A surgical navigation system for partially occluded markers

Abstract

- Reference Zone (Z ref a surgical tool (1) having a reference marker (M1-M8); an optical tracker (T) arranged to track the orientation of the surgical tool (1) and having reference markers (M1-M8); and tot a stereo camera (2) arranged to capture images (20) of N fiducial markers (M1 to M8), tot a) a stereo camera (2) and a set of N images (20) captured by the stereo camera (2), where N is an integer greater than or equal to 4. tot Identify N fiducial markers (M1 to M8) tot a) determining the positions of fiducial markers (M1 to M8); and b) generating a set of patterns (P1 to P3), each pattern (P1 to P3) having M fiducial markers, where M is greater than or equal to 3 and exactly N. tot is an integer less than N, and the set of patterns (P1 to P3) includes N reference markers (M1 to M8), where N is N tot c) for each pattern (P1 to P3) of the set generated in step b), - extracting the positions of its corresponding M fiducial markers (M1 to M8) from step a); - calculating a reference zone (Z ref ) and d) applying the criteria to the set of patterns (P1-P3) to determine the reference zone (Z ref ) among the N reference markers (M1 to M8), and the criterion is to compare the poses of at least one partially occluded reference marker (M po 1. A surgical navigation system comprising: a data processor (DP) configured to perform the steps of: detecting the presence of a target object;

Description

[Technical Field]

[0001] The present invention relates to the technical field of surgical navigation systems.

[0002] The present invention is particularly applicable to navigating surgical tools during surgical intervention. [Background technology]

[0003] Surgical navigation systems known from the prior art include: - surgical instruments; an optical tracker arranged to track the pose of the surgical tool, the optical tracker having a fiducial marker; - a stereo camera arranged to capture images of the fiducial markers; - a data processor configured to identify fiducial markers from images captured by the stereo camera and determine positions of the fiducial markers; Equipped with.

[0004] When at least one of the fiducial markers is partially occluded (e.g., by physical intervention, coating defects, etc.), the two optical sensors of the stereo camera provide divergent information about the location of the corresponding fiducial marker. The data processor is configured to compare the information from the two optical sensors of the stereo camera by applying a criterion based on root-mean-square (RMS) deviation to complete image registration of the images captured by the stereo camera. The image registration is completed as long as the image registration error (i.e., the RMS error) is below a threshold.

[0005] Such prior art surgical navigation systems are not entirely satisfactory because completing image registration using the RMS error for the position of fiducial markers does not guarantee clinical relevance. In fact, it has been shown that deviations of several centimeters of the tip of a surgical instrument may not be detected by using the RMS error. This is due to the fact that non-occluded fiducial markers may compensate in the calculation of the RMS deviation of the position of partially occluded fiducial markers.

[0006] Those skilled in the art seek criteria that are more reliable and have relevant clinical meaning than RMS error for the location of partially occluded fiducial markers to improve the safety of navigation systems. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 5,828,770 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to overcome the above-mentioned drawbacks in whole or in part. [Means for solving the problem]

[0009] To this end, one subject of the present invention is a surgical tool having a reference zone; an optical tracker arranged to track the pose of the surgical tool, the optical tracker having a fiducial marker; - N tot a stereo camera arranged to capture images of N fiducial markers, tot is an integer greater than or equal to 4, and a) N images captured by a stereo camera tot Identify N fiducial markers totdetermining the positions of the fiducial markers; b) generating a set of patterns, each pattern having M reference markers, where M is greater than or equal to 3 and exactly N tot is an integer less than N, the set of patterns contains N reference markers, and N is N tot a step, which is an integer less than or equal to c) for each pattern in the set generated in step b), - extracting the positions of the corresponding M reference markers from step a); - calculating the pose of the reference zone in the reference coordinate system from the extracted positions of the corresponding M fiducial markers; d) applying a criterion to compare the poses of the reference zones calculated in step c) for the set of patterns, the criterion being designed to detect the presence of at least one partially occluded fiducial marker among the N fiducial markers; - a data processor configured to carry out the A surgical navigation system comprising:

[0010] Thus, such a surgical navigation system according to the present invention allows for reliable detection of the presence of at least one partially occluded fiducial marker by comparing the poses of a reference zone (e.g., the tip of a surgical instrument) that has clinical significance. More specifically, the criterion applied in step d) compares the poses of the reference zone calculated in step c) for the set of patterns.

[0011] Another subject of the invention is a surgical tool having a reference zone; an optical tracker arranged to track the pose of the surgical tool, the optical tracker having a fiducial marker; - N tot a stereo camera arranged to capture images of N fiducial markers, tot is an integer greater than or equal to 4, and a) N images captured by a stereo camera tot Identify N fiducial markers tot determining the positions of the fiducial markers; b) generating a set of patterns, each pattern having M reference markers, where M is greater than or equal to 3 and exactly N tot is an integer less than N, the set of patterns contains N reference markers, and N is N tot a step, which is an integer less than or equal to c) for each pattern in the set generated in step b), - extracting the positions of the corresponding M reference markers from step a); - calculating the pose of the reference zone in the reference coordinate system from the extracted positions of the corresponding M fiducial markers; c') extracting the positions of the N fiducial markers from step a) and calculating the pose of the reference zone in the reference coordinate system from the extracted positions of the N fiducial markers; d) applying a criterion to compare the pose of the reference zone calculated in step c') with the pose of the reference zone calculated in step c) for the set of patterns, the criterion being designed to detect the presence of at least one partially occluded reference marker among the N reference markers; - a data processor configured to carry out the A surgical navigation system comprising:

[0012] Thus, such a surgical navigation system according to the present invention allows for reliable detection of the presence of at least one partially occluded fiducial marker by comparing the pose of a reference zone (e.g., the tip of a surgical instrument) with a clinically relevant reference zone. More specifically, the criterion applied in step d) compares the pose of the reference zone calculated in step c') with the pose of the reference zone calculated in step c) for the set of patterns.

[0013] A surgical navigation system according to the present invention may include one or more of the following features.

