Rotating marker

Abstract

The image-guided surgical marker (40) has: a base (94) with a base shaft that connects to the clamp (42); and an alignment target (44). The alignment target has: a target area (120) having an alignment pattern formed thereon; and a socket (124) connected to the target area and configured to rotatably fit into the base, thereby allowing the alignment target to rotate about the base axis. The alignment target also has an optical indicator (162) in the socket that indicates the angle of orientation of the alignment target about the base axis.

Description

Technical Field

[0001] The present invention generally relates to surgery, and more specifically to surgery performed using augmented reality.

Background Art

[0002] In an augmented reality system used by a surgeon performing surgery, typically, it is necessary to align the patient's reference frame with the reference frame of the augmented reality system used by the surgeon. Alignment methods are known in the art.

[0003] U.S. Patent No. 8,848,977 (Patent Document 1) issued to Bammer et al. describes a method of optical pose detection. An auto-encoding marker is provided in which each feature on the pattern is extended with a two-dimensional barcode.

[0004] U.S. Patent No. 9,220,573 (Patent Document 2) to Kendrick et al. describes a system for tracking a tracking device for use with a surgical navigation system. The system can include at least one tracking device having a plurality of faces, and the faces can be operable to generate signals during operation.

[0005] U.S. Patent No. 9,378,558 (Patent Document 3) to Kajiwara et al. describes that when it is determined that a marker is present within a predetermined region, a self-position / self-orientation calculation unit calculates a self-position and / or self-orientation in a predetermined coordinate system based on the marker in the acquired imaged image data.

[0006] U.S. Patent No. 9,495,585 (Patent Document 4) to Bicer et al. describes a method of finding a one-to-one mapping between a reference marker on a tracked object and a reference marker projection on an image plane captured by a camera in an optical object tracking system.

[0007] U.S. Patent No. 9,943,374 (Patent Document 5) to Merritt et al. describes an image-guided system for tracking surgical instruments during a surgical procedure. The image-guided system includes a plurality of cameras adapted to be disposed outside the surgical area to acquire images of optically visible patterns.

[0008] U.S. Patent No. 10,022,104 (Patent Document 6) to Sell et al. describes a marker including a first marker component having a first hydrogen proton density and a first mass density; and a second marker component having a second hydrogen proton density different from the first hydrogen proton density.

[0009] U.S. Patent No. 10,080,616 (Patent Document 7) to Wilkinson et al. describes a system that generates a three-dimensional representation of bone and reference markers, defines a coordinate system for the three-dimensional representation, and determines the position of the reference markers with respect to the coordinate system.

[0010] U.S. Patent No. 10,108,833 (Patent Document 8) to Hong et al. describes a marker including a pattern formed thereon and an optical system. At least a portion of the pattern that appears specifically by the orientation of viewing the pattern through the optical system from outside the marker is visible from outside the marker.

[0011] U.S. Patent No. 10,251,724 (Patent Document 9) to McLachlin et al. describes a fiducial tile that can be fixed around a part of the spine during a surgical operation and can be tracked by a surgical navigation system.

[0012] U.S. Patent No. 10,296,805 (Patent Document 10) to Yang et al. describes a marker for which at least one of the position and orientation with respect to an acquisition unit is estimated.

[0013] U.S. Patent No. 10,420,626 (Patent Document 11) by Tokuda et al. describes a method for automatic detection and alignment of medical images using reference markers and processing algorithms.

[0014] U.S. Patent No. 10,463,434 (Patent Document 12) granted to Siegler et al. describes a tracking marker support structure including one or more reference markers, and the tracking marker support structure is configured to be removably and securely attached to a skeletal region of a patient.

[0015] U.S. Patent No. 10,504,231 (Patent Document 13) granted to Fiala describes a reference marker that is a printed pattern detected by an algorithm in an image from an image sensor for applications such as automated processes and augmented reality graphics.

[0016] U.S. Patent No. 10,537,395 (Patent Document 14) granted to Perez describes a kinematic connector assembly for kinematically connecting two objects. The kinematic connector assembly includes a receiver that defines a cavity and has a plurality of restraint surfaces accessible within the cavity.

[0017] U.S. Patent Application No. 2003 / 0210812 (Patent Document 15) by Khamene et al. describes an apparatus for pose determination using single camera tracking in a workspace. The apparatus includes a computer programmed to perform pose determination and a tracking camera coupled to the computer to provide a tracking image, and calibration information is stored for the camera.

[0018] U.S. Patent Application 2011 / 0098553 (Patent Document 16) by Robbins et al. describes automatic alignment of magnetic resonance (MR) images executed in an image-guided system by placing an MR-visible marker at a known position relative to a marker visible in a camera tracking system.

[0019] U.S. Patent Application No. 2013 / 0106833 (Patent Document 17) by Fun describes an input device for providing a computer with three-dimensional six-degree-of-freedom data input. The device includes a tracking device having tracking points. One array of the tracking points defines a first axis. Another array defines a second axis or plane orthogonal to the first axis.

[0020] U.S. Patent Application No. 2015 / 0150641 (Patent Document 18) by Daon et al. describes a three-dimensional position and orientation tracking system including one or more pattern tags each including a plurality of reference portions and a tracking device for acquiring image information regarding the pattern tags.

[0021] U.S. Patent Application No. 2016 / 0324583 (Patent Document 19) to Kheradpir et al. describes a patient reference device including a housing having a rear side and a front side, and at least three tracking markers attached to the front side of the housing. The housing extends around the at least three tracking markers and extends beyond a horizontal plane defined by the tops of the at least three tracking markers.

[0022] U.S. Patent Application No. 2017 / 0239015 (Patent Document 20) to Sela et al. describes a device that is at least partially visible by both a three-dimensional (3D) scanner system of a medical navigation system and a tracking system of the medical navigation system.

[0023] Documents incorporated by reference into this patent application are considered an essential part of the application, except when terms are defined in these incorporated documents in a manner inconsistent with the definitions made explicitly or implicitly herein. In case of conflict, only the definitions in this specification should be considered.

Prior Art Documents

Patent Documents

[0024]

Patent Document 1

[0025] One embodiment of the present invention is a marker for image-guided surgery, comprising: a base having a base axis and connected to a tethering device; and an alignment target; the target comprising: a target area having an alignment pattern formed thereon; and a socket connected to the target area and configured to rotatably fit onto the base, such that the alignment target is rotatable about the base axis; and an optical indicator of the socket indicating the orientation angle of the alignment target about the base axis. The marker is characterized by having the above features.

[0026] In one disclosed embodiment, the socket is configured to fit onto the base only in at least two discrete orientations about the base axis. Typically, the configuration of the discrete orientations is symmetrically distributed with respect to the base axis. The discrete orientations have four discrete orientations.

[0027] In a further embodiment, the socket comprises a plurality of openings equal to the plurality of discrete orientations, and the optical indicator is configured to be visible through one of the openings indicating one of the discrete orientations.

