Fiducial markers

Abstract

A medical marking device includes a radiolucent plate having a first plurality of radiopaque elements embedded in the plate in a first predetermined pattern and a second plurality of optical reflectors positioned on a surface adjacent the plate in a second predetermined pattern. The device also includes an S-shaped mounting arm having a first end connected to the radiolucent plate and a second end containing one or more fastening receptacles.

Description

Field of the Invention

[0001] The present invention relates generally to fiducial markers, and more particularly to markers that can be used for registration of multiple reference frames present in image-guided surgery. Background of the Invention

[0003] In augmented reality systems used for image-guided surgery, the system must track objects used in the procedure and / or elements of the patient undergoing surgery. This tracking requires registration of the various reference frames used during surgery, including the patient's frame of reference and the frame of reference of the fluoroscopic device used to image the patient. Registration typically requires fiducial markers, and many such markers are known. References describing examples of these markers are provided below.

[0004] US Patent 6,314,310 to Ben-Haim et al. describes an apparatus for x-ray guided surgery. The apparatus includes a reference element placed in contact with a subject's body, and the element includes a plurality of fiducial markers.

[0005] US Patent No. 7,107,091 to Jutras et al. describes a surgical device adapted for use with an image-guided surgical system. The device facilitates monitoring of interdependent movable bone elements.

[0006] US Patent No. 9,179,984 to Teichman et al. describes a navigation system including a multi-configuration tracking array. Multiple tracking devices may be located on the multi-configuration tracking array.

[0007] US Patent 9,498,231 to Haider et al. describes computer-assisted surgery using a tool tracking system.

[0008] Doan et al., US Patent No. 9,844,413, describes a monitoring system for tracking invisible structures of the body in three dimensions. A tracker obtains image information of the object and nearby instruments, all of which are marked with 3D tracking markers of at least one pattern segment.

[0009] US Patent No. 9,872,733 to Shoham et al. describes a system that provides mechanical guidance for distal screw drilling during intramedullary nailing procedures. The drill guide is automatically positioned relative to the distal locking nail hole by a robot using data obtained from x-ray fluoroscopy images.

[0010] Yang et al., U.S. Patent No. 10,034,713 and U.S. Patent Application No. 2017 / 0252109, describe a system for tracking the position and orientation of a handheld tool. A support member secures one or more markers relative to a longitudinal portion of the handheld tool, and a marker plane containing the markers is oriented at an angle relative to the longitudinal axis of the longitudinal portion.

[0011] Wilkinson et al., US Patent 10,080,616, describes a system for accessing image data of a bone to which an array of reference markers is affixed.

[0012] Lavallee et al., U.S. Patent No. 10,085,709 and U.S. Patent Application 2017 / 0164919 describe projecting a 3D image onto at least a portion of a 2D X-ray image and adjusting the projection geometry of the image, the adjustment including registering the image with a projection of an initial 3D image using image-to-image registration techniques.

[0013] McLachlin et al., U.S. Patent No. 10,166,079, describes performing intraoperative image registration in a medical procedure. A depth-encoded marker is provided to an object of interest. The marker is imageable by at least two imaging systems and has asymmetry in at least the depth dimension.

[0014] U.S. Patent No. 10,194,993 to Roger et al. describes a system for assisting in performing surgery on a patient. The system includes a display device and a storage device storing an image of at least a portion of the patient's anatomy, including one or more surgical navigation markers positioned on the patient, for display on the display device.

[0015] US Patent Application 2011 / 0004259 to Stallings et al. describes an apparatus for locating a fiducial marker on an anatomical structure. The apparatus includes a fiducial base and a fixing member. The fiducial base includes a turn and an extension configured to position the fiducial marker within the field of view of a tracking sensor.

[0016] US Patent Application 2011 / 0098553 to Robbins et al. describes performing automatic registration of magnetic resonance images in an image-guided system by placing magnetic resonance (MR) visible markers at known positions relative to markers visible in a camera tracking system.

[0017] Doan et al., U.S. Patent Application 2015 / 0150641, describes a position and orientation tracking system having one or more pattern tags, each tag including a plurality of contrasting portions. The system includes a tracker for obtaining image information about the pattern tags and a database containing geometric information describing a pattern on the pattern tags.

[0018] Cameron et al., US Patent Application 2015 / 0366620, describes a guide for use with an access port for port-based surgery. The guide includes a body positionable over a surgical opening and a handle coupled to the body for removably receiving the access port into the surgical opening.

[0019] U.S. patent application 2017 / 0281283 to Siegler et al. describes a tracking marker support structure comprising one or more fiducial reference markers, wherein the tracking marker support structure is configured to be removably and securely attached to a bone region of a patient.

