Robotic fluoroscopic navigation

Abstract

To provide systems and methods for an improved registration fixture.SOLUTION: A registration fixture 2 includes a base frame 6 adapted to be mounted on a flat panel detector of an x-ray medical imaging device, and a side frame 8 having optical tracking markers mounted on the base frame. The base frame includes a first set of radiopaque markers embedded therein in a first predetermined pattern and arranged on a plane, and a second set of radiopaque markers embedded therein in a second predetermined pattern and also arranged on another plane, which is separated from the first set of radiopaque markers. The side frame has a plurality of optical tracking markers and is configured to be detachably mounted on the base frame without piercing a sterilizing drape to be interposed between the base frame and the side frame.SELECTED DRAWING: Figure 38

Description

[Technical field]

[0001] The present disclosure relates to position aware systems, and more particularly to registering medical images to a three-dimensional tracking space. [Background technology]

[0002] Orthopedic navigation has the potential to improve patient outcomes through reduced blood loss, radiation dose, and procedure and anesthesia times, in addition to increasing the precision and ease with which complex procedures can be performed. Two surgical navigation workflows for achieving these improved outcomes are fluoroscopy and preoperative navigation workflows, which require a C-arm imaging device and a fluoroscopy registration fixture.

[0003] Conventionally, the alignment fixture is attached to the X-ray transmitter side. However, in some cases, this is an inaccurate way to align the navigation system, and certain transmitter housing shapes may cause problems in mounting the fixture. Therefore, it is desirable to provide a system and method for an improved alignment fixture. Summary of the Invention

[0004] According to one aspect of the invention, there is provided a registration fixture for use with a surgical navigation system to register medical images in a three-dimensional tracking space. The registration fixture includes a base frame adapted to be mounted on a flat panel detector of an x-ray medical imaging device and a side frame having optical tracking markers attached to the base frame. The base frame includes a first set of radiopaque markers embedded therein in a first predetermined pattern and a second set of radiopaque markers embedded therein in a second predetermined pattern spaced vertically from the first set of radiopaque markers. The side frame has a plurality of optical tracking markers and is configured to be removably attached to the base frame without penetrating a sterile drape inserted between the base frame and the side frame.

[0005] These and other systems, methods, objects, features, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments and the drawings, all of which are incorporated herein by reference in their entirety. [Brief description of the drawings]

[0006] The present invention and the following detailed description of certain embodiments thereof can be understood by reference to the following drawings. [Figure 1] 1A-1C are overhead views of potential configurations of the robotic system, the patient, the surgeon, and the locations of other medical personnel during a surgical procedure. [Diagram 2] 1 illustrates a robotic system including a surgical robot and camera positioning relative to a patient according to one embodiment. [Diagram 3] 1 illustrates a surgical robotic system according to an exemplary embodiment. [Figure 4] 1 illustrates a portion of a surgical robot according to an exemplary embodiment. [Diagram 5] FIG. 1 illustrates a block diagram of a surgical robot in accordance with an illustrative embodiment. [Figure 6]1 illustrates a surgical robot according to an exemplary embodiment. [Figure 7A] 1 illustrates an end effector in accordance with an illustrative embodiment. [Figure 7B] 1 illustrates an end effector in accordance with an illustrative embodiment. [Figure 7C] 1 illustrates an end effector in accordance with an illustrative embodiment. [Figure 8] 1 illustrates a surgical instrument and an end effector before and after insertion of the surgical instrument into a guide tube of the end effector, according to one embodiment. [Figure 9A] 1 is an illustration of an end effector and portion of a robotic arm in accordance with an illustrative embodiment; [Figure 9B] 1 is an illustration of an end effector and portion of a robotic arm in accordance with an illustrative embodiment; [Figure 9C] 1 is an illustration of an end effector and portion of a robotic arm in accordance with an illustrative embodiment; [Figure 10] 1 illustrates a dynamic reference array, an imaging array, and other components, according to an example embodiment. [Figure 11] 1 illustrates a method for alignment in accordance with an illustrative embodiment; [Figure 12A] 1 illustrates an embodiment of an imaging device in accordance with an exemplary embodiment. [Figure 12B] 1 illustrates an embodiment of an imaging device in accordance with an exemplary embodiment. [Figure 13] 1 illustrates one embodiment of a navigation fixture. [Figure 14] An X-ray (fluoroscopy) collector plate is shown showing theoretical projections of a small metal sphere (hereafter referred to as "BB") in two planes at different distances from the source. [Figure 15] Shown are two x-ray projections taken of the same radiopaque point from two different perspectives to generate a 3D location. [Figure 16] An X-ray image taken through a plane parallel to the collector plate of the BB grid is shown. [Figure 17]The major dimensions are shown looking at a plane perpendicular to the plane of the collector plate, with BB in the field of view and its shadow appearing on the collector plate. [Figure 18] Shown is the bb pattern on two parallel plates and the design of the fixture that is attached to the image intensifier of the fluoroscopy unit. [Figure 19] The BB pattern of the alignment fixture is shown. [Figure 20] 1 shows a fluoroscopy registration fixture composed of parallel rings with crosshairs. [Figure 21] FIG. 1 shows the appearance of the ring alignment fixture on an x-ray when the x-ray collector is parallel to the plane of the ring and the ring is concentric with the x-ray collector. [Figure 22] 1 shows the theoretical appearance of the ring alignment fixture on an x-ray when the fixture is at a steep angle to the collector plate and ring. [Diagram 23] 1 illustrates the transformation step of rotating by θ about z in the coordinate system mapping process. [Figure 24] 4 shows the transformation step of rotating by α about y in the coordinate system mapping process. [Diagram 25] 13 illustrates the in-plane rotation transformation step in the coordinate system mapping process to match the radiograph viewpoint. [Figure 26] This shows the transformation step in the coordinate system mapping process, which displaces the coordinate system center by dx, dy. [Figure 27] 1 illustrates the parallax-scale transformation step in the coordinate system mapping process. [Figure 28] The major dimensions are shown generally as viewed in a plane perpendicular to the plane of the collector plate, with a ring parallel to the collector being in the field of view and its shadow appearing on the collector plate. [Figure 29] A view is shown across the ring at an arbitrary angle of incidence to the collector plane from a perspective looking across the ring plane, with the ring plane lying in and out of the page. [Diagram 30]A view is shown across a pair of concentric rings at an arbitrary angle of incidence to the collector plane, from a perspective looking across the ring plane, with the ring plane lying in and out of the page. [Diagram 31] A diagram of the ring at an arbitrary angle of incidence from a rotated viewpoint is shown. [Diagram 32] A diagram of a pair of rings at an arbitrary angle of incidence is shown. [Diagram 33] Shown is the modeled appearance on an X-ray (with parallax) of two circular rings with an angle of incidence of α=20° originating about the y-axis. [Diagram 34] Shown is the modeled appearance on an x-ray (with parallax) of two parallel circular rings with an angle of incidence of α=24.5° originating about the y-axis, both rings being offset from the x-ray center and the major axes of both ellipses appearing to be visually at an angle to the y-axis. [Diagram 35] 1 shows the modeled appearance on an x-ray (with parallax) of two parallel circular rings with an incidence angle of α=24.5° occurring about the y-axis, both rings are offset from the x-ray center, and the far-field ellipse is scaled about the center of the image until the near-field and far-field ellipses are equal in their major axes. [Diagram 36] Shows pincushion distortion. [Figure 37] Shows s-shaped distortion. [Figure 38] 1 is a perspective view of a novel alignment fixture designed to be mounted to a flat panel detector of a medical imaging device, in accordance with one aspect of the present invention; [Figure 39] FIG. 2 is a plan view of a radiolucent plate having two sets of vertically spaced embedded radiopaque markers according to one embodiment of the present invention. [Figure 40A] FIG. 40 is a plan view of a first plate of the radiolucent plate of FIG. 39 with a predetermined pattern of radiopaque markers. [Figure 40B]FIG. 40 is a plan view of a second plate of the radiolucent plate of FIG. 39 with a predetermined pattern of radiopaque markers. [Diagram 41] FIG. 40 is a perspective view of the base frame and side frames of the alignment fixture of FIG. 38 prior to assembly. [Diagram 42] FIG. 42 is a side view of the kinematic mount of the side frame of FIG. 41 showing the non-penetrating clamp. [Figure 43A] FIG. 39 is an outer perspective view of an alternative non-penetrating kinematic clamp of the alignment fixture of FIG. 38. [Figure 43B] FIG. 39 is an outer perspective view of an alternative non-penetrating kinematic clamp of the alignment fixture of FIG. 38. [Diagram 44] FIG. 43B is a cross-sectional view of the side frame of FIG. 43A. [Diagram 45] FIG. 39 is a perspective view of the base frame of FIG. 38 having a set of straps and ratchets for mounting to a flat panel detector. [Figure 46] 46 shows the base frame of FIG. 38 attached to a flat panel detector using straps and ratchets as shown in FIG. 45.

[0007] Although the invention has been described in connection with certain preferred embodiments, other embodiments will be understood by those of skill in the art and are encompassed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components described in the description herein or illustrated in the drawings. The teachings of the present disclosure can be used and implemented in other embodiments and can be practiced or carried out in various ways. It is also to be understood that the phraseology and terminology used herein is for the purpose of description and should not be considered as limiting. The use of "including," "comprising," or "having," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items. Unless otherwise specified or limited, terms such as "mounted," "connected," "supported," and "coupled," and variations thereof, are used broadly and encompass both direct and indirect mounting, connecting, supporting, and coupling. Moreover, "connected" and "coupled" are not limited to physical or mechanical connections or couplings.

[0009] The following discussion is presented to enable those skilled in the art to make and use the embodiments of the present disclosure. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the principles of the present disclosure may be applied to other embodiments and applications without departing from the embodiments of the present disclosure. Thus, the embodiments are not intended to be limited to the embodiments shown, but should be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description should be read with reference to the drawings, in which like elements in different drawings have like reference numerals. The figures are not necessarily to scale, depict selected embodiments, and are not intended to limit the scope of the embodiments. Those skilled in the art will recognize that the examples provided herein have many useful alternatives and are within the scope of the embodiments.

[0010] 1 and 2 show a surgical robotic system 100 according to an exemplary embodiment. The surgical robotic system 100 may include, for example, a surgical robot 102, one or more robotic arms 104, a base 106, a display 110, an end effector 112 including, for example, a guide tube 114, and one or more tracking markers 118. The surgical robotic system 100 may include a patient tracking device 116 that also includes one or more tracking markers 118 adapted to be fixed directly to a patient 210 (e.g., to a bone of the patient 210). The surgical robotic system 100 may also utilize a camera 200 positioned, for example, on a camera stand 202. The camera stand 202 may have any suitable configuration for moving, orienting, and supporting the camera 200 in a desired position. The camera 200 may include any suitable camera(s), such as one or more infrared cameras (e.g., bifocal or stereo photogrammetry cameras), and may, for example, identify active and passive tracking markers 118 in a given measurement volume visible from the viewpoint of the camera 200. The camera 200 may scan the given measurement volume and detect light originating from the markers 118 to identify and determine the position of the markers 118 in three dimensions. For example, the active markers 118 may include infrared emitting markers that are activated by an electrical signal (e.g., an infrared light emitting diode (LED)), and the passive markers 118 may include retro-reflective markers that reflect infrared light emitted by an illuminator on the camera 200 or other suitable device (e.g., reflect incident IR radiation in the direction of the incident light).