[0028] In yet a further disclosed embodiment, the socket includes a plurality of openings equal to the plurality of discrete orientations, and the optical indicator is configured to be visible through an opening selected and arranged to provide a distinct identification of each of the plurality of discrete orientations.

[0029] In an alternative embodiment, the socket is configured to fit onto the base in a plurality of non-discrete orientations about the base axis. The socket includes an opening, the optical indicator coincides with the opening, and a portion of the optical indicator visible through the opening indicates one of the non-discrete orientations. The opening includes a semi-circular arc.

[0030] In a further alternative embodiment, the socket is at a fixed distance from the target area, and the marker further comprises an augmented reality system operating during the patient's surgery and a processor, the processor configured to: track the alignment target during surgery; provide a patient tracking vector in response to tracking of the alignment target; calculate a change in the orientation angle of the alignment target in response to a change in the image of the optical indicator; and add an orientation change vector to the patient tracking vector based only on the fixed distance and the change in the orientation angle to update the patient tracking vector.

[0031] One embodiment of the present invention is a method that enables rotation of a marker during surgery without the need for re-alignment, the method comprising: connecting a base having a base axis to a tethering device; forming an alignment pattern on a target area of an alignment target; connecting a socket to the target area, the socket being at a fixed distance from the target area and configured to be rotatably adapted to the base, whereby the alignment target is rotatable about the base axis; providing an optical indicator for the socket that indicates the orientation angle of the alignment target about the base axis; operating an augmented reality system during the patient's surgery; tracking the alignment target during surgery; providing a patient tracking vector to the augmented reality system in response to tracking of the alignment target; calculating a change in the orientation angle of the alignment target in response to a change in the image of the optical indicator; and adding an orientation change vector to the patient tracking vector based only on the fixed distance and the change in the orientation angle to update the patient tracking vector.

[0032] According to aspects of the present disclosure, a marker for image-guided surgery is disclosed. The marker has a base axis, a base for connecting to a tethering device, and a positioning target. The positioning target has a target area on which a positioning pattern is formed, and a socket connected to the target area and configured to rotatably fit onto the base, whereby the positioning target is rotatable about the base axis, and an optical indicator of the socket that indicates the orientation angle of the alignment target about the base axis.

[0033] In various embodiments of the marker, the socket is configured to fit onto the base only in at least two discrete orientations around the base axis.

[0034] In various embodiments of the marker, the configuration of the plurality of discrete orientations is symmetrically distributed with respect to the base axis.

[0035] In various embodiments of the marker, the plurality of discrete orientations includes four discrete orientations.

[0036] In various embodiments of the marker, the socket comprises a plurality of openings equal to the plurality of discrete orientations, and the optical indicator is configured to be visible through one of the openings indicating one of the discrete orientations.

[0037] In various embodiments of the marker, the socket comprises a plurality of openings equal to the plurality of discrete orientations, and the optical indicator is configured to be visible through the selected and arranged openings so as to provide a distinct identification of each of the discrete orientations.

[0038] In various embodiments of the marker, the socket is configured to fit onto the base in a plurality of non-discrete orientations around the base axis.

[0039] In various embodiments of the marker, the socket includes an opening, the optical indicator coincides with the opening, and a portion of the optical indicator visible through the opening indicates one of the non-discrete orientations.

[0040] In various embodiments of the marker, the opening includes a semi-circular arc.

[0041] According to aspects of the present disclosure, an augmented reality system or a navigation system that operates during a patient's surgery, and / or a tracking system is provided, the system having a marker, the socket being at a certain distance from the target area, and having a storage medium storing machine-executable instructions configured to execute instructions on a processor or a computer system, the processor or the storage medium, when executed: tracking an alignment target during surgery; providing a patient tracking vector in response to tracking of the alignment target; calculating a change in the orientation angle of the alignment target in response to a change in an image of the optical indicator; and adding an orientation change vector to the patient tracking vector based only on a fixed distance and a change in the orientation angle to update the patient tracking vector; and is configured to be.

[0042] In various embodiments of the marker, a mooring device is further provided.

[0043] In various embodiments of the marker, the mooring device is a clamp or a pin.

[0044] According to aspects of the present disclosure, a marker for image-guided surgery is provided. The marker has a base having a base axis; an interface configured to be coupled to a mooring device; and an alignment target; the target having: a target area having an alignment pattern formed thereon; a socket connected to the target area and configured to rotatably fit onto the base, whereby the alignment target is rotatable about the base axis; and an optical indicator of the socket indicating the orientation angle of the alignment target about the base axis.

[0045] In various embodiments of the marker, the base includes an interface.

[0046] In various embodiments of the marker, the interface is coupled to the mooring device to align the base axis of the base with the base axis of the mooring device.

[0047] According to aspects of the present disclosure, a method is provided that enables rotation of a marker during surgery without the need for re-alignment. The method includes connecting a base having a base axis to a tethering device; forming an alignment pattern on a target area of an alignment target; connecting a socket to the target area, the socket being at a fixed distance from the target area and configured to rotatably mate with the base, whereby the alignment target is rotatable about the base axis; providing an optical indicator for the socket that indicates the orientation angle of the alignment target about the base axis; operating an augmented reality system during the patient's surgery; tracking the alignment target during surgery; providing a patient tracking vector to the augmented reality system in response to tracking of the alignment target; calculating a change in the orientation angle of the alignment target in response to a change in the image of the optical indicator; and adding an orientation change vector to the patient tracking vector based only on the change in the fixed distance and the orientation angle to update the patient tracking vector.

[0048] In various embodiments of the method, the socket is configured to mate with the base in only at least two discrete orientations about the base axis.

[0049] In various embodiments of the method, the method further includes a socket, the socket comprising a plurality of apertures equal to the plurality of discrete orientations, and the optical indicator is configured to be visible through one of the apertures that indicates one of the discrete orientations.

[0050] In various embodiments of the method, the socket comprises a plurality of apertures equal to the plurality of discrete orientations, and the optical indicator is configured to be visible through the apertures selected and arranged to provide a distinct identification of each of the discrete orientations.

[0051] In various embodiments of the method, the socket is configured to mate with the base in a plurality of non-discrete orientations about the base axis.

[0052] In various embodiments of the method, the socket includes an opening, the optical indicator coincides with the opening, and a portion of the optical indicator visible through the opening indicates one of the non-discrete orientations.

[0053] According to aspects of the present disclosure, a computer-implemented method for enabling rotation of a marker during surgery without the need for re-alignment, the marker being fixed to a patient and configured to rotatably fit onto a base, and the marker including an alignment pattern and an optical indicator, the optical indicator being configured to indicate the orientation angle of the marker about the base axis of the base, and the optical indicator being at a fixed distance from the alignment pattern, the method comprising: operating a navigation system during a patient's surgery; tracking an alignment target during the surgery; providing a patient tracking vector to the navigation system in response to tracking of the alignment target; calculating a change in the orientation angle of the alignment target in response to a change in an image of the optical indicator; and adding an orientation change vector to the patient tracking vector based only on the fixed distance and the change in the orientation angle to update the patient tracking vector. A method is provided, characterized in that.