[0014] According to one aspect of the present invention, - Stereo camera N tot arranged to capture images of N fiducial markers; tot is an integer greater than or equal to 5, - each pattern of the set of patterns generated in step b) has M reference markers, M being greater than or equal to 4 and exactly N tot is an integer less than - the data processor, if the criterion applied in step d) is met: e) for each pattern in the set generated in step b), - generating a set of subpatterns, each subpattern having m reference markers, where m is an integer equal to M-1; - calculating for each subpattern of the set the pose of a reference zone in the reference coordinate system from the positions of its corresponding m fiducial markers extracted in step c); - applying a criterion to compare between the calculated poses of the reference zone for the set of sub-patterns, the criterion being: N po If ≦M−3, then there are N within M reference markers of the corresponding pattern. po Place N partially occluded fiducial markers, po is the number of partially occluded fiducial markers, N po >M-3, N among M reference markers of the corresponding pattern po Detect the presence of partially occluded fiducial markers Designed to be The method is further configured to:

[0015] One advantage thus obtained is that step e) provides more information than simple presence detection. In fact, step e) poIf ≦M-3, then N po This allows for the placement of partially occluded fiducial markers.

[0016] Step e) is N po > In the case of M-3, N po However, in this case, step e) provides information about the amount of partially occluded fiducial markers. More specifically, step e) does not provide the exact number of partially occluded fiducial markers, but rather the number of partially occluded fiducial markers. po >The information M-3 can be given.

[0017] According to one aspect of the invention, a data processor includes: f1)N po If ≦M−3, then N placed in step e) po completing image registration of the images captured by the stereo cameras by removing the partially occluded fiducial markers; f2)N po If >M-3, then in step e) po stopping the surgical navigation if the presence of the partially occluded fiducial markers is detected; The method is further configured to perform the following steps:

[0018] One advantage thus obtained is to utilize the information obtained in step e). More specifically, on the one hand, N po If ≦M-3, then N po The locations of N partially occluded fiducial markers allow for reliable completion of image registration of images captured by a stereo camera. po The existence of N partially occluded fiducial markers po >If M-3, switch off surgical navigation for safety purposes.

[0019] According to one feature of the invention, each pattern of the set generated in step b) is selected according to the positions of its corresponding M reference markers relative to each other.

[0020] One advantage thus obtained is improved reliability of the criteria applied in step d).

[0021] According to one feature of the invention, the set of patterns generated in step b) satisfies a spread criterion that compares the relative positions of the M reference markers for each pattern of the set from the position determined in step a), the spread criterion being designed to find the minimum spatial spread between the M reference markers of a given pattern of the set.

[0022] One advantage thus obtained is improved reliability of the criteria applied in step d).

[0023] According to one feature of the invention, each pattern of the set generated in step b) is selected according to the position of its corresponding M reference markers relative to the stereo camera.

[0024] One advantage thus obtained is improved reliability of the criteria applied in step d).

[0025] According to one feature of the invention, the set of patterns generated in step b) satisfies a visibility criterion that compares the visibility levels of M reference markers among all patterns of the set from images captured by the stereo camera, the visibility criterion being designed to find the minimum visibility level at which the M reference markers of a given pattern of the set can be distinguished by the stereo camera within a predetermined margin of error.

[0026] One advantage thus obtained is improved reliability of the criteria applied in step d).

[0027] According to one feature of the invention, the set of patterns generated in step b) satisfies both a spread criterion and a visibility criterion.

[0028] One advantage thus obtained is that it maximizes the reliability of the criteria applied in step d).

[0029] According to one aspect of the invention, the data processor divides the integer number M of reference markers into N tot The device is configured to implement step b) by setting the .intg.value to an integer equal to -1.

[0030] So one advantage you get is that N tot The goal is to conserve the computational resources of the data processor by reducing the number of possible combinations of M reference markers. More specifically,

number

[0031]

number

[0032] According to one aspect of the invention, a data processor includes: b1) setting an integer number M of reference markers for each pattern in the set; b2) browsing all or a portion of the combinations of M reference markers from step a) to generate a pattern; and configured to perform step b).

[0033] According to one aspect of the invention, a data processor includes: b3) selecting a set of patterns from the patterns generated in step b2) that satisfy a spread criterion. The method is configured to perform the following steps.

[0034] One advantage thus obtained is improved reliability of the criteria applied in step d).

[0035] According to one aspect of the invention, a data processor includes: b'3) selecting a set of patterns from the patterns generated in step b2) that satisfy a visibility criterion; The method is configured to perform the following steps.

[0036] One advantage thus obtained is improved reliability of the criteria applied in step d).

[0037] According to one aspect of the invention, a data processor includes: b"3) selecting a set of patterns from the patterns generated in step b2) that meet both the spread criterion and the visibility criterion; The method is configured to perform the following steps.

[0038] One advantage thus obtained is that it maximizes the reliability of the criteria applied in step d).

[0039] According to one feature of the invention, the criterion applied in step d) is a spread criterion.

[0040] Thus, one advantage gained is simplicity of implementation.

[0041] According to one aspect of the invention, the spread criterion is: - detecting a minimum spatial spread between the poses of the reference zones calculated in step c) for the set of patterns to detect the presence of at least one partially occluded fiducial marker among the N fiducial markers; - detecting the minimum spatial spread between the pose of the reference zone calculated in step c') and each pose of the reference zone calculated in step c), and detecting the presence of at least one partially occluded fiducial marker among the N fiducial markers; It is designed to be.

[0042] definition The term "surgical tool" is understood to mean an object used in surgery. A surgical tool may be an instrument or an implant.

[0043] The term "fiducial marker" is understood to mean a marker that is used in combination with a stereo camera to locate the position and orientation of a surgical tool. The fiducial marker is preferably an optical marker. The optical marker preferably performs near-infrared optical tracking in combination with a stereo camera. The fiducial marker may be selected from colored marks, textured marks, geometric patterns, retro-reflective markers, coded objects, and scale bars.

[0044] The term "reference zone" is understood to mean a spatial area that allows a user (e.g., a surgeon) to obtain appropriate information about the orientation of a surgical tool. The reference zone may be the tip of the surgical tool.