[0020] Kostrzewski's U.S. patent application 2018 / 0200002 describes a robotic surgical system with built-in navigation capabilities for patient position tracking and surgical instrument guidance during surgery without the need for a separate navigation system.

[0021] U.S. patent application 2018 / 0318035 by McLachlin et al. describes a reference knot that is fixed around a portion of the spine during surgery and tracked by a surgical navigation system.

[0022] Abhari et al., U.S. Patent Application 2019 / 0015163, describes how to determine navigation information related to a site of a medical procedure. The navigation information is then mapped to a common coordinate space to determine the navigation information relative to a field of view of a stored and real-time optical image of the surgical site.

[0023] Documents incorporated by reference into this patent application are considered an integral part of this application, to the extent that, except where any term is defined in these incorporated documents in a manner that conflicts with a definition explicitly or implicitly made in this specification, only the definitions in this specification shall prevail. SUMMARY OF THE INVENTION

[0025] An embodiment of the present invention provides a medical marking device, the medical marking device comprising:

[0026] a radiolucent plate having a first plurality of radiopaque elements embedded in the radiolucent plate in a first predetermined pattern and a second plurality of optical reflectors positioned on a surface proximate the plate in a second predetermined pattern; and

[0027] An S-shaped mounting arm has a first end connected to the radiolucent plate and a second end containing one or more fastening receptacles.

[0028] Typically, the S-shaped mounting arm is radiolucent.

[0029] In a disclosed embodiment, the S-shaped mounting arm includes a first curved section connected to a second curved section by a straight section.

[0030] In further disclosed embodiments, the S-shaped mounting arm includes a first curved section directly connected to a second curved section.

[0031] In yet another disclosed embodiment, the first predetermined pattern and the second predetermined pattern have no axis of symmetry and no plane of symmetry.

[0032] According to an embodiment of the present invention, there is further provided a device, comprising:

[0033] a surgical clamp for attachment to a patient's bone;

[0034] a spacer having a first surface and a second surface, the spacer being configured to be fixedly coupled to the surgical clamp; and

[0035] A marking device, comprising:

[0036] a radiolucent plate having a plurality of radiopaque elements embedded in the radiolucent plate in a predetermined pattern; and

[0037] An S-shaped mounting arm has a first end fixedly connected to the radiolucent plate and a second end configured to mate with a first surface of the spacer and including one or more fastening sockets configured for removable connection of the arm to the spacer.

[0038] In an alternative embodiment, there is a fixed distance between the first surface and the spacer surface.

[0039] In another alternative embodiment, the first surface includes a first plate and the second surface includes a second plate, the device further having an adjustable mechanism connecting the first plate and the second plate, the adjustable mechanism being configured to adjust the spacing between the plates.

[0040] According to an embodiment of the present invention, there is further provided a device, comprising:

[0041] a surgical clamp for attachment to a patient's bone;

[0042] a clamp adjustment element configured to effectuate said attachment;

[0043] a support structure surrounding the clamp adjustment element; and

[0044] A marking device, comprising:

[0045] a radiolucent plate having a plurality of radiopaque elements embedded in the radiolucent plate in a predetermined pattern; and

[0046] An S-shaped mounting arm has a first end fixedly connected to the radiolucent plate and a second end containing one or more fastening sockets configured for removable connection of the arm to the support structure.

[0047] According to an embodiment of the present invention, a method is further provided, comprising:

[0048] embedding a first plurality of radiopaque elements arranged in a first predetermined pattern in the radiolucent plate;

[0049] positioning a second plurality of optical reflectors in a second predetermined pattern on the surface proximate the plate; and

[0050] A first end of an S-shaped mounting arm is connected to the radiolucent plate, the arm having a second end including one or more fastening sockets.

[0051] According to an embodiment of the present invention, a method is further provided, comprising:

[0052] attaching a surgical clamp to the patient's bone;

[0053] embedding a first plurality of radiopaque elements arranged in a first predetermined pattern in a radiolucent plate and positioning a second plurality of optical reflectors in a second predetermined pattern on a surface proximate the plate;

[0054] connecting a first end of an S-shaped mounting arm to the surgical clamp, the arm having a second end fixedly connected to the radiolucent plate;

[0055] fluoroscopically scanning the radiolucent plate, the S-mounting arm, and the surgical fixture to form a fluoroscopic scan;

[0056] optically scanning the second plurality of optical reflectors to form a first optical scan;

[0057] disconnecting the first end of the S-shaped mounting arm from the surgical clamp and connecting a patient marker to the surgical clamp, the patient marker having a third plurality of reflectors in a third predetermined pattern;

[0058] optically scanning a third plurality of optical reflectors to form a second optical scan;

[0059] deriving a correction vector from the first optical scan and the second optical scan, the correction vector indicating a difference between a position and orientation of the radiolucent plate and a position and orientation of a patient marker; and

[0060] A spatial transformation between the patient and the surgical jig is determined in response to the correction vectors and the fluoroscopic scan to register the patient's frame of reference with the surgical jig's frame of reference.