Brief Description of the Drawings

[0054] The present invention will be more fully understood from the embodiments with reference to the accompanying drawings:

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B-4C

Figure 4D-4E

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Figure 6A-6B

Figure 6C-6D

Figure 7A-7B

Figure 7C-7E

Figure 8

Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0055] (Overview) In an augmented reality system used during a patient's surgery or medical procedure, it is necessary to track the patient's position or movement (or both). This system typically includes a head - mounted display worn by the medical professional performing the surgery. For example, the tracking performed via a tracking system needs to maintain the alignment between the image of the patient displayed on the display and the image of the patient as seen by the professional.

[0056] To track the position or movement of a patient relative to a display, an alignment target (hereinafter also referred to as a "target") can be fixed to the patient and a processor can be configured to track or determine the relative position of the target (e.g., via a tracking system). In embodiments of the present invention, the target is fixed to the base of a patient tethering device, such as a clamp or pin, that is clamped or inserted into the patient's bone, such that the target functions as a patient marker when attached to the patient tethering device, e.g., the clamp base. According to other embodiments of the present invention, the patient marker includes an alignment target coupled to a patient marker base, and the patient marker can be fixed to the patient via a tethering device, such as a clamp (e.g., the base of the tethering device). When the surgical site is the patient's spine, the bone may include one or more spinous processes of the patient's vertebrae.

[0057] Typically, the position or location of the target of the tracked patient marker is "aligned" to the patient or represents the patient (e.g., used as a reference marker). This "alignment" or representation is used by the processor during surgery. Tracking or determining the target position can maintain alignment between the image of the patient displayed on the display and the patient as seen by the expert, and further, other tracked elements, such as tools used during surgery, can be displayed on the image of the patient. Displaying the tool facilitates navigation of the tool by the expert performing the surgery.

[0058] However, during the procedure, the alignment target may interfere with the ongoing surgery, for example, by obstructing the view of the specialist or restricting the movement of the specialist. In this case, the alignment target may be reoriented or repositioned relative to the fixation device, such as a clamp, and / or the patient, for example, by repositioning the target and / or the clamp to overcome the interference. The reorientation or repositioning can be performed by removing the target from the clamp and then reattaching the target to the clamp, or by repositioning the clamp itself. The above may even require realigning the target with the clamp, repositioning the clamp relative to the bone, and / or performing additional incisions.

[0059] Embodiments of the present invention enable reorientation of the target relative to the patient tethering device without requiring realignment and / or additional manipulation by a specialist. The alignment target includes a target area in which an alignment pattern is formed. The socket included in the alignment target is fixedly connected to the target area at a known distance. The alignment target and / or the fixation device base also includes an optical indicator for the socket indicating the orientation angle of the alignment target about the base axis. According to some aspects, the socket is configured to be rotatably adapted to the base of the tethering device, such as a clamp, so that the alignment target is rotatable about the base axis defined by the base of the clamp. According to some aspects, the patient marker includes an alignment target coupled to the patient marker base. The alignment target includes an optical indicator and is configured to rotate about the axis of the patient marker base.

[0060] During the procedure, the processor operating the augmented reality system can track the alignment targets to provide a patient tracking vector to the system, and the vector maintains the alignment described above. Next, the processor can calculate a change in the orientation angle of the alignment target in response to a change in the image of the optical indicator. Based only on the change in the orientation angle and the known target area - socket distance, the processor can calculate an orientation change vector and add this vector to the patient tracking vector to update the patient tracking vector.

[0061] The updated patient tracking vector functions to automatically update the alignment with the patient's image data of the trajectory of the alignment target, which shows the patient's pose as seen by the expert, and no realignment or additional manipulation is necessary.

[0062] The terms "position" and "location" may be used interchangeably herein. Although the description refers to surgery, the disclosed systems, devices, and methods may be applicable to any suitable medical procedure with the necessary modifications. Although the description refers to spinal surgery or spinal medical procedures, the disclosed systems, devices, and methods may be applicable to medical procedures performed on body structures or parts other than the spine, including hip surgery, hip replacement, or cranial surgery, including joint trauma, with the necessary modifications. Although the description refers to clamps, the disclosed systems, devices, and methods may be applicable to any other patient or bone anchoring device, with the necessary modifications, such as pins inserted into the patient's bone, such as the ilium or cranial tethering frame. Although the description refers to an augmented reality system, the disclosed systems, devices, and methods may be applicable to other navigation and / or tracking and display systems, such as stationary tracking and / or display systems that are not head-mounted, with the necessary modifications.

[0063] (Description of the System) In the following, all references to orientation (e.g., up, down, upward orientation, downward orientation, left, right, top, bottom, above, below, vertical, and horizontal) are used only for identification purposes to assist the reader in understanding the present invention. In particular, they do not create any limitations with respect to the position, orientation, or use of the embodiments of the present invention.

[0064] Referring now to FIG. 1, which is a schematic diagram of a medical procedure according to an embodiment of the present invention. During the procedure performed by the specialist 22, the specialist uses a surgical navigation system 20 that assists the specialist in performing the procedure. The surgical navigation system 20 includes a processor 26 that operates the elements of the system and communicates with an augmented reality assembly 24 worn by the specialist 22 and incorporated into the system. The assembly 24 can be incorporated for attachment to a number of different holding structures of the specialist 22, but in this description, the holding structure is assumed to be similar to glasses. Those skilled in the art of augmented reality will be aware of other possible structures, such as the incorporation of the augmented reality assembly into a head-up display incorporated into a helmet worn by the user of the system 20. All such structures are intended to be included within the scope of the present invention.

[0065] In one embodiment, it is assumed that the processor 26 is incorporated within a stand-alone computer, and the processor typically communicates wirelessly with other elements of the system, including the extended reality assembly 24, as shown in FIG. 1. Optical cables and / or conductive cables may be used for communication. In yet another embodiment, the processor 26 is incorporated within the extended reality assembly 24 or into the mounting portion of the assembly. The processor 26 can typically access the data base 38, which stores images, other visual elements, and any other type of data, including computer code, used by the system 20. Software that enables the processor 26 to operate the system 20 or the assembly 24 (or both) can be downloaded to the processor or the data base 38 in electronic form, for example, via a network. Alternatively or additionally, the software may be provided on a non-transitory tangible medium, such as an optical, magnetic, or electronic storage medium.

[0066] The extended reality assembly 24 includes, among other things, an image acquisition device 72, also referred to herein as a camera 72, having a field of view 74. The camera 72 may be configured to acquire images in the visible spectrum, the non-visible spectrum, or both. The functions of the extended reality assembly 24, the system 20, the processor 26, and the image acquisition device 72 are described below. An assembly similar to the extended reality assembly 24 and its operation are described in U.S. Patent No. 9,928,629 to Benishty et al., the disclosure of which is incorporated herein by reference.

