in which the offset is determined based on the difference between the characterization parameters. In both cases, the parameters for each adjustment entry can be adjusted to match this offset.

[0049]

[0060] Once the characterization examination is complete, the live procedure continues, and the surgeon obtains X-rays in various poses as needed during the surgical intervention. For each X-ray, the C-arm pose is determined in the manner described above and then compared to the pose value stored in the database. In one configuration, the characterization parameters from the nearest characterized pose are applied to the current pose and used in the image pixel position formula described above. This approach inherently introduces some error unless the poses are identical. However, depending on the proximity of the poses, the resulting error may be negligible. Selecting data for the nearest characterized pose can be limited to maximum offsets, such as the maximum 3D vector offset or the maximum offset in a particular degree of freedom. For example, it has been found that the effect of angular offsets smaller than 3 degrees from the estimated position to the actual position of the cone beam for a conventional C-arm is negligible.

[0050]

[0061] Another approach involves real-time calculations to interpolate the characterization parameters between characterization poses obtained during C-arm characterization. This approach can be used with all new X-ray images and can be limited to new X-ray images where the pose exceeds the maximum proximity offset (i.e., 3 degrees) relative to the stored pose. Any suitable interpolation process can be applied, and various interpolation approaches can be selected based on the characteristics of the pose data. For example, if the only difference between poses is the rotation of the C-arm around the global X-axis, the interpolation can be linear, based on the assumption that the distortion of the C-arm detector and source due to gravity is a linear function of the degree of the C-arm cantilever. If the C-arm takes on a new pose during a live procedure, new data can be generated if adjustment color and source caps are present on the C-arm. The image processor can be configured to distinguish between images of the surgical site and images of the color and cap glyphs. Specifically, since the color and cap glyphs are all located in the outer periphery of the X-ray image, the image processor can easily assign peripheral image pixels to the color and cap. The data from these glyph image pixels can be processed separately from the X-ray image pixels of the surgical site and instruments. Preferably, the color and cap data for the new pose are stored for analysis after the live procedure is completed, at which point the characterization parameters for the C-arm in the new pose are calculated and stored in the database, as described above. It is conceivable that color and cap data for each new pose of the C-arm can be stored during the live procedure, thereby the database of characterization parameters will grow each time the C-arm is used. Eventually, a sufficient number of poses and associated characterization parameters will be available in the database, thereby allowing for the modeling of the C-arm and its deformation over time.If sufficient data is obtained, especially if the C-arm's posture is within the proximity limit as described above, neither procedure will essentially result in a new posture for the C-arm.

[0051]

[0062] After the characterization parameters are updated with respect to the current posture, the characterization parameters are applied to the image pixel formula to produce an accurate image of the surgical site and the surgical effector at that site. The image is then registered in relation to the C-arm collar and cap. Simultaneously or as a secondary step, the image is registered in relation to a fixed reference system, e.g., a stereotactic camera tracking the collar / cap, a reference array attached to the patient, an operating table or other object fixed in relation to the patient's anatomical structure, or any other 3D tracking technology tracking the instrument or the C-arm itself. The information of the tracked tool is then presented to the surgeon in the manner described above.

Claims

1. A method for obtaining X-ray images of anatomical features and surgical effectors in the surgical space of a patient, To detect the position of one or more surgical effectors in the surgical space, and to generate positional data for that purpose. A particular C-arm includes an X-ray emitter and an X-ray detector, the detector including an array of multiple pixels that can be actuated by an X-ray cone beam from the emitter, and detecting a specific orientation of the particular C-arm to obtain a live X-ray image of the surgical space. The process involves determining characterization parameters for a specific C-arm in the aforementioned specific posture, and incorporating these characterization parameters into one or more equations implemented in imaging software stored and implemented by an image processing device, so as to create an image of the anatomical structure in the surgical space detected by the specific C-arm and the surgical effector. The aforementioned image is represented by the pixels of the detector which are activated by the X-ray beam, The position of the pixel is determined by one or more of the above equations as a function of the position data and the characterization parameters of the specific C-arm in the specific orientation, wherein the characterization parameters include a plurality of parameters that are unique to the specific C-arm and depend on the orientation of the C-arm, The above one or more formulas can be used to determine the characteristics of the anatomical structures detected by the X-ray cone beam in the surgical space and the position of the pixels corresponding to the surgical effector. To obtain a live X-ray image of the aforementioned surgical space, The imaging software is operated to produce a live image of the anatomical features and surgical effectors in the surgical space, based on the position of the pixels actuated by the X-ray cone beam, which is determined by one or more of the above equations as a function of the characterization parameters. To display the aforementioned live image and A method that includes this.

2. A method according to claim 1, wherein the step of obtaining characterization parameters comprises identifying the particular C-arm and obtaining only characterization parameters that are unique with respect to the particular C-arm.