[0011] 1 and 2 illustrate potential configurations for placement of the surgical robotic system 100 in an operating room environment. For example, the robot 102 may be positioned near or next to the patient 210. Although shown near the head of the patient 210, it will be understood that the robot 102 may be positioned in any suitable location near the patient 210 depending on the area of ​​the patient 210 undergoing surgery. The camera 200 may be separate from the robotic system 100 and positioned at the feet of the patient 210. This location allows the camera 200 to have a direct line of sight to the surgical field 208. Again, it is contemplated that the camera 200 may be positioned in any suitable location having a line of sight to the surgical field 208. In the illustrated configuration, the surgeon 120 may be positioned across from the robot 102 but still be able to operate the end effector 112 and the display 110. The surgical assistant 126 may also be positioned across from the surgeon 120 to have access to both the end effector 112 and the display 110. If desired, the locations of the surgeon 120 and assistant 126 may be reversed. The traditional domains of the anesthesiologist 122 and nurse or surgical technician 124 are agnostic to the location of the robot 102 and camera 200.

[0012] With respect to other components of the robot 102, the display 110 may be mounted on the surgical robot 102, or in other exemplary embodiments, the display 110 may be detached from the surgical robot 102, either in the operating room with the surgical robot 102 or at a remote location. The end effector 112 may be coupled to the robotic arm 104 and controlled by at least one motor. In an exemplary embodiment, the end effector 112 may include a guide tube 114 that may receive and orient a surgical instrument 608 (described further herein) used to perform a procedure on the patient 210. As used herein, the term "end effector" is used interchangeably with the terms "end effector" and "effector element." Although generally shown with a guide tube 114, it will be understood that the end effector 112 may be replaced with any suitable instrumentation suitable for use in a procedure. In some embodiments, the end effector 112 may include any known structure for effecting movement of the surgical instrument 608 in a desired manner.

[0013] The surgical robot 102 is capable of controlling the translation and orientation of the end effector 112. The robot 102 is capable of moving the end effector 112 along, for example, the x, y, and z axes. The end effector 112 may be configured to selectively rotate about one or more of the x, y, and z axes, as well as the Z frame axis (such that one or more of the Euler angles (e.g., roll, pitch, and / or yaw) associated with the end effector 112 may be selectively controlled). In some exemplary embodiments, selective control of the translation and orientation of the end effector 112 may enable the performance of medical procedures with significantly improved precision, as compared to, for example, conventional robots that utilize six degree-of-freedom robotic arms that include only rotational axes. For example, the surgical robot system 100 may be used to operate on a patient 210, where the robot arm 104 may be positioned over the body of the patient 210, and the end effector 112 is selectively angled relative to the z axis toward the body of the patient 210.

[0014] In some exemplary embodiments, the position of the surgical instrument 608 may be dynamically updated such that the surgical robot 102 is aware of the location of the surgical instrument 608 at all times during the procedure. As a result, in some exemplary embodiments, the surgical robot 102 may rapidly move the surgical instrument 608 to a desired position without further assistance from the physician (unless the physician so desires). In some further embodiments, the surgical robot 102 may be configured to correct the path of the surgical instrument 608 if it deviates from a selected pre-planned trajectory. In some exemplary embodiments, the surgical robot 102 may be configured to allow stopping, modifying, and / or manual control of the movement of the end effector 112 and / or the surgical instrument 608. Thus, during use, in exemplary embodiments, a physician or other user may operate the system 100 and have the option to stop, modify, or manually control the autonomous movement of the end effector 112 and / or the surgical instrument 608. Further details of the surgical robotic system 100, including the control and movement of the surgical instrument 608 by the surgical robot 102, can be found in co-pending U.S. patent application Ser. No. 13 / 924,505, which is incorporated herein by reference in its entirety.

[0015] The robotic surgical system 100 may include one or more tracking markers 118 configured to track the movement of the robot arm 104, the end effector 112, the patient 210, and / or the surgical instrument 608 in three dimensions. In an exemplary embodiment, the tracking markers 118 may be mounted (or otherwise secured) on an outer surface of the robot 102, such as, for example, without limitation, on the base 106, the robot arm 104, or the end effector 112 of the robot 102. In an exemplary embodiment, at least one tracking marker 118 of the tracking markers 118 may be mounted or otherwise secured to the end effector 112. One or more tracking markers 118 may further be mounted (or otherwise secured) to the patient 210. In an exemplary embodiment, the tracking markers 118 may be positioned on the patient 210 away from the surgical field 208 to reduce the possibility of being obscured by the surgeon, surgical tools, or other parts of the robot 102. Additionally, one or more tracking markers 118 may be further attached (or otherwise secured) to a surgical tool 608 (e.g., a screwdriver, a dilator, an implant inserter, etc.). In this manner, the tracking markers 118 allow each of the marked objects (e.g., the end effector 112, the patient 210, and the surgical tool 608) to be tracked by the robot 102. In an exemplary embodiment, the system 100 may use the tracking information collected from each of the marked objects to calculate, for example, the orientation and location of the relative positions of the end effector 112, the surgical instrument 608 (e.g., positioned within the tube 114 of the end effector 112), and the patient 210.

[0016] In an exemplary embodiment, one or more of the markers 118 may be optical markers. In some embodiments, the positioning of one or more tracking markers 118 on the end effector 112 may maximize the accuracy of the position measurement by serving to check or verify the position of the end effector 112. Further details of the surgical robotic system 100, including the control, movement, and tracking of the surgical robot 102 and surgical instruments 608, can be found in co-pending U.S. patent application Ser. No. 13 / 924,505, which is incorporated herein by reference in its entirety.

[0017] Exemplary embodiments include one or more markers 118 coupled to the surgical instrument 608. In exemplary embodiments, for example, these markers 118 coupled to the patient 210 and the surgical instrument 608, as well as the markers 118 coupled to the end effector 112 of the robot 102, may include conventional infrared light emitting diodes (LEDs) or Optotrak® diodes that can be tracked using a commercially available infrared optical tracking system such as Optotrak®. Optotrak® is a registered trademark of Northern Digital Inc., Waterloo, Ontario, Canada. In other embodiments, the markers 118 may include conventional reflective spheres that can be tracked using a commercially available optical tracking system such as Polaris Spectra. Polaris Spectra is also a registered trademark of Northern Digital, Inc. In one exemplary embodiment, the markers 118 coupled to the end effector 112 are active markers including infrared light emitting diodes that can be turned on and off, and the markers 118 coupled to the patient 210 and surgical instrument 608 include passive reflective spheres.

[0018] In an exemplary embodiment, light emitted from and / or reflected by marker 118 may be detected by camera 200 and used to monitor the location and movement of the marked object. In alternative embodiments, marker 118 may include a radio frequency and / or electromagnetic reflector or transceiver, and camera 200 may include or be replaced by a radio frequency and / or electromagnetic transceiver.

[0019] Similar to the surgical robotic system 100, FIG. 3 illustrates a surgical robotic system 300 and a camera stand 302 in a docked configuration consistent with an exemplary embodiment of the present disclosure. The surgical robotic system 300 may include a robot 301 including a display 304, an upper arm 306, a lower arm 308, an end effector 310, a vertical column 312, casters 314, a cabinet 316, a tablet drawer 318, a connector panel 320, a control panel 322, and an information ring 324. The camera stand 302 may include a camera 326. These components are described in more detail with respect to FIG. 5. FIG. 3 illustrates the surgical robotic system 300 in a docked configuration, where the camera stand 302 nests with the robot 301, for example, when not in use. Those skilled in the art will appreciate that the camera 326 and the robot 301 may be separated from one another and positioned in any suitable location during a surgical procedure, for example, as shown in FIGS. 1 and 2. 4 illustrates a base 400 consistent with an exemplary embodiment of the present disclosure. The base 400 may be a portion of the surgical robotic system 300 and may include a cabinet 316. The cabinet 316 may house certain components of the surgical robotic system 300, including, but not limited to, a battery 402, a power distribution module 404, a platform interface board module 406, a computer 408, a handle 412, and a tablet drawer 414. The connections and relationships between these components are described in more detail with respect to FIG.

[0020] 5 illustrates a block diagram of certain components of an exemplary embodiment of the surgical robotic system 300. The surgical robotic system 300 may include a platform subsystem 502, a computer subsystem 504, a motion control subsystem 506, and a tracking subsystem 532. The platform subsystem 502 may further include a battery 402, a power distribution module 404, a platform interface board module 406, and a tablet charging station 534. The computer subsystem 504 may further include a computer 408, a display 304, and a speaker 536. The motion control subsystem 506 may further include a driver circuit 508, motors 510, 512, 514, 516, 518, stabilizers 520, 522, 524, 526, an end effector 310, and a controller 538. The tracking subsystem 532 may further include a position sensor 540 and a camera converter 542. The system 300 may also include a foot pedal 544 and a tablet 546 .

[0021] Input power is provided to the system 300 via a power supply 548, which may be provided to a power distribution module 404. The power distribution module 404 is configured to receive the input power and generate different power supply voltages that are provided to other modules, components, and subsystems of the system 300. The power distribution module 404 may be configured to provide different voltage supplies to the platform interface module 406, which may be provided to other components such as the computer 408, the display 304, the speaker 536, the driver 508, and may power, for example, the motors 512, 514, 516, 518 and the end effector 310, the motor 510, the ring 324, the camera converter 542, and other components of the system 300, such as fans for cooling electrical components within the cabinet 316.

[0022] The power distribution module 404 may also provide power to other components, such as a tablet charging station 534, which may be located in the tablet drawer 318. The tablet charging station 534 may be in wireless or wired communication with a tablet 546 to charge the table 546. The tablet 546 may be used by a surgeon as described herein, consistent with this disclosure. The power distribution module 404 may also be connected to a battery 402, which serves as a temporary power source when the power distribution module 404 does not receive power from the input power 548. At other times, the power distribution module 404 may serve to charge the battery 402 as needed.

[0023] Other components of the platform subsystem 502 may also include a connector panel 320, a control panel 322, and a ring 324. The connector panel 320 may serve to connect different devices and components to the system 300 and / or associated components and modules. The connector panel 320 may include one or more ports that accept lines or connections from different components. For example, the connector panel 320 may have a ground terminal port that may ground the system 300 to other equipment, a port for connecting a foot pedal 544 to the system 300, and a port for connecting to a tracking subsystem 532 that may include a position sensor 540, a camera converter 542, and a camera 326 associated with the camera stand 302. The connector panel 320 may also include other ports to enable USB, Ethernet, HDMI communication to other components such as the computer 408. The control panel 322 may provide various buttons or indicators that control the operation of the system 300 and / or provide information about the system 300. For example, the control panel 322 may include buttons for turning the power of the system 300 on or off, for raising and lowering the vertical column 312, and for raising and lowering the stabilizers 520-526, which may be designed to engage the casters 314 and lock the system 300 from physically moving. Other buttons may remove all motor power and apply a mechanical brake to stop all motion from occurring, which may shut down the system 300 in an emergency. The control panel 322 may also have indicators that notify the user of certain system conditions, such as a line power indicator or charge status of the battery 402.

[0024] The rings 324 may be visual indicators to inform a user of the system 300 of the various modes in which the system 300 is operating and of specific warnings to the user.

[0025] The computer subsystem 504 includes the computer 408, the display 304, and a speaker 536. The computer 504 includes an operating system and software for operating the system 300. The computer 504 may receive and process information from other components (e.g., the tracking subsystem 532, the platform subsystem 502, and / or the motion control subsystem 506) in order to display the information to a user. Additionally, the computer subsystem 504 may also include a speaker 536 to provide audio to a user.