[0061] Typically, the method includes, responsive to registering the reference frame, presenting a stored image of the patient aligned with the patient to a professional performing surgery on the patient.

[0062] The present disclosure will be more fully understood from the following detailed description of embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 is a schematic diagram illustrating a medical marking device used in preparation for a medical procedure according to an embodiment of the present invention;

[0065] Figure 2 is a schematic diagram of a device separated from a clamp according to an embodiment of the present invention;

[0066] Figure 3 is a schematic exploded view of the device according to an embodiment of the present invention.

[0067] Figure 4 is a flow chart of steps performed in both the preparation phase and the subsequent phase of a program according to an embodiment of the present invention;

[0068] Figure 5 is a schematic diagram of subsequent stages of a procedure according to an embodiment of the present invention; and

[0069] Figure 6 、 Figure 7 and Figure 8 is a schematic diagram of a medical marking device according to an alternative embodiment of the present invention. DETAILED DESCRIPTION

[0070] Overview

[0071] Embodiments of the present invention provide fiducial markers for registering different reference frames present during image-guided surgery on a patient. Image-guided surgery can be performed by a medical professional wearing an augmented reality head-mounted display, and for the display to operate correctly, the patient image presented to the professional must be aligned with the actual patient. The registration provided by the fiducial markers ensures the necessary image alignment.

[0072] In the disclosed embodiments, the markers are attached to a jig that has been attached to one or more spinous processes of the patient in preparation for the procedure. To accommodate physical differences between patients, embodiments of the present invention provide an optional system for attaching fiducial markers to the jig, including fixed-width and variable-width spacers that connect the markers to the jig.

[0073] The fiducial markers include radiopaque elements arranged in a predetermined pattern so that the markers and a computed tomography (CT) image of the patient can be registered in preparation for registering the reference frame of the patient's anatomy with the reference frame of the fixture.

[0074] At a later stage in the procedure, the fiducial markers are replaced by patient markers.In some embodiments of the invention, the fiducial markers further comprise optical reflectors, and images of these reflectors can be used to accommodate different positions of the patient markers.

[0075] The registration obtained in the preparation phase is used in subsequent phases of the procedure so that the images of the patient's markers are used to track the patient and ensure that the images presented to the professional are correctly aligned.

[0076] This CT facility typically includes an intraoperative CT scanner with a narrow field of view, so for successful registration, the radiopaque element of the fiducial marker and the vertebral body should be close together. Embodiments of the present invention achieve this close proximity by providing the fiducial marker in the form of a "step," where one portion of the step comprises a plate containing the radiopaque element, and the stepped form of the fiducial marker enables the plate to be positioned close to the vertebral body. The second portion of the step is attached to the fixture, and there is a known mechanical offset between the two portions.

[0077] In an embodiment of the present invention, the plate is radiolucent and has the aforementioned plurality of radiopaque elements embedded therein in a predetermined pattern. To achieve the aforementioned stepped form, a first end of an S-shaped mounting arm is fixedly connected to the radiolucent plate. Furthermore, the S-shaped mounting arm has a second end containing one or more fastening receptacles configured to removably connect the arm to a clamp attached to the spinous process.

[0078] In the disclosed embodiment, the radiolucent plate, the S-shaped mounting arm, and the surgical clamp are fluoroscopically scanned to form a fluoroscopic scan. In response to the fluoroscopic scan and a predetermined mechanical offset, a spatial transformation between the patient and the surgical clamp is determined to align the patient's reference frame with the surgical clamp's reference frame.

[0079] Typically, in response to the registration of the reference frames, a stored image of the patient aligned with the patient is presented to a professional performing the procedure on the patient.

[0080] System Description

[0081] Hereinafter, all directional references (e.g., up, down, upward, downward, left, right, top, bottom, above, below, vertical, and horizontal) are used only for identification purposes to help the reader understand the present invention and do not create limitations, especially no limitations on the position, orientation, or use of embodiments of the present invention.

[0082] Now refer to Figure 1 , Figure 1 is a schematic diagram illustrating a medical marker device 10 used during the preparatory phase of a medical procedure on a patient 20, according to an embodiment of the present invention. The procedure referred to herein is assumed to include a preparatory phase and a subsequent phase, and as described in more detail below, the device 10 can be used during the preparatory phase. The device 10 is also referred to herein as a fiducial marker 10. Furthermore, as described below, the medical professional uses an augmented reality system during the subsequent phase of the procedure.