3. The method according to claim 1, The characterization parameters include a number of parameters that depend on the orientation of the C-arm, The database includes characterization parameters corresponding to a number of predetermined poses of the C-arm, The step of obtaining characterization parameters includes obtaining from the database a number of predetermined orientations of the C-arm corresponding to a particular orientation of the C-arm, method.

4. The method according to claim 1, The characterization parameters include a number of parameters that depend on the orientation of the C-arm, The database includes characterization parameters corresponding to a number of predetermined poses of the C-arm, The step of obtaining characterization parameters includes obtaining the plurality of parameters from the database that depend on at least two of the plurality of predetermined poses of the C-arm, Prior to the step of incorporating the characterization parameters into one or more equations implemented in imaging software, extrapolate the characterization parameters corresponding to a specific pose from the characterization parameters corresponding to at least two of the numerous predetermined poses of the C-arm. method.

5. A method according to claim 1, wherein the step of obtaining characterization parameters includes obtaining the characterization parameters from a database stored at a location away from the image processing device.

6. A method according to claim 5, wherein the step of obtaining characterization parameters includes obtaining the characterization parameters from a database stored in either the C-arm or the cloud.

7. The method according to claim 3, The process further includes performing a characterization test before detecting a specific pose of a particular C-arm in order to obtain a live X-ray image, wherein the characterization test is The C-arm is positioned in the current position corresponding to the predetermined position, Determining the characterization parameters of the specific C-arm in the current posture, Obtaining the characteristic parameters with respect to the predetermined posture, Comparing the characterization parameters with respect to the current posture with the characterization parameters with respect to the predetermined posture, An error is indicated when the difference between the aforementioned characterization parameters exceeds a threshold. including, method.

8. A method for creating a display of images of internal anatomical structures and radiopaque effectors in a patient within the surgical field during medical procedures, using a C-arm including an X-ray emitter and an X-ray detector, Using the C-arm, a baseline image of the surgical field including the anatomical structure of the patient is obtained. Using the C-arm, an image of the radiopaque effector in the surgical field is obtained independently of the baseline image. Displaying an overlay image that includes the image of the radiopaque effector superimposed on the baseline image of the surgical field, such that the image of the radiopaque effector is positioned relative to the image of the patient's anatomical structure, in the same manner that the actual radiopaque effector is positioned relative to the actual anatomical structure; The tracking system is used to track the position and movement of the radiopaque effector, In the superimposed image, the image of the radiopaque effector is moved according to the tracked motion of the radiopaque effector, Using tracking information from the aforementioned tracking system, the position of the X-ray detector and the actual position of the radiopaque effector relative to the position of the X-ray detector are determined. The method involves displaying a tip mark in the superimposed image, the tip mark corresponding to the actual position of the tip of the radiopaque effector relative to the position of the X-ray detector in the superimposed image, and thereby enabling the detection of an error when the position of the tip mark in the superimposed image is not aligned with the tip of the radiopaque effector image in the superimposed image. A method that includes this.

9. A method according to claim 8, wherein the tip mark is a chevron.

10. The method according to claim 8, Using the tracking information from the tracking system, the direction of the radiopaque effector is determined, The method involves displaying a trajectory marker in the superimposed image, the trajectory marker extending from the tip marker along the direction of the radiopaque effector, and thereby enabling the detection of an error if the direction of the trajectory marker is not aligned with the longitudinal axis of the radiopaque effector in the superimposed image. A method that further includes this.

11. A method for creating a display of images of the internal anatomical structures and radiopaque effectors of a patient in the surgical field during medical procedures, Using a C-arm, an image of the radiopaque effector in the surgical field is obtained, The tracking system is used to track the position and movement of the radiopaque effector, To determine the position of the tip of the radiopaque effector in the image in the surgical field relative to the coordinate system of the C-arm, Using tracking information from the aforementioned tracking system, the position of the tip of the radiopaque effector relative to the coordinate system of the C-arm is determined, Comparing the position of the tip of the radiopaque effector in the image with the position of the tip derived from the tracking information, An error state is determined when the two aforementioned positions differ by more than a predetermined amount. A method that includes this.

12. A method according to claim 11, further comprising displaying a tip marker in the image of the radiopaque effector obtained in the surgical field, the tip marker corresponding to the position of the tip derived from the tracking information, thereby enabling visual determination of an error if the tip marker is not aligned with the tip in the image of the radiopaque effector obtained.

13. A method according to claim 12, wherein the tip mark is a chevron.

14. The method according to claim 12, Using the tracking information from the tracking system, the direction of the radiopaque effector is determined, Displaying trajectory markers in the obtained image of the radiopaque effector, the trajectory markers extending from the tip marker along the tracked direction of the radiopaque effector, and thereby enabling the detection of errors when the direction of the trajectory markers is not aligned with the longitudinal axis of the radiopaque effector in the obtained image. A method that further includes this.

Images