[0026] The tracking subsystem 532 may include a position sensor 504 and a converter 542. The tracking subsystem 532 may correspond to a camera stand 302 including a camera 326 as described with respect to FIG. 3. The position sensor 504 may be the camera 326. The tracking subsystem may track the location of specific markers located on different components of the system 300 and / or on the instruments used by the user during the surgical procedure. This tracking may be done in a manner consistent with the present disclosure, including the use of infrared technology to track the location of active or passive elements, such as LEDs or reflective markers, respectively. The location, orientation, and position of structures having these types of markers may be provided to the computer 408 and shown to the user on the display 304. For example, a surgical instrument 608 having these types of markers and tracked in this manner (which may be referred to as a navigation space) may be shown to the user in relation to a three-dimensional image of the patient's anatomy. The motion control subsystem 506 may be configured to physically move the vertical column 312, the upper arm 306, the lower arm 308, or rotate the end effector 310. The physical movement may be accomplished through the use of one or more motors 510-518. For example, the motor 510 may be configured to vertically raise and lower the vertical column 312. The motor 512 may be configured to laterally move the upper arm 308 about a point of engagement with the vertical column 312, as shown in FIG. 3. The motor 514 may be configured to laterally move the lower arm 308 about a point of engagement with the upper arm 308, as shown in FIG. 3. The motors 516 and 518 may be configured to move the end effector 310 in such a way that one may control the roll and one may control the tilt, thereby providing multiple angles through which the end effector 310 may be moved. These movements may be accomplished by a controller 538 that is disposed on the end effector 310 and controls these movements via load cells that are activated by the user and that may engage these load cells to cause the system 300 to move in a desired manner.

[0027] Additionally, the system 300 may provide for automated movement of the vertical column 312, upper arm 306, and lower arm 308 through a user indicating on the display 304 (which may be a touch screen input device) the location of a surgical instrument or component on a three-dimensional image of the patient's anatomy on the display 304. The user may initiate this automated movement by stepping on a foot pedal 544 or by some other input means.

[0028] 6 illustrates a surgical robotic system 600 according to one exemplary embodiment. The surgical robotic system 600 may include an end effector 602, a robotic arm 604, a guide tube 606, an instrument 608, and a robot base 610. The instrument tool 608 may be mounted to a tracking array 612 including one or more tracking markers (such as marker 118) and may have an associated trajectory 614. The trajectory 614 may represent a path of movement that the instrument tool 608 is configured to follow once positioned through or secured within the guide tube 606, such as an insertion path of the instrument tool 608 into a patient. In an exemplary procedure, the robotic base 610 may be configured to be in electronic communication with the robotic arm 604 and the end effector 602 such that the surgical robotic system 600 may assist a user (e.g., a surgeon) in operating on the patient 210. The surgical robotic system 600 may be consistent with the surgical robotic systems 100 and 300 described above.

[0029] The tracking array 612 may be mounted on the instrument 608 to monitor the location and orientation of the instrument tool 608. The tracking array 612 may be attached to the instrument 608 and may include a tracking marker 804. As best seen in FIG. 8, the tracking marker 804 may be, for example, a light emitting diode and / or other type of reflective marker (e.g., marker 118 as described elsewhere herein). The tracking device may be one or more line of sight devices associated with the surgical robotic system. As an example, the tracking device may be one or more cameras 200, 326 associated with the surgical robotic system 100, 300 and may track the tracking array 612 for a defined range or relative orientation of the instrument 608 with respect to the robot arm 604, robot base 610, end effector 602, and / or patient 210. The tracking device may be consistent with the structure described in connection with the camera stand 302 and tracking subsystem 532.

[0030] 7A, 7B, and 7C show top, front, and side views, respectively, of an end effector 602 consistent with one exemplary embodiment. The end effector 602 may include one or more tracking markers 702. The tracking markers 702 may be light emitting diodes or other types of active and passive markers, such as the tracking markers 118 described above. In one exemplary embodiment, the tracking markers 702 are infrared emitting active markers that are activated by an electrical signal (e.g., an infrared light emitting diode (LED)). Thus, the tracking markers 702 may be activated such that the infrared markers 702 are visible to the cameras 200, 326, or may be deactivated such that the infrared markers 702 are invisible to the cameras 200, 326. Thus, when the marker 702 is active, the end effector 602 may be controlled by the system 100, 300, 600, and when the marker 702 is deactivated, the end effector 602 may be locked in position and may not be able to be moved by the system 100, 300, 600.

[0031] The markers 702 may be disposed on or within the end effector 602 such that the markers 702 are visible to one or more cameras 200, 326 or other tracking devices associated with the surgical robotic system 100, 300, 600. The cameras 200, 326 or other tracking devices may track the end effector 602 by following the movement of the tracking markers 702 as the end effector 602 moves to different positions and viewing angles. The location of the markers 702 and / or the end effector 602 may be displayed on a display 110, 304 associated with the surgical robotic system 100, 300, 600, such as the display 110 shown in FIG. 2 and / or the display 304 shown in FIG. 3. This display 110, 304 may allow a user to ensure that the end effector 602 is in a desired position relative to the robotic arm 604, the robotic base 610, the patient 210, and / or the user.

[0032] 7A, the markers 702 may be positioned around the surface of the end effector 602 such that a tracking device positioned away from the surgical field 208 and facing the robot 102, 301 and camera 200, 326 can view at least three of the markers 702 throughout a range of common orientations of the end effector 602 relative to the tracking device 100, 300, 600. For example, distributing the markers 702 in this manner allows the end effector 602 to be monitored by the tracking device as it is translated and rotated within the surgical field 208.

[0033] Additionally, in an exemplary embodiment, the end effector 602 may be equipped with an infrared (IR) receiver that may detect when the external camera 200, 326 is ready to read the marker 702. Upon this detection, the end effector 602 may then illuminate the marker 702. When the IR receiver detects that the external camera 200, 326 is ready to read the marker 702, it may signal that the duty cycle of the marker 702, which may be a light emitting diode, needs to be synchronized to the external camera 200, 326. This may also allow for lower power consumption for the robotic system as a whole, where the marker 702 will only be illuminated at the appropriate time, instead of being illuminated continuously. Furthermore, in an exemplary embodiment, the marker 702 may be powered off to prevent interference with other navigation tools, such as different types of surgical instruments 608.

[0034] 8 illustrates one type of surgical instrument 608 including a tracking array 612 and a tracking marker 804. The tracking marker 804 can be of any type described herein, including, but not limited to, a light emitting diode or a reflective ball. The marker 804 is monitored by a tracking device associated with the surgical robotic system 100, 300, 600, which can be one or more of the gaze cameras 200, 326. The cameras 200, 326 can track the location of the instrument 608 based on the position and orientation of the tracking array 612 and the marker 804. A user, such as a surgeon 120, can orient the instrument 608 such that the tracking array 612 and the marker 804 are sufficiently recognized by the tracking device or camera 200, 326 to display the instrument 608 and the marker 804 on the display 110 of the exemplary surgical robotic system, for example.

[0035] The manner in which the surgeon 120 may place an instrument 608 within the guide tube 606 of the end effector 602 and adjust the instrument 608 is apparent in FIG. 8. The hollow tube or guide tube 114, 606 of the end effector 112, 310, 602 is sized and configured to receive at least a portion of the surgical instrument 608. The guide tube 114, 606 is configured to be oriented by the robotic arm 104 such that the insertion and trajectory of the surgical instrument 608 can reach a desired anatomical target in or on the body of the patient 210. The surgical instrument 608 may include at least a portion of a generally cylindrical instrument. Although a screwdriver is illustrated as the surgical tool 608, it will be understood that any suitable surgical tool 608 may be positioned by the end effector 602. By way of example, the surgical instruments 608 may include one or more of a guidewire, a cannula, a retractor, a drill, a reamer, a screwdriver, an insertion tool, a removal tool, etc. Although the hollow tubes 114, 606 are shown as having a generally cylindrical configuration, it will be understood by those skilled in the art that the guide tubes 114, 606 may have any suitable shape, size, and configuration desired for accommodating the surgical instruments 608 and accessing the surgical site.

[0036] 9A-9C show a portion of an end effector 602 and a robotic arm 604 consistent with one exemplary embodiment. The end effector 602 may further include a body 1202 and a clamp 1204. The clamp 1204 may include a handle 1206, a ball 1208, a spring 1210, and a lip 1212. The robotic arm 604 may further include a recess 1214, a mounting plate 1216, a lip 1218, and a magnet 1220. The end effector 602 may mechanically interfere and / or engage with the surgical robotic system and the robotic arm 604 via one or more couplings. For example, the end effector 602 may engage with the robotic arm 604 via a locating coupling and / or a reinforcing coupling. These couplings may fasten the end effector 602 to the robotic arm 604 outside of a flexible sterile barrier. In one exemplary embodiment, the positioning coupling can be a magneto-kinematic mount and the reinforcing coupling can be a five-bar over-center clamp linkage.

[0037] With respect to the positioning coupling, the robot arm 604 may include a mounting plate 1216, which may be of a non-magnetic material, one or more recesses 1214, a lip 1218, and a magnet 1220. The magnet 1220 is mounted under each of the recesses 1214. A portion of the clamp 1204 may include a magnetic material and be attracted by the one or more magnets 1220. The magnetic attraction of the clamp 1204 and the robot arm 604 causes the ball 1208 to seat in the respective recess 1214. For example, the ball 1208 as shown in FIG. 9B will seat in the recess 1214 as shown in FIG. 9A. This seating may be considered a magnetically assisted kinematic coupling. The magnet 1220 may be configured to have sufficient strength to support the full weight of the end effector 602 regardless of the orientation of the end effector 602. The positioning coupling may be any type of kinematic mount that uniquely constrains six degrees of freedom.

[0038] For a reinforced connection, a portion of the clamp 1204 may be configured to be a fixed ground link, and thus the clamp 1204 may serve as a five-bar linkage. When the lips 1212 and 1218 engage the clamp 1204 to secure the end effector 602 and the robot arm 604, the end effector 602 may be fastened to the robot arm 604 by closing the clamp handle 1206. When the clamp handle 1206 is closed, the spring 1210 may be stretched or stressed while the clamp 1204 is in the locked position. The locked position may be a position that provides an over-center linkage. Because the closed position is over-center, the linkage will not open unless a force is applied to the clamp handle 1206 to release the clamp 1204. Thus, in the locked position, the end effector 602 may be rigidly secured to the robot arm 604.

[0039] The spring 1210 may be a curved beam under tension. The spring 1210 may be constructed from a material that exhibits high stiffness and high yield strain, such as virgin PEEK (Polyetheretherketone). The linkage between the end effector 602 and the robotic arm 604 may provide a sterile barrier between the end effector 602 and the robotic arm 604 without interfering with the fastening of the two connections.

[0040] The stiffening coupling may be a linkage with multiple spring members. The stiffening coupling may latch with a cam or friction based mechanism. The stiffening coupling may also be a sufficiently strong electromagnet that supports fastening the end effector 102 to the robot arm 604. The stiffening coupling may be a multi-piece collar that is completely separate from either the end effector 602 and / or the robot arm 604, that slides over the interface between the end effector 602 and the robot arm 604, and tightens with a screw mechanism, over-center linkage, or cam mechanism.

[0041] 10 and 11, before or during a surgical procedure, a specific registration procedure may be performed to track the object and the target anatomical structures of the patient 210 in both navigation space and image space. To perform such registration, a registration system 1400 as shown in FIG.