[0083] The augmented reality system projects virtual images of various elements of the patient 20 for observation by the medical professional. Image projection occurs simultaneously with the professional's observation of the actual patient, so the projected image should be aligned with the patient. To align the projected image in the augmented reality system with the patient, a marking device 10 is used during the preparatory phase to align the patient's reference frame with the reference frame of the jig attached to the patient's anatomy. The jig registration calculated during the preparatory phase is used to correctly align the images generated by the system during subsequent use of the augmented reality system.

[0084] In the description herein, a procedure is assumed to include manipulation of the spine of a patient 20, and to perform the aforementioned registration prior to the procedure and in preparation for the procedure, a medical professional inserts a surgical bone jig 24 into the patient 20. The jig's insertion site 28 is proximal to, but separate from, a site 32 of the patient's spine that will be manipulated during a subsequent stage of the procedure. The professional clamps the jig 24 about a section of the patient's spine, typically about one or more of the patient's spinous processes, and the jig has a support structure 36 to which the marker 10 is secured. A jig similar to the jig 24 is described in U.S. patent application Ser. No. 16 / 120,480, which is incorporated herein by reference.

[0085] Figure 2 is a schematic diagram of the apparatus 10 separated from the fixture 24, and Figure 3is a schematic exploded view of a device 10 according to an embodiment of the present invention. Device 10 includes a radiolucent plate 50, typically formed from a biocompatible plastic such as polyimide. Embedded within plate 50 are a plurality of substantially similar radiopaque elements 54, which are herein assumed to comprise spheres. Elements 54 are embedded within plate 50 in a predetermined pattern, which is herein assumed to comprise points on the sides of a rectangle. However, any other convenient predetermined pattern may be used. In some embodiments, the predetermined pattern lacks an axis or plane of symmetry. Plate 50 is typically protected by a cover 52.

[0086] A radiolucent S-shaped mounting arm 58, typically formed of the same biocompatible plastic as the plate 50, is connected to the edge 66 of the plate by a first end 62 of the arm. A second end 70 of the arm contains one or more fastening receptacles 74 that enable the arm to be securely and fixedly fastened to the support structure 36 in a predetermined orientation. In an embodiment of the present invention, the support structure 36 encloses an adjustment element 102 for the clamp 24 that enables attachment of the jaws of the clamp to the bone of the patient 20. In an embodiment of the present invention, the support structure has different depths d.

[0087] Second end 70 has a lower planar surface 78 that connects to upper surface 82 of support structure 36. In the disclosed embodiment, socket 74 includes a captive screw 86 and a hole 92 that mate with a threaded hole 96 in upper surface 82 and a post 100, respectively.

[0088] As is apparent from the figure, the length of the arm 58 determines the spacing of the plate 50 from the lower surface 78 of the second end of the arm. Embodiments of the present invention include multiple groups of apparatus 10, each member in a group being substantially as described herein, but having a known arm 58 length that is different from that of the other group members. The arm 58 is formed by two curved sections 112, 116 separated by a straight section 120, and arms of different lengths are formed by varying the length of the straight section 120. In embodiments of the present invention, the length of the straight section 120 varies from 0 (zero) to approximately 7 cm, although values ​​greater than 7 cm are possible. It should be understood that when the length of the section 120 is 0, the two curved sections are connected together without an intermediate straight section.

[0089] Each member of the set includes a respective plate 50 connected in a stepped arrangement to a respective S-shaped mounting arm 58, typically formed as a single piece by injection molding. It will be appreciated that each member of the set has known dimensions such that there is a known mechanical offset between the plate 50 and the second end of the arm (including the lower surface 78 of the second end of the arm).

[0090] Typically, for each component of a set of devices 10, the predetermined pattern of radiopaque elements 54 is configured to have a one-to-one correspondence with a known mechanical offset. In this case, identification of the pattern provides a unique and unambiguous value for the mechanical offset, and providing this correspondence enables embodiments of the present invention to support substantially any offset. As described below, this correspondence can be stored in a computer memory and accessed so that a unique value for the mechanical offset of a component of a given set can be determined based on the element pattern of that component.

[0091] In addition to the groups of apparatuses 10 described above, embodiments of the present invention also include groups of clamps 24 in which the support structures 36 have different depths d. It will be appreciated that for any given arm length 58, the depth d of the support structure 36 determines the spacing of the plate 50 from a given clamp selected from the group of clamps 24.