[0045] The term "posture" is understood to mean position and spatial orientation.

[0046] - The term "capturing images of fiducial markers" is understood to mean that at a given time, each fiducial marker captured by the stereo camera is either fully visible or partially visible in the image, except in cases where the fiducial marker is fully occluded (i.e., not visible at all by the stereo camera).

[0047] - The term "partially occluded" is understood to mean that at a given time, the fiducial marker is partially visible (but not completely) in the images captured by the stereo camera. (i) Partial obscuration caused by an object or person between the fiducial marker and the stereo camera; (ii) Partial obscuration caused by covering the fiducial marker (e.g., blood splatter, mechanical defects, mechanical damage, etc.). This can be attributed to:

[0048] - The term "data processor" is understood to mean a device such as a calculator or computer that performs operations on data.

[0049] - The term "generate" is understood to mean either the original (gross) production of patterns (or sub-patterns) that may or may not be subjected to further selection, or the already filtered production of patterns (or sub-patterns) that have undergone selection.

[0050] - the term "comprises N fiducial markers" means that the set of patterns generated in step b) collectively covers N fiducial markers, where N is N tot It is understood to mean an integer less than or equal to:

[0051] The term "reference coordinate system" is understood to mean a geometric reference frame used to indicate the pose of an object that can be obtained by three-dimensional geometric reconstruction.

[0052] The term "detect the presence" is understood to mean that the presence of at least one partially obscured fiducial marker is revealed, but does not necessarily imply that the at least one partially obscured fiducial marker can be positioned.

[0053] Other features and advantages will become apparent in the detailed description of various embodiments of the invention, which description includes reference to examples and the accompanying drawings. [Brief explanation of the drawings]

[0054] [Figure 1] FIG. 1 is a partial schematic perspective view of a surgical navigation system according to the present invention in an operating room, showing the presence of a robotic arm (data processor not shown). [Figure 2] 1 is a flow chart illustrating a first embodiment of steps performed by a data processor comprising a surgical navigation system according to the present invention. [Figure 3] 10 is a flow chart illustrating a second embodiment of steps performed by a data processor comprising a surgical navigation system according to the present invention. [Figure 4] 10 is a flowchart illustrating a third embodiment of steps performed by a data processor comprising a surgical navigation system according to the present invention. [Figure 5] 10 is a flowchart illustrating a fourth embodiment of steps performed by a data processor comprising a surgical navigation system according to the present invention. [Figure 6] 10 is a flowchart illustrating a fifth embodiment of steps performed by a data processor comprising a surgical navigation system according to the present invention. [Figure 7] 10 is a flowchart illustrating a sixth embodiment of steps performed by a data processor comprising a surgical navigation system according to the present invention. [Figure 8] Schematic top view of Ntot (=8) fiducial markers captured by a stereo camera in the absence of partially occluded fiducial markers. [Figure 9] Schematic top view of a set of three patterns (each pattern having four fiducial markers) generated by a data processor equipped with surgical navigation according to the present invention, showing a comparison between the poses of the reference zones calculated in step c) for the set of three patterns in the absence of partially occluded fiducial markers. [Figure 10] Schematic top view of a set of three patterns (each pattern having four fiducial markers) generated by a data processor equipped with surgical navigation according to the present invention, showing a comparison of the reference zone pose calculated in step c') with the reference zone pose calculated in step c) for the set of three patterns in the absence of a partially occluded fiducial marker. [Figure 11] Schematic top view of Ntot (=8) fiducial markers captured by a stereo camera in the presence of partially occluded fiducial markers. [Figure 12] Schematic top view of a set of three patterns (each pattern having four fiducial markers) generated by a data processor equipped with surgical navigation according to the present invention, showing a comparison between the poses of the reference zones calculated in step c) for the set of three patterns in the presence of partially occluded fiducial markers. [Figure 13] Schematic top view of a set of three patterns (each pattern having four fiducial markers) generated by a data processor equipped with surgical navigation according to the present invention, showing a comparison of the reference zone pose calculated in step c') with the reference zone pose calculated in step c) for the set of three patterns in the presence of partially occluded fiducial markers. [Figure 14] FIG. 10 is a schematic top view illustrating the generation of a set of four sub-patterns (each sub-pattern having three fiducial markers) when step e) is performed by a data processor equipped with surgical navigation according to the present invention. [Figure 15] FIG. 10 is a schematic top view of a set of four sub-patterns (each sub-pattern having three fiducial markers) showing a comparison between the poses of the reference zones calculated in step e) for the set of four sub-patterns. DETAILED DESCRIPTION OF THE INVENTION

[0055] The format used for Figures 2-7 conforms to ISO standard 5807 for flowcharts. "Y" means "yes," i.e., the test result is true. "N" means "no," i.e., the test result is false.

[0056] It should be noted that for ease of reading and understanding, the drawings described above are schematic and not necessarily to scale.

[0057] Elements that are identical or provide the same functionality will be carried by the same reference symbols across the various embodiments for the sake of brevity.

[0058] One subject of the present invention is - Reference Zone Z ref a surgical tool 1 having an optical tracker T arranged to track the orientation of the surgical tool 1 and having reference markers M1 to M8; - N tot a stereo camera 2 arranged to capture images 20 of N fiducial markers M1 to M8, tot is an integer greater than or equal to 4, and there are two stereo cameras. a) Images 20 to N captured by stereo camera 2 tot Identify the reference markers M1 to M8 and tot determining the positions of the fiducial markers M1 to M8; b) generating a set of patterns P1 to P3, each pattern P1 to P3 having M reference markers, where M is greater than or equal to 3 and exactly N; tot is an integer less than N, and the set of patterns P1 to P3 includes N reference markers M1 to M8, and N is N tot a step, which is an integer less than or equal to c) for each pattern P1 to P3 of the set generated in step b), - extracting the positions of the M corresponding reference markers M1 to M8 from step a); - A reference zone Z in the reference coordinate system from the extracted positions of the corresponding M fiducial markers M1 to M8 refcalculating the pose of d) Applying the criteria, the reference zone Z calculated in step c) for the set of patterns P1 to P3 ref a step of comparing the postures of at least one partially occluded reference marker M among the N reference markers M1 to M8; po a step designed to detect the presence of - a data processor DP configured to implement A surgical navigation system comprising:

[0059] Another subject of the invention is - Reference Zone Z ref a surgical tool 1 having an optical tracker T arranged to track the orientation of the surgical tool 1 and having reference markers M1 to M8; - N tot a stereo camera 2 arranged to capture images 20 of N fiducial markers M1 to M8, tot is an integer greater than or equal to 4, and there are two stereo cameras. a) Images 20 to N captured by stereo camera 2 tot Identify the reference markers M1 to M8 and tot determining the positions of the fiducial markers M1 to M8; b) generating a set of patterns P1 to P3, each pattern P1 to P3 having M reference markers M1 to M8, where M is greater than or equal to 3 and exactly N; tot is an integer less than N, and the set of patterns P1 to P3 includes N reference markers M1 to M8, and N is N tot a step, which is an integer less than or equal to c) for each pattern P1 to P3 of the set generated in step b), - extracting the positions of the M corresponding reference markers M1 to M8 from step a); - A reference zone Z in the reference coordinate system from the extracted positions of the corresponding M fiducial markers M1 to M8 ref calculating the pose of c') Extract the positions of the N fiducial markers M1 to M8 from step a), and calculate a reference zone Z in the reference coordinate system from the extracted positions of the N fiducial markers M1 to M8. ref calculating the pose of d) Applying the criteria, the reference zone Z calculated in step c') ref The reference zone Z calculated in step c) for the set of postures and patterns P1 to P3 ref a step of comparing the posture of at least one partially occluded reference marker M among the N reference markers M1 to M8 with the posture of the reference marker M po a step designed to detect the presence of - a data processor DP configured to implement A surgical navigation system comprising:

[0060] surgical tools The surgical tool 1 can be an instrument, an implant, or a surgical table.

[0061] As a non-limiting example, surgical tool 1 may be a Cobb spine elevator. A Cobb spine elevator is a specialized instrument for neurosurgical procedures. It may be used to elevate spinal components in procedures requiring exploration of the spinal column. For example, it may be used to separate the ligamentum flavum from the lamina or the intervertebral disc from the associated vertebra. Additionally, the Cobb spine elevator features a semi-sharp blade and a slight curve, making it well-suited for minimally traumatic exploration of delicate soft tissue areas.

[0062] As another example, surgical tool 1 may be a trocar, such as a spinal trocar. Surgical tool 1 may be a powered surgical tool, such as a powered drill, powered saw, powered burr or mill, ultrasonic milling device, radiofrequency, microwave or cryocautery needle, or any device capable of interacting with the anatomical structure being treated.

[0063] As another example, the surgical tool 1 may be an orthopedic implant such as a pedicular screw, a hip implant, a knee implant or a shoulder implant.

[0064] The surgical tool 1 is placed in a reference zone Z, which is a spatial region that allows a user (e.g., a surgeon) to obtain appropriate information about the orientation of the surgical tool 1. ref As a non-limiting example, the reference zone Z ref When the surgical tool 1 is an instrument, this may be the tip of the surgical tool 1.

[0065] Robotic Arm The surgical tool 1 may be attached to a robotic arm 3 for assisting a user (e.g., a surgeon) during a surgical intervention. For example, in spinal surgery, a user may need to implant one or more screws into at least one vertebra. The robotic arm 3 may assist the user by holding a drill guide and maintaining the drill guide according to a planned axis. Thus, the user can drill holes intended to receive screws into the vertebra along the planned axis using a hand-held drill passing through the drill guide held by the robotic arm 3. The patient may be equipped with an optical tracker T. The robotic arm 3 may be servo-controlled relative to the movement of the optical tracker T on the patient to maintain alignment with the entry point location on the patient's bone, compensating for any movement of the bone due to the patient's breathing or any mechanical interaction.

[0066] The robotic arm 3 may be disposed on a cart. The cart may be movable on wheels and may include at least one handle that allows an operator to easily maneuver and transport the robotic arm 3. The cart may be manually operated or alternatively may be motorized with at least one degree of freedom. At least one of the wheels may be blocked when the cart is moved to a desired position relative to the operating table. The cart may include switches such as a power switch, an emergency button, etc.

[0067] Robot Arm 3 a proximal end 30 extending from a base 300; a distal end 31 opposite the proximal end 30; may have:

[0068] The robot arm 3 may be equipped with an end effector 32 attached to a distal end 31. The end effector 32 may include a hand grip and a tool guide 320. The hand grip is configured to be held by a user's hand to operate the robot arm 3. The hand grip may include first and second switches configured to be separately actuated by a user to trigger an operating mode of the robot arm 3. The switches may include push buttons, resistive switches, piezoelectric switches, etc. Although the switches may be disposed in another portion of the robot arm 3, the switches are preferably disposed on the hand grip so that a user can use one hand to actuate one of the switches and simultaneously handle the end effector 32 to move the robot arm 3 (in hand-guided mode) or follow the movement of the robot arm 3 (in calculated trajectory mode). The hand grip may include at least one user interface configured to provide information about the current mode. Although the user interface may be disposed within another portion of the robotic arm 3, the user interface is advantageously located on or near the hand grip, allowing a user to focus on the end effector 32 as the robotic arm 3 is manipulated. The user interface may include a display having graphical items (e.g., text, marks having variable colors, etc.) that change depending on the current mode. The user interface may include a plurality of light-emitting diodes configured to have predetermined colors and / or flashing conditions depending on the current mode. The light-emitting diodes may be arranged as a ring around or near the hand grip.

[0069] The robotic arm 3 may be equipped with a controller configured to controllably move the robotic arm 3 according to a predetermined trajectory. The controller may include a processor, a data storage device, and a communication device. The controller may be configured to controllably move at least a portion of the cart (e.g., at least one wheel). The controller may be incorporated within the cart. Alternatively, the controller may be provided separately from the cart and configured to communicate with the robotic arm 3 wirelessly or via a wire.