[0042] To track the position of the patient 210, the patient tracking device 116 may include a patient immobilization fixture 1402 that is fixed to a rigid anatomical structure of the patient 210, and a dynamic reference base (DRB) 1404 may be securely attached to the patient immobilization fixture 1402. For example, the patient immobilization fixture 1402 may be inserted into an opening 1406 in the dynamic reference base 1404. The dynamic reference base 1404 may include markers 1408 that are visible to a tracking device, such as the tracking subsystem 532. These markers 1408 may be optical markers or reflective spheres, such as the tracking markers 118, as described previously herein.

[0043] The patient immobilization device 1402 may be attached to a rigid anatomical structure of the patient 210 and remain attached throughout the surgical procedure. In an exemplary embodiment, the patient immobilization device 1402 is attached to a rigid area of ​​the patient 210, such as a bone located away from the target anatomical structure undergoing the surgical procedure. To track the target anatomical structure, the dynamic reference base 1404 is associated with the target anatomical structure by using an alignment fixture that is temporarily placed on or near the target anatomical structure to align the dynamic reference base 1404 to the location of the target anatomical structure.

[0044] The alignment fixture 1410 is attached to the patient immobilization fixture 1402 by using a pivot arm 1412. The pivot arm 1412 is attached to the patient immobilization fixture 1402 by inserting the patient immobilization fixture 1402 through an opening 1414 in the alignment fixture 1410. The pivot arm 1412 is attached to the alignment fixture 1410 by, for example, inserting a knob 1416 through an opening 1418 in the pivot arm 1412.

[0045] The registration fixture 1410 may be positioned over the target anatomical structure using the pivoting arm 1412, and its location may be determined in image space and navigation space using tracking markers 1420 and / or fiducials 1422 on the registration fixture 1410. The registration fixture 1410 may include a collection of markers 1420 that are visible in navigation space (e.g., the markers 1420 may be detectable by the tracking subsystem 532). The tracking markers 1420 may be optical markers visible in infrared light, as previously described herein. The registration fixture 1410 may also include a collection of fiducials 1422, such as, for example, bearing balls, that are visible in imaging space (e.g., a three-dimensional CT image). As described in more detail with respect to FIG. 11, the target anatomical structure may be associated with the dynamic fiducial base 1404 using the registration fixture 1410, thereby allowing a representation of the object in navigation space to be superimposed on an image of the anatomical structure. The dynamic reference base 1404, placed at a location away from the target anatomical structure, can provide a reference point, thereby allowing the alignment fixture 1410 and / or pivot arm 1412 to be removed from the surgical area.

[0046] 11 illustrates an exemplary method 1500 for registration consistent with this disclosure. Method 1500 begins at step 1502, where a graphical representation (or image(s)) of the target anatomical structure may be imported into system 100, 300, 600, e.g., computer 408. The graphical representation may be a three-dimensional CT or fluoroscopy scan of the target anatomical structure of patient 210, including detectable imaging patterns of registration fixture 1410 and fiducials 1420.

[0047] In step 1504, the imaging pattern of the fiducials 1420 is detected, registered in imaging space, and stored in computer 408. Optionally, at this point, in step 1506, a graphical representation of the registration fixture 1410 may be superimposed on the image of the target anatomy.

[0048] In step 1508, the navigation pattern of the alignment fixture 1410 is detected and aligned by recognizing the marker 1420. The marker 1420 may be an optical marker recognized in the navigation space through infrared light by the tracking subsystem 532 via the position sensor 540. Thus, the location, orientation, and other information of the target anatomical structure is aligned in the navigation space. Thus, the alignment fixture 1410 may be recognized in both the image space through the use of the fiducials 1422 and the navigation space through the use of the markers 1420. In step 1510, the alignment of the alignment fixture 1410 in the image space is transferred to the navigation space. This transfer is performed, for example, by using the relative position of the imaging pattern of the fiducials 1422 compared to the position of the navigation pattern of the markers 1420.

[0049] In step 1512, the registration of the navigation space of the registration fixture 1410 (registered with the image space) is further transferred to the navigation space of the dynamic registration array 1404 mounted on the patient immobilization device 1402. Thus, since the navigation space is associated with the image space, the registration fixture 1410 may be removed and the dynamic reference base 1404 may be used to track the target anatomical structure in both the navigation space and the image space.

[0050] In steps 1514 and 1516, the navigation space may be overlaid on the image space and an object having a marker visible in the navigation space (e.g., the surgical instrument 608 having the optical marker 804). The object may be tracked through a graphical representation of the surgical instrument 608 on the image of the target anatomy.

[0051] 12A-12B illustrate an imaging device 1304 that may be used in conjunction with the robotic system 100, 300, 600 to obtain pre-operative, intra-operative, post-operative, and / or real-time image data of the patient 210. Any suitable object may be imaged using the imaging system 1304 for any suitable procedure. The imaging system 1304 may be any imaging device, such as an imaging device 1306 and / or a C-arm 1308 device. It may be desirable to take X-rays of the patient 210 from a number of different positions without requiring frequent manual repositioning of the patient 210 that may be required in an X-ray system. As shown in FIG. 12A, the imaging system 1304 may be in the form of a C-arm 1308 that includes an elongated C-shaped member that terminates in opposing distal ends 1312 of a "C" shape. The C-shaped member 1130 may further include an X-ray source 1314 and an image receptor 1316. The space within the arm's C-arm 1308 may provide room for the physician to access the patient substantially without interference from the X-ray support structure 1318. As shown in FIG. 12B, the imaging system may include an imaging device 1306 having a gantry housing 1324 mounted to a support structure imaging device support structure 1328, such as a wheeled mobile cart 1330 with wheels 1332, which may enclose an image capture portion, not shown. The image capture portion may include an X-ray source and / or light emitting portion and an X-ray receiving portion and / or image receiving portion, which may be disposed at approximately 180 degrees from each other and mounted on a rotor (not shown) relative to the orbit of the image capture portion. The image capture portion may be operable to rotate 360 ​​degrees during image acquisition. The image capture portion may rotate about a center point and / or axis, allowing image data of the patient 210 to be acquired from multiple directions or in multiple planes. Although a particular imaging system 1304 is illustrated herein, it will be understood that any suitable imaging system may be selected by one of ordinary skill in the art.

[0052] There are methods to display a simulated projection of a surgical tool superimposed on a fluoroscopic image to aid surgery through one-way registration of a medical image into a tracking space. For example, a calibration fixture may be mounted on the image intensifier of a fluoroscope, as shown in FIG. 13. The fixture includes a row of small metal balls (hereafter referred to as "BB") with known spacing that appear on the X-ray image, and also includes an optical tracking array that provides the three-dimensional (3D) position of the fixture in the tracking space. Through image processing and geometric calculations, it can be determined how a tool placed in the path of the X-ray appears as a projection on the X-ray image. The 3D position of the tool with the attached tracking array is tracked in the coordinate system of a tracker (e.g., a camera). A graphical representation of the tool is then superimposed on the X-ray image to provide a "virtual fluoroscopy" with approximately the same visual information as would be seen if continuous X-rays were taken while holding the tool in the operative field. The advantage of this method is that the patient and medical staff are exposed to much less radiation, since virtual fluoroscopy can provide continuous updates of tool positions superimposed on a single x-ray image.

[0053] Although this method maps 3D tool positions to a two-dimensional (2D) medical image, the application does not require mapping of points detected on the 2D medical image to the 3D tracking space, i.e., aligning the medical image space with the tracking space. However, it is possible to obtain such a mapping by considering a vector that runs from the emitter to the collector. FIG. 14 shows an X-ray (e.g., fluoroscopic) collector plate 1702 showing theoretical projections of a BB 1710 in two planes 1704 and 1706 at different distances from a source 1708. The X-ray collector plate 1702, plane 1 1706, and plane 2 1704 are shown to be parallel and concentric. In this example, the X-ray emitter 1708 is assumed to be a point, and the rays from the source to the collector exit from this point in a cone-shaped pattern. Due to this conical pattern, BBs 1710 on Plane 1 1706 appear magnified on the x-ray collector plate 1702 relative to BBs 1710 on Plane 2 1704, even though in this example they are actually spaced the same. This phenomenon is known as parallax.

[0054] Consider the case where one x-ray is taken from a substantially different viewpoint than another, as shown in FIG. 15, and the exact location of the collector and emitter in 3D is known from tracking or other means, vectors running in a cone pattern from the emitter to the collector can be traced back to where they intersect with an anatomical interest point 1802 present in both x-rays. In this case, "vector" can mean a vector determined from the visible x-ray shadow of the BB, or any vector calculated (e.g., interpolated) to match the cone pattern estimated from the visible x-ray shadow. The 3D location of that anatomical interest point can then be determined, since there is a unique solution at the intersection of the vectors from the two x-rays. That is, it is not possible to estimate the 3D location of a fiducial from one x-ray, since the fiducial could be anywhere along the vector from the source to the emitter and would appear at the same location on the collector plate. The second x-ray provides a unique location along the vector where the fiducial should be.

[0055] Fig. 14 shows just four BBs 1710 on two parallel planes 1704 and 1706. These BBs may provide the basis of a method for detecting the position of an object in 3D from multiple 2D X-ray views. However, to provide better accuracy, a dense grid of BBs (e.g., tens or hundreds) as shown in Fig. 16 may be used instead, which allows vectors to be interpolated more precisely. The use of more BBs allows for more accurate interpolation and ultimately better 3D accuracy, but the X-ray shadows from more BBs also prevent the surgeon from visualizing the anatomical structures of interest on the X-ray image.

[0056] The implicit assumption is that the positions of the collector plate and emitter source in 3D are known during both shots. For example, the collector plate may have a tracking array attached, and therefore its 3D position is tracked directly. It may also be possible to place the tracker on the emitter. However, doing so has the main drawback that the tracking area needs to be very large to observe both trackers, and the distance between the collector and the emitter may typically be on the order of one meter. Tracking systems such as optical trackers may only have a tracking area of ​​less than one cubic meter. In addition, the emitter may be located outside the field of view for some clinically typical x-ray shots. The emitter source position may instead be calibrated to the collector array, but the extrapolation accuracy in defining the emitter location may be lower with large distances between the collector and emitter, and different amounts of sag when the fluoroscope is oriented differently. Alternatively, the distance and orientation of the emitter source relative to the collector may be determined by a known spacing d, as shown in Figs. 14 and 17. ab 17 can be calculated from two parallel fluoroscopic images of the BB with 1712. The equation provided in Equation 1 holds based on the geometry 2000 shown in FIG.

[0057]

number

[0058] During the ceremony, ●d ec is the distance from the emitter to the collector in mm.

[0059] ●k is the scaling factor to convert pixel coordinates on the fluoroscopy output to mm.

[0060] ●l a is the lateral distance in mm in plane A between BB1a and BB2a.

[0061] ●l b is the lateral distance in mm in plane B between BB1b and BB2b.

[0062] ●y 1a is the lateral distance in mm from the central beam to BB1a.

[0063] ●y 1b is the lateral distance from the central beam to BB1b in mm.

[0064] ●y 2a is the lateral distance in mm from the central beam to BB2a.

[0065] ●y 2b is the lateral distance from the central beam to BB2b in mm.

[0066] ●z ea is the distance in mm from the emitter to plane A (BB1a and BB2a).

[0067] ●z eb is the distance in mm from the emitter to plane B (BB1b and BB2b).

[0068] ●d ab is the longitudinal distance between plane A and plane B in mm.

[0069] ●L2a is the distance in pixel coordinates between the shadows of BB in plane A on the collector.

[0070] ●L 2b is the distance in pixel coordinates between the shadows of BB in plane B on the collector.