[0092] Back to Figure 1 , the device 10 is typically selected from a group of devices 10, and the clamp 24 is typically selected from a group of clamps 24 so that when the device is attached to the upper surface 82 of the support structure 36, the plate 50 of the device is as close as possible to the site 32, that is, close to the site where the operation will be performed in the subsequent stages of the procedure. Once the selected device 10 has been attached to the surface 82, a computed tomography (CT) scan of the device and the patient's spine is performed. The scan can be performed by embedding the patient 20 in a CT scanning facility, which is typically an intraoperative CT scanner. The embedding can be implemented by bringing the CT scanning facility to the patient 20, or by transporting the patient to the facility.

[0093] A processing system 104, including a computer processor 108 coupled to a memory 114, receives a scan of the device 10 and the patient's spine and stores the scan in the memory as an image 118. The one-to-one correspondences mentioned above may also be stored in the memory 114 as correspondences 122. The processing system is configured to analyze the stored images to identify the pattern formed by the radiopaque element 54 and, from the identified pattern, to register the frame of reference of the device 10, and thus the attached clamp 24, with the frame of reference of the patient's anatomy.

[0094] Figure 4 FIG2 is a flow chart of steps performed in both the preparation phase and the subsequent phase of a procedure according to an embodiment of the present invention. In the initial step 150 and the attachment step 152 of the preparation phase, the clamp 24 is inserted into the patient 20 and one or more spinous processes of the patient are clamped using the adjustment element 102, and the fiducial marker 10 is attached to the support structure 36 of the clamp, as described above with reference to FIG2. Figure 1 As stated.

[0095] In a scanning step 154, a CT scan is performed on the marker 10 attached as described above, and an image 118 of the scan is stored in the memory 114. In an analyzing step 156, the processing system analyzes the stored image and, based on the analysis, registers the frame of reference of the marker 10, and therefore the attached clamp 24, with the frame of reference of the patient's anatomy.

[0096] It should be understood that the registration in step 156 utilizes the known mechanical offset of the plate 50 from the lower surface 78 to provide the position and orientation of the upper surface 82 of the fixture relative to the reference frame of the patient's anatomy. In the case where the one-to-one correspondence mentioned above is stored in the memory 114 as the correspondence 122, the processing system can use this stored correspondence in the analysis step 156 to determine the mechanical offset by analyzing the identified pattern.

[0097] The analysis step 156 also determines the spatial transformation between the patient and the surgical fixture, and this, along with the mechanical offset, is used to calculate the registration between the two reference frames.

[0098] In a concluding step 158 of the preparation phase, the fiducial marker 10 is removed from the fixture 24 , leaving the upper surface 82 exposed.

[0099] Figure 5 1 is a schematic diagram of a subsequent stage of a procedure, according to an embodiment of the present invention. In the subsequent stage, a patient marker attachment step 160 and an alignment step 162 are performed, and these steps are further described below. In the subsequent stage, a medical professional 180 performs a procedure on the patient. The professional 180 wears an augmented reality head-mounted display (HMD) 184, which is configured to present the professional with a stored image aligned with the patient. For operation, the HMD 184 is coupled to the processor 108 of the system 104, and the stored images can be stored in the memory 114. Optionally, the HMD 184 has its own dedicated processor that performs functions similar to those performed by the processor 108. U.S. Patent 9,928,629, which is incorporated herein by reference, describes a head-mounted display similar to the HMD 184.

[0100] To perform alignment of the HMD 184, a patient marker 190 having known preset dimensions is attached to the upper surface 82 of the support structure 36 of the fixture 24 in an attachment step 160. The marker 190 includes a fastening receptacle 198, substantially similar to the receptacle 74, and thus, in the above-disclosed embodiment mentioned above, the receptacle 198 includes a captive screw 202 and a hole 206 that mate with the threaded hole 96 and the post 100, respectively, in the upper surface 82 of the fixture 24. A patient marker similar to the marker 190 is described in PCT patent application PCT / IB2019 / 053524, which is incorporated herein by reference.

[0101] The marker 190 includes optical reflectors 194 bonded to the surface of the patient marker, and the reflectors are arranged in a predetermined pattern so that images of the reflectors can be analyzed to provide an unambiguous measurement of the position and orientation of the marker.

[0102] In an alignment step 162, the HMD projects visible or invisible light onto the patient marker 190 and acquires an image of the marker's reflector 194. Based on the acquired image, the HMD processor determines the position and orientation of the patient marker. Since the patient marker has known dimensions and is attached to the upper surface 82, the processor applies the registration obtained in step 156 (between the reference frame of the fiducial marker 10 and the reference frame of the patient's anatomy) to ensure that the image projected by the HMD is aligned with the anatomy of the patient 20.