[0070] The robot arm 3 has multiple degrees of freedom in translation and / or rotation. Typically, the robot arm 3 has at least five, preferably six or seven, motorized degrees of freedom. Therefore, the robot arm 3 has multiple articulated segments driven by motors. The robot arm 3 can be, for example, an LBR Med™ robot provided by KUKA (Germany). The robot arm 3 can be controlled in an autonomous mode depending on the desired object and trajectory. Alternatively, the robot arm 3 can be operated using a collaborative mode (cobot). As another alternative, the robot arm 3 can be remotely controlled using a master controller. A combination of these different modes can be used for the robot arm 3.

[0071] The robotic arm 3 may be active in the sense that it holds and moves the powered surgical tool 1, which directly interacts with the anatomical structure. In contrast, the robotic arm 3 may be passive in the sense that it holds the tool guide 320 within a predefined position relative to the anatomical structure into which the powered surgical tool 1 is inserted by the surgeon. For example, a powered drill may be attached to the tool guide 320 to actively drill bone along a predefined path until the endpoint of a selected linear trajectory is reached. As another example, a powered burr may be used to remove a bone volume where a tumor has been detected, and the robotic arm 3 is controlled to cause the burr tip to execute a 3D complex path trajectory corresponding to the bone volume to be removed.

[0072] Optical Tracker The optical tracker T is arranged to track the orientation of the surgical tool 1. For this purpose, the optical tracker T has fiducial markers M1-M8. The orientation of the surgical tool 1 may be defined by three positional parameters and three orientational parameters. As a non-limiting example, the fiducial markers M1-M8 may be reflective markers designed to reflect infrared radiation. The reflective markers may have a spherical shape.

[0073] Optical tracker T may be removably or permanently mounted on surgical tool 1, for example, by mechanical or magnetic attachment. Optical tracker T may be disposed on tool guide 320 and track the orientation of surgical tool 1 from a known longitudinal axis, which is the guide axis of tool guide 320. Optical tracker T may be removably or permanently mounted on tool guide 320, for example, by mechanical or magnetic attachment.

[0074] Stereo Camera The stereo camera 2 makes it possible to provide depth information in a compact way.

[0075] The stereo camera 2 may incorporate a light source (for reasons of compactness) configured to emit infrared radiation. The light source may comprise a set of light-emitting diodes. Alternatively, the light source may belong to a dedicated infrared illuminator.

[0076] The stereo camera 2 is advantageously configured to detect infrared radiation. tot The image capturing device is arranged to capture images 20 of the fiducial markers M1 to M8, and tot is an integer greater than or equal to 4. The stereo camera 2 is advantageously arranged to detect infrared radiation reflected by the reflective markers of the optical tracker T.

[0077] N tot The captured image 20 of the fiducial markers M1-M8 may be a two-dimensional image in grey-tone or black and white (by applying a saturation threshold).

[0078] The stereo camera 2 may comprise a support 21 mounted on a rolling stand 22. The rolling stand 22 may include a telescopic rod 220 defining an axis. The support 21 of the stereo camera 2 is advantageously movable in rotation about the axis of the telescopic rod 220. The support 21 of the stereo camera 2 is advantageously movable in translation along the axis of the telescopic rod 220.

[0079] Data Processor The data processor DP is a device such as a calculator or computer that performs operations on data. The data processor DP is advantageously integrated within the stereo camera 2.

[0080] Step a) The data processor DP processes N images 20 to 21 captured by the stereo camera 2. tot Identify the reference markers M1 to M8 and tot The method is configured to perform a step a) of determining the positions of the reference markers M1 to M8.

[0081] As a non-limiting example, the data processor DP may implement a position estimation algorithm known from the prior art, as described inter alia in US Pat. No. 5,828,770.

[0082] Step b) The data processor DP generates a set of patterns P1 to P3, each pattern P1 to P3 having M reference markers, where M is greater than or equal to 3 and exactly N. tot is an integer less than N, and the set of patterns P1 to P3 includes N reference markers M1 to M8, and N is N tot The set of patterns generated in step b) collectively covers N reference markers, where N is an integer less than or equal to N tot In other words, the set of patterns generated in step b) is equal to or less than the N tot It covers all or some of the reference markers M1 to M8.

[0083] Each pattern P1-P3 of the set generated in step b) is advantageously selected according to the relative positions of the M fiducial markers M1-M8 relative to one another. In other words, the relative positions of the M fiducial markers M1-M8 of a given pattern P1-P3 are compared between them to select the given pattern P1-P3. To this end, the set of patterns P1-P3 generated in step b) advantageously satisfies a spread criterion that compares the relative positions of the M fiducial markers M1-M8 for each pattern P1-P3 of the set from the positions determined in step a), the spread criterion being designed to detect the minimum spatial spread between the M fiducial markers M1-M8 of a given pattern P1-P3 of the set. As a non-limiting example, the relative positions of the M fiducial markers M1-M8 of a given pattern P1-P3 define the maximum distance between two fiducial markers. A given pattern P1-P3 of the set may be selected if the maximum distance exceeds a first predetermined threshold corresponding to a first minimum spatial extent. As another example, a secondary distance may be defined between the line formed by the two fiducial markers (defining the maximum distance) and another fiducial marker of the given pattern P1-P3 of the set. A given pattern P1-P3 may be selected if the secondary distance exceeds a second predetermined threshold corresponding to a second minimum spatial extent. Alternatively, a given pattern P1-P3 of the set may define a centroid and be selected if the distance between its fiducial marker M1-M8 and the centroid exceeds a third predetermined threshold corresponding to a third minimum spatial extent. As another alternative, the fiducial markers M1-M8 of a given pattern P1-P3 form vertices defining a surface. A given pattern P1-P3 may be selected if the surface exceeds an area threshold.

[0084] Each pattern P1-P3 of the set generated in step b) is advantageously selected according to the position of its corresponding M reference markers M1-M8 relative to the stereo camera 2. To this end, the set of patterns P1-P3 generated in step b) advantageously satisfies a visibility criterion that compares the visibility levels of the M reference markers M1-M8 among all patterns P1-P3 of the set from the image 20 captured by the stereo camera 2, the visibility criterion being designed to find the minimum visibility level at which the M reference markers M1-M8 of a given pattern P1-P3 of the set are distinguished by the stereo camera 2 within a predetermined margin of error. As a non-limiting example, the minimum visibility level may preferably result in a viewing angle of 50°.