[0067] The medical procedure illustrated herein is performed on a patient 30, and at an initial stage of the procedure, an expert 22 makes an incision 32 in the patient's back. The expert then inserts a spinous process clamp 42 into the incision and positions the opposing jaws of the clamp on either side of the spinous process. The expert adjusts the clamp 42 to grip one or more of the patient's spinous processes selected by the expert.

[0068] The specialist attaches the alignment target 44 to the base 94 of the clamp. Once attached to the base, the alignment target functions as the patient marker 40. Thus, the patient marker 40 includes the alignment target 44 coupled to the base 94. As described below, the patient marker 40 is used by the system 20 to determine the position and orientation of the patient 30 during a medical procedure.

[0069] FIG. 2 is a schematic view showing the assembly 24 according to an embodiment of the present invention. As described above, the augmented reality assembly 24 is configured as, for example, a pair of glasses 50 attached to the frame 54.

[0070] At least one image acquisition device 68 or 72 is attached to the frame 54. Typically, the image acquisition device 68 comprises a camera configured to acquire an image of a scene visible to the specialist's eye, including an image of the marker 40 within the visible spectrum.

[0071] As described above, the augmented reality assembly 24 includes a camera 72 configured to acquire an image of an element of a scene that includes a marker 40 in front of the assembly 24. The image is generated from radiation projected by a projector 73, and the radiation is within a spectrum detected by the camera 72. The projector 73 is disposed proximate to the camera 72 such that retro-reflected radiation from the projector is captured by the camera 72. The camera 72 typically includes a band-pass filter configured to block other radiation, such as radiation projected by surgical lighting. Typically, the camera 72 and the projector 73 operate in a non-visible region of the spectrum, such as the near-infrared spectrum. As described below, typically at least some retro-reflected radiation is received from the patient marker 40, and the processor 26 uses the image of the marker generated by the camera 72 from the received radiation to track the marker and thus the position and orientation of the patient 30. By tracking the position and orientation of the patient 30, the processor can present to the specialist 22 within the augmented reality assembly 24 an image of the patient (e.g., a computed tomography scan) that is correctly aligned with the actual patient as seen by the physician. In some aspects, the camera 72 can be attached to a frame 54 between two lenses of the glasses 50. In some aspects, the projector 73 can include two or more projectors. According to another exemplary embodiment, the augmented reality assembly 24 includes only one acquisition device, such as the camera 72, configured to operate in a non-visible region of the spectrum, such as the near-infrared spectrum. Next, the camera 72 can be configured to acquire an image of the scene as seen by the specialist's eye, including an image of the patient marker 40 in the non-visible spectrum. In some aspects, the camera 72 and the two projectors 73 may be attached to a frame 54 between two lenses of the glasses 50. Each of the projectors 73 may be attached on either side of the camera 72.

[0072] The image acquisition devices 68 and / or 72 and the projector 73 can be attached or arranged at positions other than those illustrated and described with respect to FIGS. 1 and 2 with respect to the frame 54, or can be arranged in other configurations. These are things that can be practiced, implemented, or envisioned by those skilled in the art.

[0073] FIG. 3 schematically shows the situation after the clamp 42 has been inserted into the patient 30 and adjusted according to an embodiment of the present invention. Next, the alignment target 44 is attached to the base 94 of the clamp to form the patient marker 40. The figure shows that the clamp 42 is attached specifically for gripping the bone 21 of the patient 30, specifically for gripping the spinous process 25 of the vertebra of the patient's spine. After attachment, the alignment target 44 is outside the patient's body. As shown in FIG. 3, an exemplary clamp 42 includes teeth protruding inward from the jaws of the clamp, which facilitate the clamp's firm gripping of the spinous process. An exemplary configuration of the patient marker 40 will be described in more detail below with reference to FIGS. 3 and 4A - 4E.

[0074] FIG. 4A is a schematic perspective view of the patient marker 40, and FIGS. 4B - 4E are schematic views of different orientations of the patient marker according to an embodiment of the present invention. As described above, the patient marker 40 is formed by attaching the alignment target 44 to the base 94 of the clamp 42. The clamp will be described later.

[0075] An exemplary clamp 42 includes a pair of jaws 90, 92 at the lower part of the clamp. The jaws are coupled to the clamp base 94 at the upper part of the clamp, and the clamp base includes a jaw adjustment mechanism 96. In the embodiment described herein, the jaw 92 is fixed to the base 94, and the jaw 90 moves relative to the jaw 92. The jaw adjustment mechanism 96 includes an adjustment screw 100, which is coupled to the jaw 90 by a lever 102, and rotation of the screw causes the jaw 90 to approach or retreat from the jaw 92. The hinge pin 98 defines a hinge axis 106 about which the jaw 90 rotates, and each of the jaws 90, 92 is substantially parallel to the hinge axis.

[0076] For the sake of clarity, in the description of this specification, it is assumed that the elements of the marker 40, as an example, refer to a set of xyz orthogonal axes with the center of the hinge pin 98 as the origin. In FIG. 4A, it is assumed that the y-axis corresponds to the hinge axis 106, the x-axis is orthogonal to the plane containing the jaws 90 and 92, and the z-axis is orthogonal to the x-axis and the y-axis.

[0077] The alignment target 44 includes a target area 120 and a socket 124, and the target area and the socket are fixedly connected to each other by a connecting rod 46. Since these are assumed to be in a plane parallel to the x-axis and the y-axis, it is called the xy plane. In an embodiment of the present invention, since the orientation angle of the alignment target 44 with respect to the clamp 42 is measured, a line 126 is constructed from the center 130 of the socket to the center 134 of the target area and extends therefrom, which is assumed to indicate the orientation direction of the alignment target 44 in this specification.

[0078] The target area 120 is, for example, substantially rectangular and includes an optical element 138. The optical element 138 is arranged in a three-dimensional (3D) pattern without a rotational symmetry axis (except for an obvious symmetry axis for 360° rotation). Since there is no symmetric mirror surface, the position and orientation of the target area can be clearly determined from the image of the optical element. The optical element 138 is typically a retroreflector. According to some aspects, the optical element 138 is arranged in a two-dimensional (2D) pattern. Entities having an arrangement of optical elements similar to the arrangement in this specification are described in PCT patent application WO2019 / 211741A1, which is incorporated herein by reference.

[0079] As described above, it is assumed that socket 124 is substantially planar and defines an axis 152 that passes through socket center 130 and is orthogonal to the xy plane. As shown in FIG. 4A, when socket center 130 is on the z axis, axis 152 coincides with the z axis. Socket 124 includes four substantially similar openings 150 that are symmetrically distributed about axis 152. As shown in the callout of FIG. 4C, socket 124 includes a central hole 156, and screw 154 is configured to pass through the hole and connect the socket directly to the upper surface 170 of clamp base 94. When connected, the base axis, including the axis orthogonal to upper surface 170 passing through central hole 156, coincides with axis 152.