[0071] d ec By solving for , we obtain the following equation:

[0072]

number

[0073] Therefore, if the spacing between the planes is known and the spacing between the BBs is known, the distance from the emitter to the collector can be determined through image processing of an X-ray image that includes these BBs. Note that FIG. 17 shows that the distance between the shadows of two adjacent BBs in the two planes is measured. In practice, the distance between several pairs of BBs on the X-ray image can be measured and these distances averaged. In addition, while FIG. 17 shows the distance between the BBs on plane A and plane B as being the same, the physical distance between the BBs may be different and l may be used in the equation. a and l b In practice, it may be desirable to offset the BBs rather than having them equally spaced apart to prevent their projections from partially occluding one another.

[0074] This method for defining the position of the emitter relative to the collector utilizes two parallel plates in defining the emitter direction as well as distance. With the alignment fixture attached to the collector, the emitter to collector direction is assumed to be perpendicular to the plane of the collector and the plane containing the BB. If this assumption is not true, the projections of the BB from the near and far field planes will not overlap symmetrically on the x-ray image. For a given amount of angular deviation of the x-ray plane from the BB plane, the amount of offset of the BB shadow from the symmetric projection is proportional to the distance between the BB planes, with larger plane separation appearing as a larger lateral displacement of the projection on the x-ray image. Through geometry, the lateral offset of the BB shadow can be used to precisely determine the actual orientation of the BB plane relative to the collector plane and therefore the position of the emitter in 3D, or it can be used to manually or automatically adjust the orientation of the alignment fixture on the image intensifier until the BB plane and the collector plate are truly coplanar.

[0075] A scaling factor k is present in the above equation, which is necessary for the subsequent 3D to 2D mapping of the 3D coordinates of the generalized point. In general, to map a 3D point with coordinates x, y, z onto a 2D X-ray image where the X and Y axes of the image are aligned with the x and y axes of a Cartesian coordinate system, Equation 3 holds:

[0076]

number

[0077] where X is the coordinate axis of the 2D X-ray image aligned with the Cartesian X-axis, Y is the coordinate axis of the 2D X-ray image aligned with the Cartesian Y-axis, and z is the Cartesian axis perpendicular to the X-ray image.

[0078] If two fluoroscopic shots are taken at different orientations up to 90 degrees apart, such as one common clinical anteroposterior shot and one common clinical lateral shot, then (X1,Y1) may be defined as the x-ray coordinates (x,y,z) of a point as it appears on x-ray image 1 (e.g., anteroposterior image). The Cartesian coordinates of the point in a local coordinate system aligned with that x-ray plane may be defined as (x1,y1,z1). Similarly, (X2,Y2) may be defined as the x-ray coordinates of the same point as it appears on x-ray image 2 (e.g., lateral image). The Cartesian coordinates of the point in a local coordinate system aligned with that x-ray plane may be defined as (x2,y2,z2). Since a tracking system can be used to detect the 3D position of the x-ray collector while the fluoroscope is in each orientation, the transformation T12 from Cartesian coordinate system 1 to Cartesian coordinate system 2 is known, where T12 is a standard 4×4 transformation matrix as commonly used in the field. Therefore, there exists a unique solution to Equation 4.

[0079]

number

[0080] Note that each of the two coordinate systems is oriented such that the z-axis is perpendicular to the respective X-ray plane, the origin of the z-axis is in the respective X-ray plane, and the origins of the x- and y-axes are in the center of the X-ray plane. The directions of x and y relative to the X-ray plane may be arbitrary. The transformation (T) from the first 3D coordinate system to the second 3D coordinate system can be performed by tracking the location of the X-ray plane in 3D, for example using 3D optical tracking. 12 ) can be determined.

[0081] The method for defining the 3D Cartesian coordinate system associated with the two fluoroscopic views may assume that the BBs are uniformly projected onto the image intensifier. However, images obtained from a fluoroscope are generally accompanied by distortions such as pincushion distortion, s-shaped distortion, etc. These types of distortions may be corrected using image processing before applying the methods described herein. The distortion correction may take advantage of the fact that the BBs are arranged in a symmetrical pattern on the registration device. Thus, an X-ray projected through a known symmetrical pattern should produce an image with matching symmetry. The spacing between the BBs and the alignment of the rows of BBs may be determined through image processing and compared to the expected projection of the BBs. Algorithms commonly known in image processing, such as affine transformations, may be used to match the projected X-ray image to the known and expected symmetry. The same corrections may be applied to anatomical images on the X-ray, so that the resulting X-ray image should represent a distortion-free projection and allow for effective calculation of the registration as described herein.

[0082] In an embodiment, the symmetric pattern used to correct the distortion can be a square pattern as shown in Figure 16, a radially symmetric pattern where the BBs are distributed in a polar coordinate system centered on the center of the image, where the BBs share a common radius and azimuth, or any suitable pattern as shown in the fixtures of Figures 18 and 19. As long as the pattern of the actual BBs embedded in the registration fixture is known, the corresponding shadows of the BBs on the X-ray image can be predicted and distortion correction can be applied to make the image match the predicted pattern.

[0083] The process of mapping images from 2D to 3D depends on the correct interpretation of the directions on the X-ray image. For example, if the 2D X-ray image is an anteroposterior image, it is necessary to know whether the 2D image represents a shot with the emitter in front and the collector in rear, or a shot with the emitter in rear and the collector in front. In addition, since fluoroscopic images are generally circular, a means is needed to accurately determine from the BB shadow which direction points left, right, up or down. The plane of the BBs on the fixture may provide information for alignment corrections, such as providing information for rotational orientation of the X-ray image, as well as information on reflections, using the BBs located closest to the X-ray collector. For example, the BB pattern may determine whether the positive z-direction extends from the anterior or posterior side of the viewing plane. In an embodiment, the fixture may include an outer ring of large BBs arranged to uniquely identify aspects of the alignment, such as image rotation and flip. A pattern of BBs for identifying orientation and / or flip may be selected based on the pattern's ability to provide a unique combination of image rotation and flip, as well as the ability of the pattern to provide redundant BBs to increase the reliability of detection. Redundant BBs may be important because not all BBs are visible on any given x-ray shot due to obstruction of BB shadows from tools or implants, or insufficient x-ray penetration through parts of the image.

[0084] In an embodiment, as shown in FIG. 19, links of BBs spaced at various intervals around the perimeter of a standard circular fluoroscopic image may be used, with the shadows of the BBs on the perimeter forming a bit code (e.g., a 32-bit code). In an embodiment, a first plane 2202 with a first array of points and a second plane 2204 with a second array of points may be projected to form a composite image 2206. The code length should be selected to allow the BBs to be spaced far enough apart that there is a small chance that an error in detecting the location of the BBs will cause the BB location to erroneously fall into the location of an adjacent bit, while still providing enough information that is not affected by missing bits. If only a subset of existing BBs is detected and some of the shadows of the BBs are not detected, a comparison of the subset to a known template may provide the correct image orientation and flip regardless of which BBs are missing. If a subset with a large number of missing BBs is detected, an algorithm may determine the correct image orientation and flip. In an embodiment, to know the limits of the algorithm, the system may require that a certain minimum number of BBs be detected before allowing the algorithm to proceed.

[0085] In an embodiment, the orientation matching may utilize a point matching algorithm (e.g., the Kabsch point matching algorithm) or other suitable point matching algorithm that assumes both point sets are scaled the same. The algorithm may then determine a transformation between two point sets, one obtained from the detection of the orientation BB and the other obtained from the fixture 3D model. The fixture orientation markers may then be projected into image space. Since both point sets need to be scaled the same, the algorithm tests a range of projection scalings to find the best match. Once the best match is found, the transformation is scaled appropriately and the algorithm assigns point correspondences between the detected image markers and the physical fixture markers. The resulting transformation may then be applied to the image to rotate and / or flip the image to generate an alignment with the fixture.

[0086] Ring Alignment Fixture: As an alternative to an array of BBs to establish orientation, rings or other shapes, such as those formed from radiopaque materials such as metal wires, can be used as references in the alignment fixture. Referring to FIG. 20, a ring alignment fixture 2300 is shown with two parallel rings 2304 and 2306 of the same or different diameters (e.g., 50-300 mm) that are concentrically positioned in parallel planes spaced apart (e.g., 50-300 mm apart). To facilitate identification of the centers of the rings 2304 and 2306, the rings may also have one or more crosshairs 2308A and 2308B formed from wire or other radiopaque material of the same or different diameter as the rings themselves. Some desirable features of the rings include rings that are precisely circular, rings where the crosshairs pass through the exact center so that the diameter of the projected ellipse and crosshair intersections are precise, etc. Additionally, it may be desirable for the cross-section of the ring to be circular rather than flat, so that the rings will project properly when they are at an angle to the x-ray image. Possible methods for shaping the ring include welding or otherwise adhering sections of wire together, rapid prototyping (3D printing) using radiopaque build materials, or etching using methods similar to those used to fabricate printed circuit boards.

[0087] When an x-ray image is taken of the ring alignment fixture 2300 centered on the collector plate, the x-ray image should appear as two concentric circles 2402 and 2404, as shown in Figure 21. If an x-ray image is taken while the ring alignment fixture 2300 is not parallel or centered relative to the collector plate, the x-ray image will appear as two ellipses 2502 and 2504, as shown in Figure 22.

[0088] Additionally, tracking markers 2302A-D may be used as a reference for positioning the rings of ring alignment fixture 2300 in 3D, such as by utilizing an array of optical markers, magnetic sensors, or other similar 3D tracking methods. For reference, it may be convenient to define a local coordinate system on alignment fixture 2300. For example, the reference local coordinate system may have its origin at the center of the ring closer to the x-ray emitter, a second (e.g., parallel) ring closer to the collector, and the x- and y-axes may coincide with crosshairs identifying the center of the first ring, and the z-axis coincides with a vector connecting the centers of the two rings.

[0089] In an embodiment, mapping points from 3D to 2D using a ring alignment fixture can utilize vectors passing through known points on both rings that are created to form a conical pattern, which is then used to interpolate vectors through the region of interest.

[0090] In an embodiment, a set of common transformations (i.e., rotation, translation, magnification) may be applied, such as with transformation parameters estimated from features on the image. As an example, consider a 3D coordinate system based on a two-ring fixture, where the coordinate system is centered on a first ring closer to the emitter as the near-field ring, and a second ring closer to the collector as the far-field ring. In this example, the near-field and far-field rings may be of the same diameter, and several transformations may be applied to map points from this coordinate system to the coordinate system of the collector plate.

[0091] A non-limiting set of examples of exemplary transformations are shown in Figs. 23-27. Fig. 23 shows transformation step 1, which rotates by θ about z (e.g., θ is the angle that allows a subsequent rotation α about y to occur). Note that in this figure, the rings are displayed in 3D with no parallax, and the near-field and far-field rings are exactly overlapping at the starting orientation. Fig. 24 shows transformation step 2, which rotates by α about y. Note that the rotation occurs about the center of the near-field ring (e.g., the ring closer to the emitter). Fig. 25 shows transformation step 3, which rotates in a plane to match the viewpoint of the radiograph (e.g., instead of using the y-axis as the rotation axis for the incidence angle α, find the angle from y in the xy plane to arrive at the actual rotation axis). Fig. 26 shows transformation step 4, which displaces by dx,dy from the coordinate system center. Fig. 27 shows transformation step 5, which scales according to parallax. In this example, once step 5 is completed, the xy plane represents the points mapped to the 2D plane. In step 5, the expansion is performed according to Equation 3.

[0092] In this example, the points on the near field ring have larger z values ​​than the points on the far field ring, so the near field ring will appear more magnified than the far field ring in the final image. Additionally, the rotation of the ring in the xy plane may appear different depending on how far the ring is from x,y=0,0.