[0085] The set of patterns P1 to P3 generated in step b) advantageously meets both the spread and visibility criteria.

[0086] Data Processor DP b1) setting an integer M of reference markers M1 to M8 for each pattern P1 to P3 of the set; b2) browsing all or some of the combinations of M reference markers M1 to M8 from step a) to generate patterns P1 to P3; may be configured to perform step b).

[0087] Data Processor DP b3) selecting a set of patterns P1 to P3 that satisfy a spread criterion from the patterns generated in step b2). The method may be configured to implement the following:

[0088] Alternatively, the data processor DP b'3) selecting a set of patterns P1 to P3 that satisfy a visibility criterion from the patterns generated in step b2); The method may be configured to implement the following:

[0089] Another alternative is the Data Processor DP. b"3) selecting a set of patterns P1 to P3 that satisfy both the spread criterion and the visibility criterion from the patterns generated in step b2); The method is advantageously configured to perform the following steps:

[0090] The data processor DP calculates the integer M of the reference markers M1 to M8 as N tot The method is advantageously configured to implement step b) by setting the num_value to an integer equal to -1.

[0091] Step c) The data processor DP performs step c) for each pattern P1 to P3 of the set generated in step b), i.e. - extracting the positions of the M corresponding reference markers M1 to M8 from step a); - A reference zone Z in the reference coordinate system from the extracted positions of the corresponding M fiducial markers M1 to M8 ref and calculating the attitude of The method is configured to perform the following steps.

[0092] Reference Zone Z ref The pose of the marker M1-M8 can be calculated from the extracted positions of the corresponding M fiducial markers M1-M8 by using a matrix transformation between the coordinate systems. The matrix transformation can be a rigid transformation, which refers to a geometric transformation in Euclidean space that preserves the Euclidean distance between all pairs of points. The rigid transformation can include rotation, translation, reflection, or a combination thereof.

[0093] As a non-limiting example, the data processor DP may calculate a reference zone Z from the extracted positions of the corresponding M fiducial markers M1 to M8. ref The Kabsch-Umeyama algorithm can be implemented to calculate the pose of

[0094] Step c') The data processor DP extracts the positions of the N fiducial markers M1 to M8 from step a) and calculates a reference zone Z in the reference coordinate system from the extracted positions of the N fiducial markers M1 to M8. ref The method may be configured to perform a step c') of calculating the attitude of the

[0095] Reference Zone Z ref The pose of the N fiducial markers M1-M8 can be calculated from the extracted positions of the N fiducial markers M1-M8 by using a matrix transformation between coordinate systems. The matrix transformation can be a rigid transformation, which refers to a geometric transformation in Euclidean space that preserves the Euclidean distance between all pairs of points. The rigid transformation can include rotation, translation, reflection, or a combination thereof.

[0096] As a non-limiting example, the data processor DP may calculate a reference zone Z from the extracted positions of the N fiducial markers M1 to M8. ref The Kabsch-Umeyama algorithm can be implemented to calculate the pose of

[0097] Step d) As shown in FIG. 2, in one embodiment, the data processor DP applies the criteria to the reference zone Z calculated in step c) for the set of patterns P1 to P3. ref and step d) comparing the postures of the N reference markers M1 to M8, wherein the criterion is whether at least one partially occluded reference marker M po Step d) is configured to perform step d), which is designed to detect the presence of N tot The step d) is carried out by the data processor DP insofar as the images 20 of the fiducial markers M1 to M8 are captured by the stereo camera 2. The criterion applied in step d) is advantageously a spread criterion. The spread criterion applied in step d) is the spread of the reference zone Z calculated in step c) for the set of patterns P1 to P3. ref and at least one partially occluded fiducial marker M among the N fiducial markers M1 to M8 is advantageously designed to detect the minimum spatial spread between the poses of the poDetect the presence of

[0098] In other words, as shown in FIGS. 9 and 12, step d) calculates the reference zone Z calculated in step c) for the set of patterns P1 to P3. ref 9, the reference zone Z calculated in step c) for the set of patterns P1 to P3 can be compared between the positions Z1, Z2, and Z3 of the reference zone Z ref The positions Z1, Z2, Z3 of the partially occluded fiducial marker M po As shown in FIG. 12, the reference zone Z calculated in step c) for the set of patterns P1 to P3 ref The positions Z1, Z2, Z3 of the partially occluded fiducial marker M po Indicates the presence of

[0099] In another embodiment, as shown in FIG. 3, when step c') is performed, the data processor DP applies the criteria to the reference zone Z calculated in step c'). ref The reference zone Z calculated in step c) for the set of postures and patterns P1 to P3 ref and step d) comparing the posture of at least one partially occluded reference marker M among the N reference markers M1 to M8. po Step d) is configured to perform step d), which is designed to detect the presence of N tot Insofar as the images 20 of the fiducial markers M1 to M8 are captured by the stereo camera 2, this is carried out by the data processor DP. The criterion applied in step d) is advantageously a spread criterion. If step c') is carried out by the data processor DP, the spread criterion applied in step d) is the spread of the reference zone Z calculated in step c'). ref and the reference zone Z calculated in step c). refand at least one partially occluded fiducial marker M among the N fiducial markers M1 to M8. po Detect the presence of

[0100] In other words, as shown in Figures 10 and 13, step d) calculates the reference zone Z calculated in step c'). ref and the reference zone Z calculated in step c) for the set of patterns P1 to P3. ref As shown in FIG. 10, this can be done by comparing the positions Z1, Z2, Z3 of the reference zone Z calculated in step c'). ref and the reference zone Z calculated in step c). ref The positions Z1, Z2, Z3 of the partially occluded fiducial marker M po As shown in FIG. 13, the reference zone Z calculated in step c') ref and the reference zone Z calculated in step c). ref The positions Z1, Z2, and Z3 of the partially occluded fiducial marker M po Indicates the presence of