[0080] Upper surface 170 is the xy plane and includes four protrusions 174 that are parallel to the xy plane and symmetrically distributed with respect to the z axis. There is an opening 178 in the surface that provides access to adjustment screw 100, and the position of opening 150 is selected such that access to screw 100 is available through one of openings 150 regardless of the orientation of alignment target 44. Also, upper surface 170 has a formed recess 182 that includes an arc 186, and the recess is shaped to receive a colored or retroreflective insert 160.

[0081] As also shown in FIG. 4C, socket 124 includes a flat lower surface 190 in which four depressions 194 are fitted, symmetrically distributed with respect to socket central hole 156 and configured to mate with protrusions 174. A plurality of arcs 198 extend from surface 190, also symmetrically distributed around socket central hole 156 and configured to mate with arc 186 of recess 182.

[0082] Figures 4B - 4E show four different discrete orientations that exemplary alignment target 44 can assume when the target is clamped to the screw 154 such that socket 124 mates with base 94. The clamp corresponds to an orientation of 0°, and these orientations are measured as clockwise rotations about the z - axis from the y - axis. Figures 4B, 4C, 4D, and 4E correspond to alignment targets having individual orientations of 0°, 90°, 180°, and 270° respectively. In each orientation, arc 198 mates with arc 186, protrusion 174 mates with recess 194, wall 196 mates with the outer circular edge of base 94, and the mating ensures that socket 124 is centered with respect to the z - axis.

[0083] As shown in FIGS. 4B - 4E, in each orientation, insert 160 can be seen through one of the openings 150, and the visible insert functions as an optical indicator 162 of the orientation. During operation of system 20, processor 26 calculates the coordinates of the directed line segment between indicator 162 and center 134, and these coordinates function as an orientation measurement reference. Since there is a unique directed line segment, i.e., a unique orientation metric, for each orientation, processor 26 can use the calculated coordinates as an orientation indicator.

[0084] Table I below shows the coordinates of the directed line segment, i.e., the orientation metric, for each of the four exemplary orientations of alignment target 44. The coordinates are calculated assuming that indicator 162 is on the radius r of a circle centered on center 130 of socket 120 and there is a distance D between center 130 and center 134.

Table I

[0085] As described herein, the patient marker 40 is used to track the position of the patient 30, typically the bone of the patient, relative to the assembly 24 by tracking the position of the target region 120. Since the marker is non-flexible, the target region is fixed relative to the bone of the patient to which the patient marker 40 is clamped, and thus tracking of the patient's bone can be achieved by tracking the target region and adding a fixed adjustment vector due to the different physical positions of the target region and the bone.

[0086] Furthermore, since the position of the target region has a one-to-one correlation with the orientation and the positions of different target regions are in known geometric relationships with each other, these geometric relationships can be pre-programmed as changes in orientation and are used to continue tracking the patient when the vector and the orientation of the target region are changed.

[0087] For example, if the target region 120 is at a distance D from the socket 124, the target region is arranged in orientations of 0°, 90°, 180°, and 270° (shown in FIGS. 4B, 4C, 4D, and 4E), and can be represented by two-dimensional ordered pairs (0, D), (D, 0), (0, -D), and (-D, 0), respectively. If the first target region is in the 0° orientation, the geometric relationships for the other three orientations, i.e., the orientation change vectors, are as shown in Table II:

Table II

[0088] It is understood that the three orientation change vectors shown in Table II do not change with the movement of the patient marker 40. These vectors depend only on the initial and final orientations of the target region. Thus, they can be pre-programmed as described above. It will also be understood that the set of three orientation change vectors from other possible initial orientations (90°, 180°, and 270°) can be calculated as in Table II and can be pre-programmed.

[0089] As will be further described below, in embodiments of the present invention, when the orientation of the target site changes, the processor adds an appropriate orientation change vector to the initial tracking vector of the patient marker. This enables continuous tracking of the patient by the marker without re-aligning the marker.

[0090] Figure 5 is a flowchart illustrating the use of markers such as patient marker 40 in the above medical procedure according to an embodiment of the present invention.

[0091] In the first step 200, the specialist 22 attaches a clamp 42 or any other patient tethering device to the bone of the patient 30, which is assumed herein to include the spinous process 25 of the patient, by rotating the screw 100.

[0092] In the target attachment step 204, the specialist attaches the alignment target to the patient tethering device in a specific orientation. The alignment target includes an optical indicator that indicates the current orientation of the marker. For example, the alignment target 44 can be attached to the clamp by aligning the socket 124 with the upper surface 170 of the clamp base 94 and screwing in the screw 154. Thus, after attachment, the insert 160 can be seen through one of the openings 150 and functions as the optical indicator 162.

[0093] The set of orientation metrics for the values of r and D, and the orientation of the alignment target, described above with reference to Table I, can be input to the processor 26 or accessed by the processor 26. The vector coordinates described above with reference to Table II can also be input to or accessed by the processor.

[0094] In the image acquisition step 208, images of the alignment marker's optical element and the optical indicator are acquired via the head-mounted assembly. Referring to FIGS. 1 and 2, for example, using camera 72 and / or one or more image acquisition devices 68, images of the optical elements 138 of the target region 120 and the optical indicator 162 are captured. As an option, the image can include regions close to the patient's bone, such as a tool navigated in a region close to the patient's bone 30 or incision 32 and / or bone or alignment target 44. Then, the tool position can be identified relative to the patient via the tool marker and the alignment target (patient marker).

[0095] In the analysis step 212, the processor analyzes the acquired image to identify the alignment target and / or find a location including the orientation and position of the alignment target.

[0096] For example, the processor analyzes the acquired image to identify and / or find a location including the orientation and position of the target region 120. The position of the target region is assumed to coincide with the center 134 herein as an example. Once the position of the target site is found, the processor can start tracking the target site, for example, by capturing an image of the target site once at a predetermined time interval.

[0097] The processor also identifies the optical indicator of the alignment target in the acquired image. For example, the processor 26 can find the position of the optical indicator 162 in the image. From the coordinates of the two positions, the processor calculates the coordinates of the orientation metric (such as in Table I) that combines the positions and identifies the orientation of step 204 from the metric stored in step 204.

[0098] In adjustment step 216, the processor utilizes the images obtained in step 208, such as of bone, regions close to bone, and / or tools navigated in regions close to bone, to generate an augmented reality display to the expert within the augmented reality assembly 24. The expert adjusts the coordinates of the presented image to match the actual image visible to the expert through the assembly, and the processor stores the adjusted coordinates. The processor then applies the stored adjusted coordinates as an adjustment vector to the presented image along with the tracking of the tracking region (initiated in step 212), continuously aligning the presented image to patient 30.

[0099] The processor continues to apply the stored adjustment vector that functions as a patient tracking vector as long as the orientation in step 204 does not change. It will be understood that alignment using the stored adjustment vector cancels out the relative movement between the patient and the augmented reality assembly 24.

[0100] Steps 200 - 216 correspond to the initial setup of the navigation system 20. Steps 220 - 232, described below, correspond to the steps of a flowchart that can be implemented during a medical procedure in which the system 20 is used.