[0103] The above description provides details of how the fiducial marker 10 and the patient marker 190 can be attached as close as possible to the site 32 (i.e., the site of the procedure being performed on the patient 20) by the clamp 24. The following description provides further details of embodiments of the present invention that can alternatively or additionally be used to bring the patient marker and the fiducial marker as close as possible to the site of the procedure.

[0104] Figure 6 2 is a schematic diagram of a medical marking device 250 separated from the clamp 24 according to an alternative embodiment of the present invention. The operation of the device 250 is generally similar to that of the device 10 ( Figure 1-5 ) and elements indicated by the same reference numerals in both devices 250 and 10 are generally similar in structure and operation. Device 250 is also referred to herein as fiducial marker 250.

[0105] In contrast to device 10, in which the second end 70 of the S-shaped arm is configured to connect directly to the upper surface 82 of the support structure 36, in device 250, an intermediate spacer 254 is present between the second end of the S-shaped arm and the surface 82. Spacer 254 is formed to have a pair of opposing parallel surfaces, namely, an upper spacer surface 258 and a lower spacer surface 262, which are separated by a predetermined fixed distance h. When assembled, lower surface 262 is fixedly engaged with upper surface 82 of support structure 36, and lower surface 78 of the S-shaped arm is removably engaged with upper surface 258 of spacer 254.

[0106] To allow the lower spacer surface 262 to securely engage the surface 82 of the support structure, the lower spacer surface has two blind holes 266 therein that align with and mate with the posts 100. Furthermore, the spacer 254 includes a captive screw 270 positioned within a hole 274 in the spacer. The captive screw is configured so that when it is threaded into the threaded hole 96, it securely secures the spacer to the support structure 36 with the head of the screw 270 within the hole 274 and below the upper surface 258 of the spacer. The captive screw 270 and the blind hole 266 serve as a spacer lower surface securing receptacle 290.

[0107] Once the spacer 254 is secured to the support structure 36, the lower surface 78 of the S-shaped arm can be removably engaged with the upper surface of the spacer. The upper surface of the spacer includes two threaded holes 278 that align with the holes 92. To removably engage the lower surface of the S-shaped arm with the spacer, a pair of retaining screws 282 are passed through the holes 92 and threaded into the threaded holes 278. The screws 282 and threaded holes 278 serve as fastening receptacles 294 for the upper surface of the spacer.

[0108] Typically, the spacer 254 is part of a set of such spacers. In one embodiment, the set of spacers has an h value in the range of 1 cm to 5 cm, but in other embodiments, the set of spacers has a different range of h values. The spacers 254 are used to elevate the plate 50 above the clamp 24 while keeping the plate as close to the patient's spine as possible, and the h value of the selected spacer can be selected based on the patient's characteristics. It should be understood that having a set of spacers 254 with different h values ​​replaces or supplements the above-mentioned requirement for a set of arms 58 of different lengths for the device 10.

[0109] In a procedure using the marker 250, as described above, after the marker 250 is attached to the upper surface of the spacer 254, it can be scanned fluoroscopically and then removed from the upper surface of the spacer. Figure 6As shown, after removal, the patient marker 190 can then be attached to the upper surface of the spacer. The patient marker is attached by a screw 302, which is substantially similar to the screw 282, passing through the hole 206 and screwing into the threaded hole 278. The screw 302 and the threaded hole 278 serve as a fastening socket 298 for the patient marker, which is substantially similar to the socket 294.

[0110] Return Reference Figure 4 When the marker 250 is used instead of the marker 10, the actions described above for each step of the flowchart are substantially similar, except as follows.

[0111] In step 152 , the spacer 254 is first fixedly attached to the support structure 36 , and then the fiducial marker 250 is removably attached to the spacer, as described above.

[0112] As described above, in step 158 , the fiducial marker 250 is removed from the spacer, and in step 160 , the patient marker 190 is attached to the spacer.

[0113] It should be appreciated that because the fiducial marker 250 and the patient marker 190 are attached at the same location, ie, the upper surface of the spacer, the registration established in step 156 may be used in the alignment step 162 .

[0114] Figure 7 2 is a schematic diagram of a medical marking device 350 separated from the clamp 24 according to an alternative embodiment of the present invention. The operation of the device 350 is generally similar to that of the device 250 ( Figure 1-6 ) and elements indicated by the same reference numerals in both devices 250 and 350 are generally similar in structure and operation. Device 350 is also referred to herein as fiducial marker 350.