[0093] Thus, to go from a 3D point specified in the coordinate system mounted on the ring alignment fixture to a 2D point on the x-ray plane, a series of transformations are applied where there are five unknowns, θ, α, φ, dx, and dy. It is possible to use image processing to estimate these five unknowns from the ring itself. Thus, once these five parameters are defined and the alignment is established, any new point specified as x, y, z in the reference coordinate system can be directly mapped to x-ray image coordinates.

[0094] Many of the calculations for determining the five parameters from the images were performed as described for the BB fixture.ec The ratio of d / k is required. This ratio can be similarly determined from an X-ray image taken of the ring while oriented parallel to the collector plate. Figure 28 shows an outline of the major dimensions as viewed in a plane perpendicular to the plane of the collector plate, with the ring parallel to the collector in the field of view and its shadow appearing on the collector plate. Based on Figure 28, d ec The following equation can be written to determine / k:

[0095]

number

[0096] During the ceremony, d ec is the distance from the emitter to the collector in mm.

[0097] k is a scaling factor to convert pixel coordinates on the fluoroscopy output to mm.

[0098] l a is the diameter of ring A.

[0099] l b is the diameter of ring B.

[0100] y 1a is the lateral distance in mm from the central beam to the edge of Ring A.

[0101] y 1b is the lateral distance in mm from the central beam to the edge of ring B.

[0102] y 2a is the lateral distance in mm from the central beam to the opposite edge of Ring A.

[0103] y 2b is the lateral distance in mm from the central beam to the opposite edge of ring B.

[0104] zea is the distance from the emitter to plane A (to ring A) in mm.

[0105] z eb is the distance from the emitter to plane B (to ring B) in mm.

[0106] d ab is the longitudinal distance between plane A and plane B in mm.

[0107] L 2a is the diameter in pixel coordinates of the shadow of ring A on the collector.

[0108] L 2b is the diameter in pixel coordinates of the shadow of ring B on the collector.

[0109] We now describe a non-limiting example in which the five unknowns (θ, α, φ, dx, dy) may be determined.

[0110] Calculation of the angle of incidence α: Consider a cone beam that strikes a plane at any angle to the cone and projects an image onto a collector plate, as viewed from the viewpoint shown in Figure 29, where the view across the ring is at any angle of incidence to the collector plane from a viewpoint looking across the ring plane. The ring plane is on and off the page as shown in the inset, the view is from positive z, and the reformatted x and y axes are oriented as shown in the 3D coordinate system. In this example, the distance d from the apex of the cone (e.g., the x-ray emitter) to the collector at which the image is perceived is ec The subscript "a" is used because the same incidence angle α and diameter l 0b This is because there is a second ring parallel to this ring with the subscript "b". The coordinate system for the plate and the 3D space above it is such that the center of the 2D image is at X p = 0, and the center of the 3D space is also x r Note that the vertices are positioned as being at .

[0111] Based on FIG. 29, the following equation holds:

[0112]

number

[0113] With reference to FIG. 30, we now consider a fixture with two parallel rings of different diameters. The parameter z ea and z eb represents the z-distance from the emitter to the midpoint of each ring (the intersection of the crosshairs). Figure 30 shows a view across a pair of concentric rings at an arbitrary angle of incidence to the collector plane, from a perspective looking across the ring plane, with the ring plane lying on and off the page (see inset). Based on Figure 30, the following equations hold:

[0114]

number

[0115] z ea (and z eb ), consider another view of the ring, looking across its widest part, as shown in Figure 31, which provides a view of the ring at any angle of incidence from a view rotated 90 degrees from the views of Figures 29 and 30. This gives

[0116] For ring a

[0117]

number

[0118] For ring b

[0119]

number

[0120] Substituting into Equation 7, we get

[0121]

number

[0122] During the ceremony, L 2a = maximum diameter of the elliptical projection of ring a in pixel coordinates.

[0123] L 2b = maximum diameter of the elliptical projection of ring b in pixel coordinates.

[0124] d ec = Distance in mm from emitter to collector.

[0125] d ab = Shortest distance in mm from ring a to ring b.

[0126] k = pixel to mm conversion factor.

[0127] l 0a = known actual diameter of ring a in mm.

[0128] l 0b = known actual diameter of ring b in mm.

[0129] Equation 11 indicates that the widest and narrowest projections of the rings are measured, and slight variations can cause discrepancies in α. Instead, it is useful to base the equation on the displacement of the ring centers, which is less susceptible to error. If the lower ring is "scaled up" to match a known ratio of the diameters of the upper and lower rings (e.g., a ratio of 1 if the rings are the same diameter), the scaling is done on the value of each point on the ring in a coordinate system where the ring points are offset from 0, so that it is the same as if the ring were moved vertically upwards (z direction). Figure 32 shows a diagram of a pair of rings at any incidence angle from the same viewpoint as Figure 29. If the far field ring is scaled up to match the magnification of the near field ring, the z ea =z ebThis is equivalent to physically moving it up the z-axis until

[0130] This z position becomes the z position of the major axis of both ellipses. Image processing allows scaling of the image of the far-field ellipse around the image center until the far-field ellipse diameter to the near-field ellipse diameter matches an expected ratio. For example, if the far-field and near-field rings have the same physical diameter, the x-ray projected far-field ellipse will appear smaller than the near-field ellipse. The points on the far-field ellipse can then be scaled so that the new image of the far-field ellipse has the same diameter as the near-field ellipse. In particular, the only point that needs to be scaled may be the center of the far-field ellipse as defined by the intersection of the crosshairs of the far-field rings. If the far-field ellipse is scaled and the near-field ellipse is not scaled, the offset at the center of the ellipse represents a measurement in image coordinates of the opposite side of a triangle with a hypotenuse equal to the distance between the rings. At this z position, the hypotenuse may be determined in image coordinates, which is the distance between the rings multiplied by the ratio of the major axis of the near-field ellipse to the near-field ring diameter (or the ratio of the major axis of the scaled far-field ellipse to the far-field ring diameter, which is the same by the definition of the scaling factor). Using the opposite side and the hypotenuse, α can be determined by the arcsine function.

[0131]

number

[0132] During the ceremony: D cab = The distance in image coordinates between the center of the unscaled near field ellipse and the scaled far field ellipse.

[0133] L 2a = diameter of the near-field ellipse in image coordinates measured in the direction of the rotation axis (approximately equal to the major axis of the projected ellipse).

[0134] l 0a = near field ring diameter in mm.

[0135] d ab = distance in mm between rings.

[0136] Calculating the azimuth angle φ: The azimuth angle φ (the angle required to place the rotation axis of the ring incidence on the y-axis) may appear to be just an angle relative to the major axis of one of the ellipses. For example, FIG. 33 shows the modeled appearance on an x-ray (with parallax) of two circular rings with an incidence angle of α=20° occurring around the y-axis. The major axes of both ellipses appear to be oriented along the y-axis, and therefore an azimuth angle φ=0° is expected. At first glance, the orientation of the major axis of one or both ellipses can be assessed using image processing and used to determine θ. However, it can be seen that when the ring position is offset from the center of the image, the major axis of the ellipses does not precisely reflect the azimuth angle. In the example shown in FIG. 34, which was generated from numerical data, there is a clear mismatch in the orientation of the major axes of the two ellipses. In FIG. 34, the modeled appearance is shown on an x-ray (with parallax) of two parallel circular rings with an incidence angle of α=24.5° occurring around the y-axis. Both rings are offset from the center of the x-ray. The major axes of both ellipses appear to be at a visible angle to the y-axis. In addition, the major axis of the larger ellipse appears to have a different azimuth angle than that of the smaller ellipse. In this case, the azimuth angle is known to be φ=0°, but the image processing does not give this angle correctly.

[0137] A further consideration is that for small angles it may be difficult to precisely assess the exact direction where the diameter is largest, and therefore a method that uses the orientation of the major axis of the ellipse to determine θ may yield less accurate results. In an embodiment, a method that uses the length of the major axis of the ellipse should yield better results.

[0138] In the scaling implementation described with reference to FIG. 32, it can be seen that the magnification is equivalent to moving the entire ring up the z-axis. Thus, if the far-field ring is appropriately scaled, the two elliptical ring images represent the projections at the same z-coordinate of the near-field and far-field rings. If the centers of the near-field and far-field rings are at the same z-coordinate, the vector connecting the centers of the near-field and far-field rings in x and y represents the path of the rotation axis. The actual rotation axis needs to be perpendicular to this path and also in the xy plane. Thus, the rotation axis can be extracted through image processing by first scaling the center of the far-field ring and then tracing the path connecting the centers of the far-field and near-field ring images. In illustration, FIG. 35 shows the modeled appearance on an x-ray (with parallax) of two parallel circular rings with an incidence angle of α=24.5° occurring about the y-axis. Both rings are offset from the center of the x-ray. The far-field ellipse is scaled about the center of the image until the near-field and far-field ellipses are equal in their major axes. The azimuth angle is known to be φ=0° (i.e. rotation about the y-axis, see FIG. 24), which is the correct result after scaling is performed.

[0139] The angle θ is the angle of the near field vertical crosshair relative to Y or the horizontal crosshair relative to X, after taking into account the viewpoint. Thus, by finding the location of the intersection of the crosshair with the ellipse and then applying the inverse incidence angle, the intersection point in the plane is given and the angle θ can be determined from the arctangent of the x, y coordinates of the crosshair intersection point.

[0140] Note that it is important to know which crosshairs are aligned with X or Y, and which direction of the crosshairs points +X or +Y. This information can be determined from additional features on the fixture that appear on the x-ray image, such as the BB or wires that are close to the positive axis of the reference crosshairs, or any other suitable feature.

[0141] The offset position dx,dy is the x,y coordinate offset of the center of the near field ring. This point can be tracked directly based on a tracker on the fixture and the corresponding point seen on the resulting x-ray. This point can serve as an alignment check; that is, if a navigated probe is aimed at the center of the near field ring, an image of the probe should be seen with its tip at the intersection of the crosshairs of the projected ellipse.

[0142] If the alignment fixture is very accurately mounted on the image intensifier, some of the parameters mentioned above will be zero; i.e., the incidence angle α, the rotation axis reference φ, the displacements dx and dy will all be zero, simplifying the alignment process. Thus, similar to the BB fixture, the location of the intersection of the crosshairs and ring on the x-ray can be used as an adjustment tool instead to extract the transformation parameters. That is, as shown in FIG. 21, if the x-ray shows a difference in the intersection of the center and edge of the ring, the fixture can be adjusted manually or automatically on the image intensifier until the x-ray shows centration, at which point the transformation is simplified and the mapping is at its best accuracy.

[0143] When using a ring in the alignment fixture, correction of distortions can be accomplished in a similar manner to that applied to the BB fixture. To make the distortion correction effective, the crosshairs on the ring fixture require additional features with equally spaced markings placed along each crosshair. These markings can be hatch marks, circles, gaps, or any such features that appear on the visible projection on the x-ray image. The pincushion and s-distortions can then be accounted for and corrected by considering both the straightness of the crosshairs and the spacing between the indices on the crosshairs. Figures 36 and 37 show the manifestation of pincushion and s-distortions on an image when using a ring fixture. It is assumed that pincushion distortions are radially symmetric around the center of the image, so that only one crosshair and markings need be viewed to account for and correct for pincushion distortions, assuming the crosshairs run through the center of the image from one edge to the other. If the pincushion distortions are not symmetric at different angles, additional crosshairs may be required to assess the magnitude of the pincushion in different directions.