[0101] In subsequent imaging step 220, images of the alignment target and, optionally, additional elements of interest (e.g., tools used during the procedure or regions of interest of the patient's body) are continuously acquired (e.g., once within a predetermined time interval). For example, images of the alignment target 44 including the target region 120 and the optical indicator 162 are continuously acquired via the augmented reality assembly 24 (optionally, but not necessarily, controlled arbitrarily by the processor 26). From the images of the target region 120 and the indicator 162, the processor calculates an orientation metric.

[0102] In decision step 224, the processor checks whether the orientation metric calculated in step 220 is different from that calculated in step 212 to check whether the target area has changed its orientation. If the decision returns a negative, i.e., there is no change in orientation, in continuation step 228, the processor continues to use the existing adjustment coordinates, i.e., those of step 216.

[0103] If the decision returns an affirmative, i.e., there is a change in orientation, in update step 232, the processor calculates the updated adjustment coordinates by adding the appropriate orientation change vector from step 204 to the existing adjustment coordinates. The processor applies the updated coordinates when presenting the patient's image, e.g., an image of an area close to the bone, to the expert 22 within the augmented reality assembly 24.

[0104] It will be appreciated that an affirmative response in decision 224 is typically caused by the expert 22 changing the orientation of the alignment target. The expert can change the orientation, for example, by loosening the screw 154, readjusting the socket 124 on the upper surface 170 so that the alignment target 44 is in the new orientation, and then screwing in the screw 154 to fix the alignment target in its new orientation. In some embodiments, the expert can temporarily stop tracking the alignment target 44 while positioning the alignment target 44 in its new orientation.

[0105] The expert typically relocates the alignment target 44 to improve access to and / or visibility of a part of the patient. It will be appreciated that it is not necessary to repeat steps 200 - 216 after relocation since the new adjustment coordinates can be calculated from the known geometric relationship between the two orientations of the alignment target 44. (Since the screw is aligned with the opening, the adjustment screw 100 can always be accessed through one of the openings 150 regardless of the change in position.)

[0106] From steps 228 and 232, control returns to decision step 220, so during the procedure, the processor repeatedly applies steps 220 - 232.

[0107] Figures 6A - 6D are schematic views of different orientations of patient marker 240 according to an embodiment of the present invention. Patient marker 240 includes a clamp base 294 coupled to alignment target 244. Clamp base 294 is the base of clamp 242. Except for the differences described below, the operation of patient marker 240, clamp 242, clamp base 294, and alignment target 244 is substantially the same as that of patient marker 40, clamp 42, clamp base 94, and alignment target 44, and elements denoted by the same reference numerals in both patient markers have substantially the same structure and operation. With respect to patient marker 40, alignment target 244 has four different discrete orientations with respect to clamp 242. The axis of patient marker 240 is the same as that of patient marker 40.

[0108] In contrast to the upper surface 170 of clamp base 94 of clamp 42, a circular turret 300 rides on the upper xy - plane 270 of clamp base 294 of clamp 242. Turret 300 includes a recess 308 configured to receive an insert 260 that is typically colored or retro - reflective.

[0109] With respect to socket 124, socket 224 of alignment target 244 includes four openings 250 symmetrically distributed about the center of the socket. However, socket 224 is smaller than socket 124, and openings 250 are not aligned with screw 100 regardless of the orientation of the alignment target. In those of FIGS. 6A, 6C, and 6D, screw 100 is accessible from the outside of the socket.

[0110] Connecting rod 246 connects alignment target 120 to socket 224 but is typically narrower than connecting rod 46.

[0111] Socket 224 has a lower circular wall 316 with an inner surface configured to mate with turret 300. Four mating clips 312 are set within the wall, symmetrically distributed with respect to the center of the socket and arranged to mate with protrusions. When clip 312 mates with raised portion 304, wall 316 holds socket 224 so as to surround and contact the outer surface of turret 300, and the socket is fixed to the turret.

[0112] Since raised portion 304 and mating clips 312 are symmetrically distributed, it is understood that alignment target 244 can mate with clamp 242 in one of the four orientations shown in FIGS. 2 and 3, and that in each orientation, the center of socket 224 is aligned with the center of turret 300.

[0113] Unlike patient marker 40 in which optical indicator 162 is formed from insert 160 being visible through one of openings 150, in patient marker 240, optical indicator 262 includes insert 260 such that it is viewable through three openings 250 as shown in FIGS. 6A - 6D.

[0114] The description of the flowchart of FIG. 5 applies to patient marker 240 with necessary modifications. For example, the position of indicator 262 can be assumed to be the position of the central opening among the three openings 260.

[0115] Patient markers 40 and 240 each have four individually symmetrically distributed orientations. However, embodiments of the present invention can have other numbers of symmetrically distributed orientations, which can be as few as two.

[0116] The number of openings 150 corresponds to the number of individual orientations. As illustrated by indicator 162, the number of openings used to generate an optical indicator may be a single opening. Alternatively, as illustrated by indicator 262, the number of openings used to generate an optical indicator can include any fixed number of openings that is at least one less than the total number of openings. In this case, the openings are selected and arranged to provide a distinct identification of each of the discrete orientations when rotated.

[0117] Accordingly, in the case of four openings corresponding to four discrete orientations, the indicator can be two adjacent openings, but cannot be two openings facing each other, because each of the two opposing openings does not provide a distinct identification of each orientation.

[0118] Figures 7A - 7E are schematic views of different orientations of patient marker 440 according to an embodiment of the present invention. Patient marker 440 includes a clamp base 494 coupled to alignment target 444. Clamp base 494 is the base of clamp 242. Aside from the differences described below, the operation of patient marker 440, clamp 442, clamp base 494, and alignment target 444 is substantially the same as that of patient marker 40, clamp 42, base 94, and alignment target 44, and elements denoted by the same reference numeral in both patient markers have substantially the same structure and operation. Different from patient marker 40 where alignment target 44 can only perform discrete orientations with respect to clamp 42, alignment target 444 within patient marker 440 can perform a plurality of non - discrete and substantially continuous orientations that vary from 0° to 360° with respect to clamp 442.

[0119] Figures 7A - 7E are drawn on the xyz - axis of the same set as the patient marker 40 (however, the axes are rotated 180° compared to those in Figures 4B - 4E), and the orientation is measured as a clockwise rotation from the y - axis centered on the z - axis from the patient marker 40. Figures 7A, 7B, 7C, and 7D respectively correspond to alignment targets having orientations of 0°, 90°, 180°, and 270° with respect to the clamp.

[0120] Figure 7E shows an alignment target having an orientation of θ with respect to the clamp, where 0° ≤ θ < 360°, and the coordinates of the center point of the target area are marked as (Dsinθ, Dcosθ). Here, D is the distance from the z - axis to the center point of the target area.