[0115] In contrast to device 250, which utilizes spacer 254 having a preset fixed distance between its upper and lower surfaces, device 350 utilizes spacer 354, also referred to herein as adjustable spacer 354, having an adjustable distance between an upper adjustable spacer plate 358 and a lower adjustable spacer plate 362. The elements in the two plates of adjustable spacer 354 correspond to corresponding elements in the two surfaces of fixed spacer 254. Thus, in upper plate 358, threaded hole 378 and hole 374 are substantially similar to holes 278 and 274, such that hole 374 allows passage of captive screw 270. Screw 282 and threaded hole 378 serve as fastening receptacle 394 for the upper adjustable spacer plate.

[0116] In lower plate 362, hole 366 has a diameter and location substantially similar to blind hole 266, although hole 366 need not be a blind hole. Lower plate 362 also includes hole 374A, which is aligned with hole 374 and is sized to retain screw 270. Captive screw 270 and hole 366 serve as a fastening receptacle 390 for the lower adjustable spacer plate.

[0117] The adjustable spacer 354 includes an adjustable mechanism 400 that connects the lower and upper plates of the adjustable spacer 354. The mechanism 400 maintains the upper plates substantially parallel to each other while operating the mechanism to adjust the spacing of the plates.

[0118] In one embodiment, Figure 7 As shown, the mechanism 400 includes a rod 404 having clockwise and counterclockwise threads, and the threads are configured to mate with corresponding nuts 408, 412 that are slidingly attached to the upper plate 358. The mechanism 400 also includes two levers 416, 420, whose fulcrums are coupled to the lower plate 362 and whose endpoints are attached to corresponding nuts. Rotation of the rod 404 of the mechanism 400 increases or decreases the nut spacing and, accordingly, decreases or increases the spacing between the upper and lower plates of the adjustable spacer 354.

[0119] Other mechanisms for connecting the upper and lower plates of the spacer 354 that provide adjustable plate spacing while maintaining the plates substantially parallel to each other will be apparent to those skilled in the art. All such mechanisms are considered to be within the scope of the present invention.

[0120] Return Reference Figure 4 Flowchart of, when marker 350 is used instead of marker 10, the actions described above for each step of the flowchart are substantially similar, except as follows.

[0121] In step 152 , the lower plate 362 is first fixedly attached to the support structure 36 , and then the fiducial marker 350 is removably attached to the upper plate 358 , as described above.

[0122] As described above, in step 158 , the fiducial markers 350 are removed from the upper plate 358 of the spacer, and in step 160 , the patient markers 190 are attached to the upper plate of the spacer.

[0123] It should be appreciated that because the fiducial marker 350 and the patient marker 190 are attached at the same location, namely the upper surface of the upper plate of the spacer, the registration established in step 156 can be used in the alignment step 162 .

[0124] Figure 82 is a schematic diagram of a medical marking device 450 separated from the clamp 24 according to an alternative embodiment of the present invention. The operation of the device 450 is generally similar to that of the device 250 except for the differences described below. Figure 1-6 ), and elements indicated by the same reference numerals in both devices 250 and 450 are generally similar in structure and operation. Device 450 is also referred to herein as fiducial marker 450.

[0125] In contrast to the device 250, a plurality of optical reflectors 454 are located on the surface 458 of the cover 52 of the plate 50. In one embodiment, the reflectors 454 are arranged on the surface in a predetermined pattern, typically having no rotational symmetry axis (except for a common symmetry axis of 360° rotation) and no symmetrical mirror surfaces. The predetermined pattern is configured so that the image of the reflectors can be analyzed to provide an unambiguous measurement of the position and orientation of the plate 50. Imaging of the reflectors 454 and analysis of the image are substantially the same as described above for the reflectors 194 of the patient markers 190.

[0126] Device 450 is typically used with spacer 254 and / or spacer 354, as described above with reference to Figure 6 and Figure 7 When the device 450 is used with one of these spacers, the patient marker 190 can be positioned relative to the spacer as described above. However, due to the presence of the reflector 454, the patient marker 190 can alternatively be positioned in any other convenient location, as described below with reference to Figure 4 The changes in the flowchart are explained.

[0127] For clarity, in the following description of the changes to the flowchart, it is assumed that the apparatus 450 is used with the spacer 254. A person skilled in the art will be able to adapt this description mutatis mutandis if the apparatus 450 is used with the spacer 354 or any other spacer that effectively separates the plate 50 from the support structure 36.

[0128] In step 152 of the flowchart, the spacer 254 is first attached to the support structure 36 using screws 270 and then the fiducial marker 450 is attached to the spacer using screws 282 as described above.