[0144] FIG. 36 illustrates pincushion distortion that can occur in a fluoroscope, which shows an x-ray taken through a square wire grid as a pincushion distortion image 3602. For clarity, the pincushion pattern is shown more exaggerated than typical. At the bottom of the figure, a crosshair and a ring with equally spaced gaps in the crosshair are shown in an undistorted state 3604 (left) and then with pincushion distortion 3606 (right). Note that the distortion does not affect the ring, but is clearly visible in the spacing of the gaps in the crosshair, with an increased visible spacing from the center to the outer ring. The magnitude of pincushion distortion is measured as the amount of increase in spacing between indices from the center to the edge of the image. Similarly, barrel distortion appears as a decrease in the gaps in the crosshair from the image center to the ring.

[0145] FIG. 37 illustrates s-distortion that can occur in a fluoroscope, causing an x-ray taken through a square wire grid to appear as an s-distorted image 3702. For clarity, the s-pattern is shown more exaggerated than typical. At the bottom of the figure, a ring with crosshairs is shown without distortion 3704 (left) and then with s-distortion 3706 (right). Note that the distortion does not affect the ring, but is clearly visible in the crosshairs, which have taken on an S-shape. The magnitude of the s-distortion is measured from the amount that the two crosshairs take on an s-shape.

[0146] 3D Surgical Planning in 2D: In planning medical procedures, such as in conjunction with a surgical robotic platform, a plan for the placement of a medical object, such as a surgical screw, may be provided in 3D based on 2D images. For example, in such a plan, a line segment drawn to represent the screw on one of the 2D views may be assumed to have a particular dimension in and out of the plane in which the line segment is drawn (e.g., the z dimension). It may also be assumed to have a particular start and end z coordinate in and out of the plane in which the line segment is drawn. For example, if a pedicle screw is planned on an anterior-posterior and a lateral x-ray image, an appropriate assumption for the z coordinate may be that the dimension of the screw on the lateral x-ray represents the maximum length of the screw. That is, the screw does not angle in and out of the plane, and therefore the z coordinates of the leading and tail ends of the screw on the local coordinate system of the lateral image are identical. Equal z coordinates for the leading and tail ends may be assumed to be appropriate values ​​to place the screw in the center of the anterior-posterior image. That is, if the user selects x and y coordinates in the landscape plan view, whatever z coordinate in the landscape image is used will cause the screw image to appear in the center of the screen in the front-to-back image.

[0147] In embodiments, other means may be used for improved initial guesses on the unknown planning plane. For example, anterior-posterior and lateral images may be used for planning, with the top of both images oriented to represent a rostral anatomical direction. If the user knows through software prompts that they are going to place a left screw by dropping it on the lateral image, then the starting location of the screw on the anteroposterior image may be on the left side of the screen, assuming the left screen is the left anatomical direction.

[0148] Once the initial position is indicated by the user in one view and inferred or otherwise specified by the software in the other view, subsequent repositioning of the screw in either view can be mapped to the other view by fulfilling the forward mapping of 3D coordinates to 2D. For example, the user may have defined the x, y, z coordinates of the screw tip in a local Cartesian coordinate system associated with the alignment fixture while taking the lateral x-ray. If the user then selects and drags a representation of the screw tip through software interaction, the user must move the tip in the xy plane of the Cartesian coordinate system, not in its z direction, since the xy plane of the Cartesian coordinate system is parallel to the image plane. The x and y translations in that local coordinate system (z translation=0) can then be updated through user interaction. Since the transformation between the local coordinate systems of the anteroposterior x-ray and the lateral x-ray is known through tracking, the resulting x, y, z coordinates associated with the local coordinate system of the anteroposterior image can also be updated, allowing the mapping of the planned tip of the screw to a new location in the anteroposterior image. Through a series of updates of one image and then the other, the user can move the screw to a 3D position that is known relative to the tracked positions of both of the alignment fixtures, and therefore known to the camera space and the robot. The robot can then move to a position that allows the screw to be accurately placed.

[0149] It should be noted that if the two coordinate systems of the images are perpendicular, one representing an anteroposterior x-ray and one representing a lateral x-ray, moving the planned representation of the tip or caudal end of the screw on the anteroposterior view in a rostral-caudal direction via software dialogue has the effect of moving the representation of the tip or caudal end of the screw rostrally caudally by the same amount in the lateral view. However, moving the tip or caudal end of the screw to the left or right in the anteroposterior view may not affect the planned tip or caudal end position in the lateral image. Conversely, moving the tip or caudal end of the screw anteriorly or posteriorly in the lateral image does not affect the tip or caudal end position of the screw in the anteroposterior image, but moving the tip or caudal end position of the screw rostrally or caudally in the lateral image will change the representation of the tip or caudal end of the screw in the anteroposterior image rostrally caudally by the same amount. If the two x-rays are not taken perpendicularly, moving the planned leading or trailing end of the screw on one view to the left, right, up, or down will cause the representation on the other view to shift by at least some amount.

[0150] Although it has been described that two views, such as one anteroposterior and one lateral x-ray, are used for planning, a 3D to 2D mapping can be made for any x-ray image, so that the plan can be displayed and updated simultaneously on any number of x-ray images, as long as tracking information of the registration fixtures is obtained as the images are taken. For example, four images taken at 45 degree increments can be displayed in the four quadrants of the screen, and the planned screws can be registered on each view. Using software interaction, updating the planned position in one view will cause the image to change in each of the other views.

[0151] Figures 38-46 show a novel alignment fixture 2 that is configured to mount to the flat panel detector 4 side of a medical imaging device rather than the transmitter side. The alignment fixture 2 of Figure 38 is ideally suited for medical imaging devices that utilize digital imaging technology using a digital flat panel detector 4 on a C-arm, including lower radiation dose and higher image quality compared to image intensifier based C-arm systems.

[0152] The alignment fixture 2 includes a base frame 6, first and second side frames 8, 10, and a kinematic mount 12 that is removably attached to the base frame 6. By definition, the kinematic mount constrains all six degrees of freedom of the side frames 8, 10 relative to the base frame 6.

[0153] The base frame 6 is constructed from an aluminum frame of minimal volume and weight, but may be fabricated from any of a number of reasonable cost, low density, high strength and rigidity materials.

[0154] A radiolucent plate 14 is attached to the base frame 6. In the embodiment shown in Figure 39, the plate 16 includes two plates 14, 16 spaced vertically from each other. The orientation plate 14 is positioned closer to the flat panel detector 4 and the alignment plate 16 is positioned above the orientation plate.

[0155] Each plate is fabricated from a radiolucent material (e.g., carbon fiber, Rohacell foam, acrylic, ABS, or similar material) and contains embedded radiopaque markers 17, 19 that are oriented in a unique configuration for imaging and navigation purposes. In the illustrated embodiment, the radiopaque markers 17, 19 are 1 / 8 inch stainless steel balls, but may be constructed from any number of radiopaque materials and a variety of geometric shapes.

[0156] In one embodiment, the plates 14, 16 are mounted on a precision flat surface on the base frame 6, with the separation distance between the two plates being 10mm to 75mm. In another embodiment, the range is 25mm to 50mm, which may minimize obstruction in the surgical work area for the clinical team. Nevertheless, the plate separation distance may be increased or decreased to improve precision.

[0157] The orientation plate 14 and registration plate 16 are aligned with precision dowel pins 20 via hole and slot configurations to achieve optimum inter-plate alignment accuracy. The hole, slot and pin configurations for the two plates are unique to prevent inaccurate installation.

[0158] FIG. 40A shows an orientation plate 16 having a first set of radiopaque markers 17 in a predetermined pattern, and FIG. 40B shows an alignment plate 18 having a second set of radiopaque markers 19 in a predetermined pattern.

[0159] The second set of markers 19 in the alignment plate 18 includes a plurality of radiopaque markers equally spaced from one another in a circular pattern. In the illustrated embodiment, there are 24 evenly spaced markers in the alignment plate 18.

[0160] The first set of markers 17 in the orientation plate 16 includes a set of markers spaced apart from one another in a circular pattern, but the spacing between the markers is non-uniform. The circle formed by the markers 17 is smaller in diameter than the circle defined by the second set of markers 19 on the alignment plate 18. The two circles defined by the markers (the small circle defined by markers 17 and the large circle defined by markers 19) are coaxial and concentric with one another.

[0161] The first set of markers 17 also includes markers (e.g., two markers shown for each of the corresponding non-uniformly spaced markers) that extend radially outward from corresponding markers in a minor circle defined by the non-uniform markers such that an imaginary line from the center of the circle intersects the radially extending markers and the corresponding markers in the circle. In the illustrated embodiment, there are 24 markers 17 in the orientation plate 16 (eight markers on the minor circle and eight subsets of two markers that extend radially from the corresponding markers in the circle). It is important to note that the number of markers in both the alignment plate 18 and the orientation plate 16 is the same at 24.

[0162] All radiopaque markers may be in the form of stainless steel balls or BBs, but may be of any suitable radiopaque material.

[0163] The placement, size and number of radiopaque markers on the registration plate and orientation plate as described above provide optimal parameters for navigation accuracy, collimation requirements (i.e., the ability to detect sufficient markers and accurately place surgical implants even in the presence of collimation that truncates the pattern), minimization of anatomical obstruction to the surgeon during the navigated procedure, and orientation detection to allow the navigation tracking software to deterministically detect whether the image has been flipped 180 degrees or 90 degrees.

[0164] Although the radiolucent plates 14 are described with reference to the flat panel alignment fixture 2, they may be implemented as part of an alignment fixture (as shown in FIG. 18) configured to be mounted on the transmitter side of the imaging device.

[0165] The side frame has a plurality of optical tracking markers and is adapted to be removably attached to the base frame 6 without penetrating a sterile drape inserted between the base frame 6 and the side frame.

[0166] Each side frame includes six flat disk markers and six spherical markers in fixed relationship with the radiopaque markers, as shown in Figure 38. The side frames 8, 10 may be constructed from aluminum or any number of materials that provide appropriate strength, rigidity, weight, and optical properties for the system accuracy requirements.

[0167] The side frames 8, 10 may be bead blasted and black anodized to reduce potential reflections, among other surface treatment options. In the illustrated embodiment, the two side frames 8, 10 are oriented 180 degrees from each other and extend vertically from the base frame 6. Each side frame 8, 10 may include mounting features that allow for the use of both flat tracking disks 22 and spherical markers 24 (only posts are shown in FIG. 38) to allow for both NIR and visible light tracking.

[0168] The flat disk markers 22 and spherical markers 24 are interspersed with one another. In one embodiment, the pattern and spacing of the markers 22, 24 on one side frame 8 is identical to the pattern and spacing of the other side frame 10 when viewed from each side (i.e., 180 degrees from each other).

[0169] The side frames 8 , 10 are precisely self-aligned and oriented relative to the base frame 6 through the use of a kinematic mounting arrangement 12 .

[0170] Each side frame 8, 10 is designed to be non-interchangeable by incorporating physical keying features that prevent accidental incorrect installation by the user.

[0171] As shown in Figures 38, 41, and 42, the base frame 6 includes three spaced apart kinematic mount points 28 (recesses shown as three V-blocks) configured to self-align to corresponding kinematic mount points 26 (shown as three truncated spherical balls) on the base frame 6.