[0121] In contrast to the upper surface 170 of the clamp base 94 of the clamp 42, the upper xy - plane 470 of the upper plate 476 of the clamp base 494 is circular. The surface 470 has a central circular depression 454 symmetrically arranged on the surface, and the depression ends with an internal thread at its lower end. The surface 470 also has a depression 464 in the form of a semi - circular arc centered on the center of the circular surface 470. An insert 460, which is semi - circular and typically colored or retro - reflective, is inserted into the depression 464, and the insert is sized such that its upper surface is at the same height as the surface 470.

[0122] The socket 424 of the alignment target 444 has a flat lower surface 490 surrounded by a circular wall 496 configured to fit with the outer cylindrical surface 474 of the upper plate 476. A plurality of arcs 498 extend from the lower surface 490, and they are distributed symmetrically around the socket central hole 456 and are configured to fit with the circular depression 454. The socket 424 also has a semi - circular opening 468 that coincides with the insert 460.

[0123] The alignment target 444 is coupled to the clamp 442 by attaching the socket 424 to the upper plate 476 such that the circular wall 496 mates with the outer cylindrical surface 474 and the arc 498 mates with the circular recess 454. Once coupled in this manner, the alignment target 444 can be fixedly held in place in any selected orientation by an expert 22 by screwing the screw 472 into the circular recess 454 at the end of the screw.

[0124] During the procedure, the processor 26 can determine the orientation of the alignment target as a value between 0° and 360° by imaging the insert 460 and using the imaged insert as an optical indicator 462 of orientation. In one embodiment, the processor 26 determines the orientation by finding the portion of the insert visible through the opening 468 and the visible position of the insert.

[0125] In embodiments of the present invention, the fraction may include a fractional region of the insert or, alternatively or additionally, a fractional length dimension such as the arc length of the insert. In some embodiments, a Vernier scale can be used to measure the fractional length dimension.

[0126] Accordingly, FIG. 7A shows the maximum of the insert visible through the opening corresponding to an orientation of 0°, and FIG. 7C shows the minimum of the insert visible through the opening corresponding to an orientation of 180°. FIG. 7B corresponding to an orientation of 90° shows that half of the insert is visible, and the visible half is located below the x-axis, and FIG. 7D corresponds to an orientation of 270° and shows that half of the insert is visible and the visible half is above the x-axis.

[0127] Other methods for determining the orientation of the alignment target from the imaged insert, such as finding the coordinates of the endpoints of the imaged insert or the coordinates of the midpoint on the image, will be apparent, and all such methods are included within the scope of the present invention.

[0128] During the procedure, as described above, the processor 26 determines the orientation of the alignment target 444 from the imaged optical indicator 462. The flowchart of FIG. 8 below illustrates how the processor uses the orientation values during the procedure.

[0129] FIG. 8 is a flowchart illustrating the use of patient markers such as patient marker 440 in the medical procedure described above, and FIG. 9 is a diagram illustrating some steps of the flowchart according to an embodiment of the present invention.

[0130] The first step 600 in which the clamp 442 is attached to the patient's bone is substantially the same as the first step 200 described above.

[0131] In the attachment step 604, the specialist 22 attaches the socket 424 to the socket base 494 and the alignment target 444 to the clamp 442 in a convenient orientation. The specialist uses the screw 472 to fix the alignment target to the clamp base.

[0132] The imaging step 608 is substantially the same as the step 208 described above.

[0133] In the analysis step 612, the processor analyzes the image of the indicator 462 to determine the orientation angle θ of the alignment target having the clamp 42, as described above with reference to FIG. 7E. Further, the processor calculates the position coordinates of the target region 120 from the image of the region acquired in step 608.

[0134] The adjustment or alignment step 616 is substantially the same as that described above for step 216. Thus, in step 616, the coordinates of the presented image are adjusted or aligned so as to match the actual image visible to the specialist through the augmented reality assembly 24. The processor 26 stores the adjustment coordinates and applies the stored coordinates as an adjustment vector to align and track the presented image with respect to the patient 30.

[0135] Steps 600 - 616 correspond to the initial setup of the navigation system 20 for the patient marker 440. The steps 620 - 632 described below correspond to the steps of a flowchart that can be implemented during a medical procedure in which the system 20 is used.

[0136] In the next imaging step 620, an image of the alignment target 444 including the target region 120 and the optical indicator 462 is acquired once, for example, at a predetermined time interval. As an option, an image of the patient 30 can also be acquired. From the image of the optical indicator 462, the processor calculates the orientation angle α of the target region 120 with respect to the clamp.

[0137] In the decision step 624, the processor checks whether the angle calculated in step 620 is different from the angle calculated in step 612 to check whether the target region has changed its orientation. If the decision returns a negative, that is, if there is no change in orientation, in the continuation step 628, the processor continues to use the existing adjustment coordinates, that is, those of step 616, as the adjustment vector.

[0138] If the decision 624 returns an affirmative, that is, if there is an orientation change, in the update step 632, the processor calculates the orientation change vector and adds it to the existing adjustment vector so that the processor can maintain the alignment of the patient 30's image with the patient.

[0139] FIG. 9 is a schematic diagram showing how the processor calculates the orientation change vector according to an embodiment of the present invention. The line segment PA having a length D represents the initial orientation of the adjustment target 444, A is the center of the region 120, θ1 is the orientation of the center, and both values are measured in step 612. A has the coordinates (Dsinθ1, Dcosθ1).

[0140] The line segment PB with length D represents the subsequent orientation of the alignment target 444, where B is the center of region 120 and θ2 is the central orientation, and both values are measured in step 620. B has coordinates (Dsinθ2, Dcosθ2).

[0141] As shown in equation (1), the processor 26 calculates the orientation change vector [AB] as the difference between the coordinates of B and the coordinates of A. [AB]=(D(sinθ2 - sinθ1), D(cosθ2 - cosθ1)) (1)

[0142] Returning to the flowchart of FIG. 8, at step 632, the processor adds the orientation change vector calculated as described in equation (1) to the existing adjustment vector.

[0143] From steps 628 and 632, control returns to the imaging step 620, and following its decision step 624, the processor repeatedly applies steps 620 - 632 during the procedure.

[0144] A positive return from decision step 624 is typically caused by the expert 22 changing the orientation of the alignment target 444 by loosening and then tightening the screw 472. In some embodiments, the expert can temporarily stop tracking the alignment target 444 while placing the alignment target in a new orientation. By repeating steps 620 - 632, the processor continues to accurately align the acquired images of the patient 30 with the patient, so it should be understood that there is no need to repeat steps 600 - 616 after changing the orientation.