[0129] Steps 154 and 156 are as above. Figure 4 This is performed as described so as to register the frame of reference of the marker 450, and therefore the frame of reference of the attached clamp 24, with the frame of reference of the patient anatomy.

[0130] In step 158, before removing the fiducial marker 450 from the spacer, the marker's reflector 454 is optically scanned and imaged using the HMD 184. A processor associated with the HMD 184 analyzes the image to find the position and orientation of the reflector in the HMD reference frame, thereby finding the position and orientation of the plate 50. The marker 450 can then be removed from the spacer 254, and the spacer can be removed from the support structure 36.

[0131] Steps 160 and 162 are performed generally as described above, such that in step 160 , the patient marker 190 is attached to the upper surface 82 of the support structure 36 .

[0132] In step 162, the patient markers 190 are optically scanned and tracked, and the processor of the HMD can use the position and orientation of the plate 50 found in step 158 to generate a correction vector between the position of the plate and the position of the patient markers. The correction vector corrects for the fact that the fiducial markers and the patient markers are attached in different locations (i.e., the spacer and the support structure). In step 162, the HMD processor applies the correction vector to ensure that the image projected by the HMD is aligned with the anatomy of the patient 20.

[0133] The above description is directed to the specific case of patient markers 190 and fiducial markers 450 being attached to different elements associated with the clamp 24. Those skilled in the art will be able to make the necessary modifications for other different attachment scenarios, and all such scenarios are considered to be within the scope of the present invention.

[0134] It will be appreciated that the embodiments described above are listed by way of example only, and the present invention is not limited to those that have been particularly shown and described hereinabove. Rather, the scope of the present invention includes combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that would occur to those skilled in the art upon reading the foregoing description and that are not disclosed in the prior art.

Claims

1. A medical marking device comprising: a radiolucent plate comprising a plurality of radiopaque elements embedded in the radiolucent plate in a predetermined pattern; an S-shaped mounting arm having a first end connected to the radiolucent plate and a second end including one or more fastening sockets, wherein the S-shaped mounting arm is configured to position the first end and the radiolucent plate closer to a operative site to be performed on the patient than the second end; and a spacer having a first surface and a second surface, the second surface being configured to be fixedly coupled to a surgical clamp, wherein the surgical clamp is configured to be attached to a bone of a patient; Wherein, the first surface includes a first plate and the second surface includes a second plate, the medical marking device further includes an adjustable mechanism connecting the first plate to the second plate, and the adjustable mechanism is configured to adjust the spacing between the first plate and the second plate.

2. The medical marking device according to claim 1, wherein: The S-shaped mounting arm is radiolucent.

3. The medical marking device according to claim 1, wherein: The S-shaped mounting arm includes a first curved section connected to a second curved section by a straight section.

4. The medical marking device according to claim 1, wherein: The S-shaped mounting arm includes a first curved section directly connected to a second curved section.

5. The medical marking device according to claim 1, wherein: The predetermined pattern has no axis of symmetry and no plane of symmetry.

6. The medical marking device according to claim 1, wherein: The radiolucent plate further comprises a plurality of optical reflectors positioned in an additional predetermined pattern on a surface of the radiolucent plate, and wherein the additional predetermined pattern is configured to allow unambiguous measurement of the position and orientation of the radiolucent plate.

7. The medical marking device according to claim 1, wherein: The operation site is a site of the patient's spine.

8. The medical marking device according to claim 1, wherein: The S-shaped mounting arms of each medical marking device in a set of the medical marking devices have different lengths.

9. The medical marking device according to claim 8, wherein: The predetermined pattern of the plurality of radiopaque elements of each medical marking device in a set of the medical marking devices is configured to have a one-to-one correspondence with a length of the S-shaped mounting arm of each medical marking device.

10. The medical marking device according to any one of claims 1 to 7, wherein: The one or more fastening receptacles are configured to movably connect the S-shaped mounting arm to the first surface of the spacer.

11. The medical marking device according to any one of claims 1 to 7, wherein: The surgical clamp includes a support structure; and Wherein, the one or more fastening sockets are configured for removable connection of the S-shaped mounting arm to the support structure.

12. The medical marking device according to claim 11, wherein: The surgical clamp includes a clamp adjustment element configured to achieve the attachment, and wherein the support structure surrounds the clamp adjustment element.

13. The medical marking device according to claim 11, wherein: The surgical clips include a set of surgical clips, and wherein the support structures of the surgical clips in the set of surgical clips have different depths.

14. The medical marking device according to claim 1, wherein: The medical marking device has a stepped form.

15. The medical marking device according to claim 1, wherein: The medical marking device has a known mechanical offset between the radiolucent plate and a lower surface of the second end of the S-shaped mounting arm.

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