[0101] Step e) As shown in Figures 4 and 5, the following conditions are met: - Stereo camera 2 N tot The image capturing device is arranged to capture images 20 of the fiducial markers M1 to M8, and tot is an integer greater than or equal to 5, - each pattern P1 to P3 of the set of patterns generated in step b) has M reference markers M1 to M8, M being greater than or equal to 4 and exactly N tot is an integer less than When is satisfied, The data processor DP then, if the criterion applied in step d) is satisfied, e) for each pattern P1 to P3 of the set generated in step b), - generating a set of sub-patterns SP1 to SP4 (shown in FIG. 14), each sub-pattern SP1 to SP4 having m reference markers M1 to M8, where m is an integer equal to M-1; - a reference zone Z in the reference coordinate system for each subpattern SP1 to SP4 of the set from the positions of its corresponding m fiducial markers M1 to M8 extracted in step c) ref calculating the pose of - Apply the criteria to the set of subpatterns SP1 to SP4 and find the reference zone Z ref a step of comparing the calculated poses of N po If ≦M−3, then N is included in the M reference markers M1 to M8 of the corresponding patterns P1 to P3. po Partially occluded fiducial markers M po Place N po is a partially occluded fiducial marker M po is the number of N po >M-3, N in M ​​reference markers M1 to M8 of the corresponding patterns P1 to P3 po Partially occluded fiducial markers M po Detect the presence of Designed to be Advantageously, the method is further configured to perform the following steps:

[0102] Reference Zone Z ref The pose of the m-point markers M1-M8 can be calculated from the extracted positions of the m fiducial markers M1-M8 by using a matrix transformation between coordinate systems. The matrix transformation can be a rigid transformation, which refers to a geometric transformation in Euclidean space that preserves the Euclidean distance between all pairs of points. The rigid transformation can include rotation, translation, reflection, or a combination thereof.

[0103] As a non-limiting example, the data processor DP may calculate a reference zone Z from the extracted positions of the m fiducial markers M1 to M8. ref The Kabsch-Umeyama algorithm can be implemented to calculate the pose of

[0104] For the set of subpatterns SP1 to SP4, refer to zone Z. ref The criterion applied in step e) to compare between the calculated poses of N is advantageously a spread criterion. po = M-3, the reference zone Z calculated in step e) for the set of subpatterns SP1 to SP4 ref Positions Z11, Z12, Z13, and Z14 of the image plane exceed the spread threshold between them. More specifically, the furthest position Z14 is located at the partially occluded fiducial marker M po Therefore, the partially obscured reference marker M1 of the corresponding pattern P1 that is not included in the subpattern SP4 is obtained. po It is possible to place

[0105] the reference zone Z calculated in step e) for the set of subpatterns SP1 to SP4 ref If positions Z11, Z12, Z13, and Z14 of N do not exceed the spread threshold between them, po >M-3 is N po Partially occluded fiducial markers M po The presence of these partially hidden fiducial markers is revealed, but these partially hidden fiducial markers cannot be located.

[0106] Step e) is N tot As long as the images 20 of the fiducial markers M1 to M8 are captured by the stereo camera 2, this is performed by the data processor DP.

[0107] Steps f1) and f2) As shown in Figures 6 and 7, when step e) is performed by a data processor DP, the data processor DP f1)N po If ≦M−3, then N placed in step e) po Partially occluded fiducial markers M pocompleting the image registration of the images 20 captured by the stereo camera 2 by removing f2)N po If >M-3, then in step e) po Partially occluded fiducial markers M po and stopping the surgical navigation if the presence of the Advantageously, the method is further configured to perform the following steps:

[0108] Step f1) is N tot As long as the images 20 of the fiducial markers M1 to M8 are captured by the stereo camera 2, this is performed by the data processor DP.

[0109] The invention is not limited to the described embodiments: a person skilled in the art is able to consider all technically feasible combinations thereof and to substitute them with equivalents.

Claims

1. - Reference Zone (Z ｒｅｆ a surgical instrument (1) having a an optical tracker (T) arranged to track the orientation of said surgical tool (1) and having reference markers (M1 to M8); -N ｔｏｔ a stereo camera (2) arranged to capture images (20) of N fiducial markers (M1-M8), ｔｏｔ is an integer greater than or equal to 4, and a stereo camera (2); a Data Processor (DP), a) extracting the N images (20) from the images (20) captured by the stereo camera (2) ｔｏｔ Identify the N reference markers (M1 to M8) ｔｏｔ determining the positions of fiducial markers (M1-M8); b) generating a set of patterns (P1-P3), each pattern (P1-P3) having M reference markers, where M is greater than or equal to 3 and exactly N; ｔｏｔ is an integer less than N, and said set of patterns (P1-P3) includes N reference markers (M1-M8), and N is N ｔｏｔ a step, which is an integer less than or equal to c) for each pattern (P1-P3) of the set generated in step b), extracting the positions of said M reference markers (M1 to M8) corresponding to them from step a); - Calculate the reference zone (Z) in the reference coordinate system from the extracted positions of the corresponding M fiducial markers (M1 to M8). ｒｅｆ ) pose calculation; d) applying the criteria to the reference zone (Z) calculated in step c) for the set of patterns (P1-P3) ｒｅｆ ) among the N reference markers (M1-M8), and the criterion is the presence or absence of at least one partially occluded reference marker (M ｐｏ ) and a data processor (DP) configured to implement A surgical navigation system comprising:

2. - Reference Zone (Z ｒｅｆ a surgical instrument (1) having a an optical tracker (T) arranged to track the orientation of said surgical tool (1) and having reference markers (M1 to M8); -N ｔｏｔ a stereo camera (2) arranged to capture images (20) of N fiducial markers (M1-M8), ｔｏｔ is an integer greater than or equal to 4, and a stereo camera (2); a Data Processor (DP), a) extracting the N images (20) from the images (20) captured by the stereo camera (2) ｔｏｔ Identify the N reference markers (M1 to M8) ｔｏｔ determining the positions of fiducial markers (M1-M8); b) generating a set of patterns (P1-P3), each pattern (P1-P3) having M reference markers (M1-M8), where M is greater than or equal to 3 and exactly N; ｔｏｔ is an integer less than N, and said set of patterns (P1-P3) includes N reference markers (M1-M8), and N is N ｔｏｔ a step, which is an integer less than or equal to c) for each pattern (P1-P3) of the set generated in step b), extracting the positions of said M reference markers (M1 to M8) corresponding to them from step a); - Calculate the reference zone (Z) in the reference coordinate system from the extracted positions of the corresponding M fiducial markers (M1 to M8). ｒｅｆ ) pose calculation; c') extracting the positions of the N fiducial markers (M1 to M8) from step a), and calculating the reference zone (Z ｒｅｆ ) pose calculation; d) applying the criteria to the reference zone (Z ｒｅｆ ) and the set of patterns (P1-P3) of the reference zone (Z ｒｅｆ ) among the N reference markers (M1-M8), ｐｏ ) and a data processor (DP) configured to implement A surgical navigation system comprising:

3. - the stereo camera (2) is N ｔｏｔ arranged to capture images (20) of fiducial markers (M1-M8); ｔｏｔ is an integer equal to or greater than 5, each pattern (P1 to P3) of said set of patterns generated in step b) has M reference markers (M1 to M8), M being greater than or equal to 4 and exactly N ｔｏｔ is an integer less than said data processor (DP) if the criterion applied in step d) is satisfied, e) for each pattern (P1-P3) of the set generated in step b), generating a set of sub-patterns (SP1 to SP4), each having m reference markers (M1 to M8), where m is an integer equal to M-1; - for each sub-pattern (SP1 to SP4) of the set, the reference zone (Z ｒｅｆ ) pose calculation; - Applying the criteria to determine the reference zone (Z) for the set of sub-patterns (SP1 to SP4) ｒｅｆ ) comparing the calculated poses of the N ｐｏ If ≦M−3, then N is included in the M reference markers (M1 to M8) of the corresponding pattern (P1 to P3). ｐｏ partially occluded reference markers (M ｐｏ ) and N ｐｏ is a partially occluded fiducial marker (M ｐｏ ) and N ｐｏ >M-3, N in the M reference markers (M1 to M8) of the corresponding pattern (P1 to P3) ｐｏ partially occluded reference markers (M ｐｏ ) to detect the presence of Designed to be The surgical navigation system of claim 1 or 2, further configured to perform:

4. The data processor (DP) f １ ) N ｐｏ If ≦M−3, then the N ｐｏ partially occluded reference markers (M ｐｏ completing the image registration of the images (20) captured by the stereo camera (2) by removing f ２ ) N ｐｏ > In the case of M-3, N ｐｏ partially occluded reference markers (M ｐｏ stopping the surgical navigation if said presence of The surgical navigation system of claim 3 , further configured to perform:

5. 5. The surgical navigation system of claim 1, wherein each pattern (P1-P3) of the set generated in step b) is selected according to the positions of the M fiducial markers (M1-M8) relative to one another.

6. 6. The surgical navigation system of claim 1, wherein the set of patterns (P1-P3) generated in step b) satisfies a spread criterion that compares the relative position of the M fiducial markers (M1-M8) for each pattern (P1-P3) of the set from the position determined in step a), the spread criterion designed to detect a minimum spatial spread between the M fiducial markers (M1-M8) of a given pattern (P1-P3) of the set.

7. 7. The surgical navigation system of claim 1, wherein each pattern (P1-P3) of the set generated in step b) is selected according to the position of its corresponding M reference markers (M1-M8) relative to the stereo camera (2).

8. 8. The surgical navigation system of claim 1, wherein the set of patterns (P1-P3) generated in step b) satisfies a visibility criterion that compares the visibility levels of the M fiducial markers (M1-M8) among all patterns (P1-P3) of the set from the images (20) captured by a stereo camera (2), the visibility criterion being designed to find a minimum visibility level at which the M fiducial markers (M1-M8) of a given pattern (P1-P3) of the set can be distinguished by the stereo camera (2) within a predetermined margin of error.

9. The surgical navigation system of claim 8 in combination with claim 6, wherein the set of patterns (P1-P3) generated in step b) meets both the spread criterion and the visibility criterion.

10. The data processor (DP) b １ ) setting the integer number M of reference markers (M1 to M8) for each pattern (P1 to P3) of the set; b ２ ) browsing all or some of the combinations of M reference markers (M1-M8) from step a) to generate patterns (P1-P3); The surgical navigation system of any one of claims 1 to 9, configured to perform step b) by:

11. The data processor (DP) b ３ ) Step b ２ ) selecting a set of patterns (P1-P3) that satisfy said spread criterion from the patterns generated in 11. The surgical navigation system of claim 10 in combination with claim 6, configured to implement:

12. The data processor (DP) b' ３ ) Step b ２ ) selecting a set of patterns (P1-P3) that satisfy said visibility criterion from the patterns generated in 11. The surgical navigation system of claim 10 in combination with claim 8, configured to implement:

13. The data processor (DP) b” ３ ) Step b ２ selecting a set of patterns (P1-P3) that satisfy both said spread criterion and said visibility criterion from the patterns generated in 11. The surgical navigation system of claim 10 in combination with claim 9, configured to implement:

14. The surgical navigation system of any one of claims 1 to 13, wherein the criterion applied in step d) is a spread criterion.

15. The spread criterion is - if claim 14 is dependent on claim 1, the reference zone (Z) calculated in step c) for the set of patterns (P1 to P3) ｒｅｆ ) among the N reference markers (M1-M8) by detecting the minimum spatial spread between the poses of the at least one partially occluded reference marker (M ｐｏ detecting said presence of - if claim 14 is dependent on claim 2, the reference zone (Z ｒｅｆ ) and the reference zone (Z ｒｅｆ ) to find the minimum spatial extent between each pose of the at least one partially occluded reference marker (M 1 to M 8 ) among the N reference markers (M 1 to M 8 ). ｐｏ ) detecting the presence of 15. The surgical navigation system of claim 14, wherein the system is designed to:

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