[0145] According to some aspects, a patient marker is disclosed herein that includes an alignment target and a patient marker base that can be fixed to a patient via a mooring device. The alignment target is coupled to the base because the screw is aligned with the opening. The alignment target is configured to rotate about the axis of the patient marker base. The alignment target includes an optical indicator. The optical indicator indicates the orientation angle of the alignment target about the axis of the patient marker base. The patient marker further includes a mooring interface. The mooring interface is coupled to the patient marker base. According to some aspects, the patient marker base includes the mooring interface. The alignment target can include a socket configured to rotatably mate with a target base. The patient marker is mounted in a fixed manner via the mooring interface to a patient mooring device, such as the base of the mooring device, and the axis of the patient marker base is aligned with the axis of the mooring device base (e.g., the axis of the clamp base). The optical indicator can be configured to operate according to, for example, optical indicators 162, 262, or 462 as described with respect to FIGS. 4A-4E, 6A-6D, and 7A-7E. The alignment target can be configured to rotate about the axis of the patient marker base according to, for example, the rotation mechanism described in FIGS. 4A-4E, 6A-6D, and 7A-7E. One of ordinary skill in the art will understand how to implement different mechanisms for optical indicators and different rotation mechanisms for alignment targets, including those disclosed herein, in a patient marker that includes a rotatable alignment target coupled to the base of the marker. The above description explains, for example, how an optical indicator, such as indicator 162, can be used with the optical element 138 of the alignment target 44 to find the orientation angle of the alignment target about the axis of the base to which the alignment target is connected. The base can be the base of a mooring device, such as a marker base or a clamp base. It will be understood that the optical element 138 identifies the alignment target.

[0146] In some embodiments of the present invention, the expert 22 uses a surgical tool in the medical procedure mentioned above (Figure 1). The tool has a tool marker connected to the tool or integrated into the tool at a predefined position, and the augmented reality assembly (e.g., augmented reality assembly 24) is configured to enable tracking of the position of the tool tip (e.g., by the processor 26). In these embodiments, instead of using an optical indicator such as the optical indicator 162 to identify the alignment angle of the alignment target, the expert 22 can use the tool to find the angle as described below.

[0147] The patient tethering device or patient marker base can comprise a fixed tool point (hereinafter also referred to as the "tool point"). The tool point position is configured to be fixed relative to the tethering device and thus relative to the patient. For example, the fixed tool point can be connected to the base of the tethering device. Generally, a tool to which a tool marker is attached is calibrated before being used in a medical procedure via an augmented reality assembly. In the calibration process, a spatial ratio between the tool marker and the tool tip, such as a vector between the tool marker (e.g., a pre-set point of retroreflection on the tool marker) and the tool tip, is determined. An expert can touch the fixed tool point at the tip of the calibrated tool while the alignment target of the patient marker is oriented in a specific orientation relative to the tethering device. An image of the tool marker and the oriented patient marker is acquired by an acquisition device of the augmented reality assembly. The position of the fixed tool point relative to the alignment target is determined based on the image by a processor such as processor 26. Subsequently, the orientation of the alignment target relative to the tethering device and thus to the patient can be determined. According to some aspects, an expert can be instructed by the augmented reality assembly (e.g., by software executed by processor 26) to touch the fixed tool point at the tool tip. According to some aspects, the alignment target has a plurality of predetermined orientations, and vectors between the alignment target and the fixed tool point in each orientation are calculated in advance. In such a case, for example, instead of an exact calculation of the position of the alignment target, a spatial region corresponding to each pre-set orientation of the alignment target can be determined and used when determining the orientation of the alignment target. As described above, the acquisition device continuously acquires images of the region of interest including the patient marker and the tool marker. For each image acquired via the acquisition device, the processor can check whether the tool tip is substantially positioned at a possible tool point position corresponding to a possible orientation of the alignment target to identify contact of the tool point by the tool tip. Identification of a specific such position in one or more subsequent images can determine the orientation of the alignment marker.

[0148] One of ordinary skill in the art will be able to make the necessary changes to adapt the description to various configurations of alignment targets, including target 44, 244, and 444.

[0149] It will also be understood that embodiments of the present invention can measure discrete orientation changes, for example, of 0°, 90°, 180°, or 270°, or continuous changes in orientation over substantially any angle between 0° and 360°.

[0150] It will be understood that the above-described embodiments are given by way of example, and that the present invention is not limited to those specifically shown and described above. Rather, the scope of the present invention includes both the various combinations and sub-combinations of the above-described features, as well as those variations and modifications thereof that are not disclosed in the prior art and that will occur to one of ordinary skill in the art upon reading the above description.

Claims

**Claim 1** A marker for image-guided surgery, comprising: a base having a base axis and connected to an anchoring device; and an alignment target; having wherein the target comprises: a target area having an alignment pattern formed thereon; and a socket connected to the target area and configured to rotatably fit to the base such that the alignment target is rotatable about the base axis; and an optical indicator configured to be visible through at least one opening of the socket and indicating the orientation angle of the alignment target around the base axis; having A marker characterized by the above. **Claim 2** The marker according to claim 1, wherein the socket is configured to fit to the base only in a plurality of discrete orientations around the base axis. **Claim 3** The marker according to claim 2, wherein the plurality of discrete orientations are symmetrically distributed with respect to the base axis. **Claim 4** The marker according to claim 2 or 3, wherein the plurality of discrete orientations have four discrete orientations. **Claim 5** The marker according to any one of claims 2 to 4, wherein the socket comprises a plurality of openings equal to the plurality of discrete orientations, and the optical indicator is configured to be visible through one of the plurality of openings indicating one of the plurality of discrete orientations. **Claim 6** The marker according to any one of claims 2 to 4, wherein the socket includes a plurality of openings equal to the plurality of discrete orientations, and the optical indicator is configured to be visible through an opening selected and arranged to provide a distinct identification of each of the plurality of discrete orientations. **Claim 7** The marker according to claim 1, wherein the socket is configured to fit to the base in a plurality of non-discrete orientations around the base axis. **Claim 8** The marker according to claim 7, wherein the optical indicator coincides with the at least one opening, and a portion of the optical indicator visible through the at least one opening indicates one of the plurality of non-discrete orientations. **Claim 9** The marker according to claim 8, wherein the at least one opening includes a semi-circular arc. **Claim 10** The marker according to any one of claims 1 to 6, further comprising the anchoring device.

11. The marker according to any one of claims 1 to 9, wherein the mooring device is a clamp or a pin.

12. An augmented reality system, a marker according to any one of claims 1 to 11, wherein the socket is at a certain distance from the target area, the marker; a processor; having, the processor: tracking an alignment target; providing a patient tracking vector in response to tracking of the alignment target; calculating a change in the orientation angle of the alignment target in response to a change in an image of the optical indicator; and adding an orientation change vector to the patient tracking vector based on a fixed distance and a change in the orientation angle to update the patient tracking vector; configured to An augmented reality system characterized by this.

13. A marker for image-guided surgery, a base having a base axis; an interface configured to be coupled to a mooring device; and an alignment target; having, the target: a target area having an alignment pattern formed thereon; a socket connected to the target area and configured to rotatably fit to the base such that the alignment target is rotatable about the base axis; and an optical indicator configured to be visible through at least one opening of the socket and indicating the orientation angle of the alignment target about the base axis; having, A marker characterized by this.

14. The marker according to claim 13, wherein the base includes the interface.

15. The marker according to claim 13 or 14, wherein the interface is connected to the mooring device so as to align the base axis of the base with the base axis of the mooring device.

Images