[0172] As shown in FIG. 42, the non-penetrating clamp 30 includes a rotating pin 34 and a cam handle 36 coupled to the rotating pin and configured to move or translate the U-shaped clamp 32 to press the U-shaped clamp against the base frame 6. The U-shaped clamp 32 has a slot 42 (see FIG. 43A) that receives a portion of the side frame 8 to allow translational or sliding movement relative to the side frame to compress or release the base frame 6. In an alternative embodiment as shown in FIG. 38, the U-shaped clamp 32 can be mounted over a side wall of the base frame 6 and a handle 38 having a threaded shaft 40 that is threadably coupled to the U-shaped clamp, such that rotation of the handle presses the U-shaped clamp against the base frame 6 to secure the side frame 8 to the base frame 6.

[0173] The first side frame 8 extends laterally on one side of the base frame 6 with its tracking markers 22, 24 facing away from the base frame 6 in a first direction away from the base frame, and the second side frame 10 extends laterally on the other side of the base frame 6 with its tracking markers 22, 24 facing away from the base frame 6 in a second direction opposite the first direction.

[0174] 38, the first and second side frames 8, 10 are parallel to each other when attached to the base frame 6. In the illustrated embodiment, the two side frames 8, 10 are attached perpendicular to the base frame 6.

[0175] In one embodiment, the spherical tracking markers 24 on the side frames 8, 10 are adapted to reflect infrared light (NIR) and the flat disk markers 22 are adapted to reflect visible light and in some embodiments also infrared light (NIR).

[0176] Several flexible ratchet strap configurations have been designed and implemented to facilitate attachment to a variety of flat panel C-arm detector housings.

[0177] FIG. 45 shows a ratchet strap assembly 46 including a pair of straps 48, 50, a pad assembly 52, and a ratchet 54 for attachment to a flat panel detector 4. FIG. 46 shows the base frame 6 of FIG. 38 attached to a flat panel detector 4 using the ratchet strap assembly 46 as shown in FIG. 45. One end of a first strap 50 is rotatably attached to the base frame 6 and the other end is attached to the ratchet 54 via the pad assembly 52. ​​One end of a second strap 48 (ladder strap) is rotatably coupled to the base frame 6 and the other end is coupled to the ratchet 54 for sliding adjustment relative to the first strap 50. The ratchet 54 allows the straps 48, 50 to be adjusted to fit over a variety of flat panel detectors 4. The ratchet strap assembly 46 is available, for example, from M2 Inc. (Colchester, VT). Straps 48, 50 extend from the base frame 6 and are configured to wrap around the underside of the flat panel detector 4 to temporarily secure the base frame 6 to the detector panel of the X-ray medical imaging device during use.

[0178] In one configuration, the first strap 50 of the ratchet strap assembly is comprised of an extension component that includes multiple through holes to facilitate adjustability (FIG. 45). In another configuration, one end of the first strap 50 is attached to a hook component, such as a spring-loaded carabiner attached to a ring or handle disposed behind the flat panel detector 4.

[0179] The flat panel detector alignment fixture 2 described above offers the following advantages.

[0180] Collimation of the images is possible while still allowing proper orientation and alignment fiducial marker detection for navigation and image processing requirements. Collimation has significant advantages in terms of image quality, since without such collimation visualization of the patient's anatomy in certain scenarios can be very difficult.

[0181] The optical tracking array is attached to a precision kinematic mount arrangement utilizing a clamp that prevents penetration of the sterile drape. The clamp is designed in a U-shape that is moved by either an integrated cam handle as an actuator or a threaded handle (acting as a lead screw) for rigid attachment to the base frame 6. Such an attachment method protects the integrity of the sterile drape.

[0182] The non-penetrating side frames 8, 10 with optical tracking markers facilitate separable, sterilizable, and autoclavable clamping of the side frames, unlike conventional designs that use a drape-penetrating mounting method. The side frames 8, 10 with optical tracking markers are separable from the base frame 6, utilize disposable markers, and are machine washable and autoclavable. The separable nature of the side frames 8, 10 allows for improved accuracy: optimization of size, segment length, and improved optimization for positioning against potential operating room obstacles.

[0183] The optical tracking array incorporates both passively tracked disks and spheres into a single frame assembly for ease of tracking utilizing NIR (spherical markers) and visible light technology (flat disk markers).

[0184] To facilitate image processing and navigation workflow, novel radiopaque fiducial patterns are incorporated into the orientation and registration plates.

[0185] The ratchet strap attachment configuration utilizes a non-deterministic compliant strap to facilitate attachment of the fluoroscopy fixture to various C-arm detector panel geometries. The ratchet strap includes an adjustable extension component that is fastened in series to a compliant pad with a spring-loaded mechanical ratchet that interacts with a flexible ladder strap belt assembly. The ladder strap may optionally include a hook or carabiner component for attachment to a tethered C-arm handle. Optional design safety elements incorporated into the belt assembly include hard stops.

[0186] The modular ratchet strap assembly has the ability to be adjusted around the circumference of the fluoroscopy fixture through the utilization of a self-locking clevis pin and incorporates a spring-loaded wedge or equivalent locating and self-locking feature. The incorporation of the clevis pin facilitates easy user adjustment of the ratchet strap assembly to account for various C-arm detector housings.

[0187] Compared to conventional fluoroscopy fixtures with plate separation distances of 100 mm or more, the spacing of the orientation and registration plates is minimized to 25 mm to 50 mm in one embodiment to minimize obstruction within the surgical working volume for the clinical team. This plate separation may be reduced or increased to increase precision, but is minimized to maximize the working space available to the clinical surgical team.

[0188] While the present invention has been disclosed in connection with the preferred embodiments shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art. Accordingly, the spirit and scope of the present invention is not intended to be limited by the foregoing examples, but is to be understood in the broadest sense permitted by law.

[0189] All documents referenced herein are hereby incorporated by reference.

Claims

1. 1. A registration fixture for use with a surgical navigation system for registration of a medical image into a three-dimensional tracking space, comprising: a base frame adapted to be mounted over a flat panel detector of an X-ray medical imaging device; a plate attached to the base frame, the plate having a first set of radiopaque markers embedded therein in a first predetermined pattern and a second set of radiopaque markers embedded therein in a second predetermined pattern; a side frame having a plurality of optical tracking markers, the side frame adapted to be removably attached to the base frame without penetrating a sterile drape when the sterile drape is inserted between the base frame and the side frame; a non-penetrating drape clamp that does not penetrate the sterile drape; The non-penetrating drape clamp comprises: a clamping position in which the non-penetrating drape clamp is pressed against the base frame to secure the side frame to the base frame; a clamping position in which the non-penetrating drape clamp is moved away from the base frame to release the base frame; an alignment fixture, the sterile drape being interposed between the base frame and the side frame when the non-penetrating drape clamp is in the clamped position;

2. The alignment fixture of claim 1 , wherein the side frames are attached to the base frame in a manner that constrains all six degrees of freedom.

3. The base frame includes at least three spaced kinematic mounting points; the side frames include kinematic mount points that are complementary to at least three spaced apart kinematic mount points on the base frame; The alignment fixture of claim 1 , wherein the kinematic mount points on the side frames are adapted to attach to corresponding kinematic mount points on the base frame.

4. 4. The alignment fixture of claim 3, wherein the at least three spaced apart kinematic mount points on the base frame include a plurality of recesses and the kinematic mount points on the side frames include a plurality of spherical balls adapted to self-align with the recesses.

5. The non-penetrating drape clamp comprises: a U-shaped clamp mountable on a side wall of the base frame; 4. The alignment fixture of claim 3, including a handle having a threaded shaft threadably coupled to the U-shaped clamp such that rotation of the handle presses the U-shaped clamp against the base frame to secure the side frame to the base frame.

6. The non-penetrating drape clamp comprises: a U-shaped clamp mountable on a side wall of the base frame; A rotating pin and a cam handle coupled to the rotation pin and configured to move the U-shaped clamp to press the U-shaped clamp against the base frame.

7. The side frame includes: a first side frame extending laterally on one side of the base frame and having tracking markers spaced apart facing away from the base frame in a first direction; a second side frame extending laterally on the other side of the base frame and having tracking markers spaced apart facing away from the base frame in a second direction opposite the first direction.

8. The alignment fixture of claim 7 , wherein the first side frame and the second side frame are parallel to one another when attached to the base frame.

9. The alignment fixture of claim 1 , wherein the optical tracking markers include a plurality of spaced apart spherical markers adapted to reflect light.

10. The alignment fixture of claim 1 , wherein the optical tracking markers include a plurality of spaced apart flat disk markers adapted to reflect light.

11. The optical tracking marker comprises: a plurality of spaced apart spherical markers adapted to reflect light; 10. The alignment fixture of claim 1 , comprising: a plurality of spaced apart flat disk markers adapted to reflect light.

12. The alignment fixture of claim 11 , wherein at least some of the spherical markers are interspersed with the flat disk markers.

13. 10. The alignment fixture of claim 1, further comprising at least one strap extending from the base frame and adapted to wrap around an underside of the flat panel detector of the X-ray medical imaging device to temporarily secure the base frame to the flat panel detector during alignment.

14. a first strap extending from one side of the base frame; a second strap extending from the other side of the base frame; 2. The alignment fixture of claim 1, further comprising: a ratchet coupled to the first strap and the second strap and adapted to adjust a length of the first strap relative to the second strap to temporarily secure the base frame to the flat panel detector of the X-ray medical imaging device during alignment.

15. 1. A registration fixture for use with a surgical navigation system for registration of a medical image into a three-dimensional tracking space, comprising: a base frame adapted to be mounted over a flat panel detector of an X-ray medical imaging device; a radiopaque plate attached to the base frame, the plate having a first set of radiopaque markers embedded therein in a predetermined pattern and disposed in a first plane, and a second set of radiopaque markers embedded therein in a predetermined pattern and disposed in a second plane, the second set of radiopaque markers being disposed above the first set of radiopaque markers; a side frame adapted to be removably attached to the base frame, the side frame having a plurality of optical tracking markers and a non-penetrating drape clamp adapted to clamp the side frame to the base frame without penetrating a sterile drape inserted between the side frame and the base frame; The non-penetrating drape clamp comprises: a clamping position in which the non-penetrating drape clamp is pressed against the base frame to secure the side frame to the base frame; a clamping position in which the non-penetrating drape clamp is moved away from the base frame to release the base frame; an alignment fixture, the sterile drape being interposed between the base frame and the side frame when the non-penetrating drape clamp is in the clamped position;

16. the base frame includes at least three spaced apart kinematic mounting points; the side frames include kinematic mount points that are complementary to at least three spaced apart kinematic mount points on the base frame; The alignment fixture of claim 15 , wherein the kinematic mount points on the side frames are adapted to attach to corresponding kinematic mount points on the base frame.

17. 17. The alignment fixture of claim 16, wherein the at least three spaced apart kinematic mount points on the base frame include a plurality of recesses and the kinematic mount points on the side frames include a plurality of spherical balls adapted to self-align with the recesses.

18. The non-penetrating drape clamp comprises: a U-shaped clamp mountable on a side wall of the base frame; 17. The alignment fixture of claim 16, including a handle having a threaded shaft threadably coupled to the U-shaped clamp such that rotation of the handle presses the U-shaped clamp against the base frame to secure the side frame to the base frame.

19. The non-penetrating drape clamp comprises: a U-shaped clamp mountable on a side wall of the base frame; A rotating pin and a cam handle coupled to the rotation pin and configured to move the U-shaped clamp to press the U-shaped clamp against the base frame.

20. The side frame includes: a first side frame extending laterally on one side of the base frame and having tracking markers spaced apart facing away from the base frame in a first direction; and a second side frame extending laterally on the other side of the base frame and having tracking markers spaced apart facing away from the base frame in a second direction opposite the first direction.

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