Stereotaxic frame, device and method for synchronizing a robot, this stereotaxic frame and medical imaging

Abstract

TITLE OF THE INVENTION: STEREOTAX FRAME, DEVICE AND METHOD FOR REGISTERING BETWEEN A ROBOT, THIS STEREOTAX FRAME AND MEDICAL IMAGING The stereotaxic frame (30) for holding in position a part (58) of a predetermined patient's body comprises: - a rigid support piece (31) in the shape of a horseshoe or "U" which surrounds this part of the patient's body and has no element on one side of a plane passing through this part of the patient's body, this support piece being provided with cylindrical through openings (39), - cylindrical bars (32 to 35) which slide in the through openings of the support piece and have markers (43) identified in medical imaging, the cylindrical bars being transparent to the rays or electromagnetic field used for this imaging, - rods (36) for support on bones of this part of the patient's body, mounted on cylindrical bars,and - means for locking the support rods on the cylindrical bars. Figure for the abbreviation: Figure 8,

Description

Title of the invention: STEREOTAX FRAME, DEVICE AND METHOD FOR REGISTERING BETWEEN A ROBOT, THIS STEREOTAX FRAME AND MEDICAL IMAGING Technical field of the invention

[0001] The present invention relates to a stereotaxic frame, a device, and a method for registering a robot, this stereotaxic frame, and medical imaging. It is particularly applicable to the field of robot-assisted surgery and more specifically to the registration of an active or passive robotic arm, a stereotaxic frame, and medical imaging of a part of the patient's body to be operated on, for example, from a CT scan or an MRI (Magnetic Resonance Imaging) system. State of the art

[0002] The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section constitutes prior art simply because of its inclusion in this section.

[0003] Stereotaxy involves fixing a frame called a "stereotactic frame" to the skull. This frame is fixed by four pins after local anesthesia. Once the frame is in place, a medical imaging examination (MRI and / or CT scan) is performed. The stereotactic frame allows the exact position and volume of the tumor to be measured. The stereotactic frame remains in place until the operating room. The neurosurgeon also uses it during the procedure to navigate inside the brain. This stereotactic frame is a component, usually metallic, weighing approximately 800 g. Figure 1 shows a stereotactic frame 20 of a known type, alone, in a downward perspective. Figure 2 shows the stereotactic frame 20 illustrated in Figure 1 positioned on the head 21 of a patient, in a lateral perspective.This frame 20 consists of a rigid base 22, generally rectangular in shape, surmounted by four vertical pillars 23 to 26. Two of these pillars, 23 and 24, are positioned in front of the patient's face, opposite their forehead, and two others, 25 and 26, are positioned behind the head 21, at the level of the occiput. The function of these pillars 23 to 26 is to support screws 27 which, by tightening, secure the frame 20 to the patient's skull.

[0004] The stereotaxic frame is the essential factor in the stereotaxic concept. It is the indispensable element that ensures the geometric precision of this technique.

[0005] This frame is used to support and immobilize the head throughout the duration of neuroradiological examinations and surgical intervention, on the one hand, and to locate, with submillimeter precision, the position of the intracranial lesion to be treated, in the three directions of an orthonormal reference frame.

[0006] In the field of surgical robotics, stereotaxic frames make it possible to support and immobilize the patient's head and to perform the registration between the patient, the robot and the medical imaging. For this purpose, points of interest of the stereotaxic frame 20 are identified in the medical images, the frame which is then located by the robot, by vision (via a pointer equipped with a navigation reference carried by hand and a navigation camera which also locates a part of the robotic arm to determine the geometric correspondence between the medical imaging and the robot's reference frame) and / or by palpation (via a pointer carried by the robotic arm and manipulated in cooperative mode so that it reaches particular points, for example divots).

[0007] Although providing strong support, the shape of these stereotaxic frames, which completely surround the patient's head, does not allow for complete acquisition of the patient's facial surface by a 3D surface acquisition system, for example, a laser or structured light system. This limits the possibilities of non-contact registration, such as surface matching, during a surgical procedure.

[0008] Furthermore, the stereotaxic frame is located within the field of view of a medical image sensor, which generates imaging artifacts. These artifacts are sources of inaccuracies when tracking markers using automated tracking algorithms. Summary of the invention

[0009] The general concept of the invention consists of a C-, U-, or horseshoe-shaped stereotaxic frame that primarily serves to stabilize the patient's head while also enabling various types of registration, including non-contact surface matching, between a medical image of the area of ​​interest, for example, the patient's face, and a new three-dimensional image of the surface of that area of ​​interest captured by an image sensor. This stereotaxic frame frees up workspace for the surgeon.

[0010] In some embodiments, the frame materials are chosen to be radiolucent (for CT scans) and non-magnetic (for MRIs). Typically, these materials form a composite, for example based on carbon fibers and resin or PEEK-type plastic (first letters of the English word PolyEtherEtherKetone). Brief description of the figures

[0011] Other advantages, purposes and particular features of the invention will become apparent from the following non-limiting description of at least one particular embodiment of the device and method of the present invention, with reference to the accompanying drawings, in which: [Fig. 1] shows, in perspective, a stereotaxic frame from the previous art, alone. [Fig. 2] shows, in perspective, the frame illustrated in [Fig. 1] positioned on the head of a patient. [Fig.3] schematically represents, in front view, a first particular embodiment of the stereotaxic frame that is the subject of the invention, [Fig.4] schematically represents, in side view, the stereotaxic frame illustrated in [Fig.3], [Fig. 5] schematically represents, in top view, the stereotaxic frame illustrated in figures 3 and 4. [Fig. 6] shows, in side view, the placement of the stereotaxic frame illustrated in figures 3 to 5 in a robotic-assisted surgical operating room; [Fig. 7] shows, in side view, the performance of a non-contact registration before or during a robotic surgical procedure using the stereotaxic frame illustrated in figures 3 to 5. [Fig.8] shows, in cross-section, the field of view of a non-contact registration camera, [Fig.9] is an example of a point cloud resulting from a three-dimensional laser scan obtained by implementing the device that is the subject of the invention, [Fig. 10] is an example of a point cloud extracted from a medical image, [Fig. 1 1] represents, in the form of a flowchart, the steps of a particular embodiment of the registration process between a robot, a stereotaxic frame and medical imaging which is the subject of the invention, [Fig. 12] represents the positioning, using a probe, of a divot on a bar of the stereotaxic frame illustrated in figures 3 to 5, [Fig. 13] represents the positioning, using a navigation camera, of a divot on a bar of the stereotaxic frame illustrated in figures 3 to 5, [Fig. 14] schematically represents, in front view, a second particular embodiment of the stereotaxic frame that is the subject of the invention, [Fig. 15] schematically represents, in side view, the stereotaxic frame illustrated in [Fig. 14], and [Fig. 16] schematically represents, in top view, the stereotaxic frame illustrated in figures 14 and 15.

[0012] The present description is given by way of non-limiting grammar, each feature of an embodiment being able to be advantageously combined with any other feature of any other embodiment.

[0013] It should be noted from the outset that the figures are not to scale.

[0014] As will be understood from the present description, various inventive concepts can be implemented by one or more of the methods or devices described below, several examples of which are provided herein. The actions or steps carried out in the implementation of the method or device can be ordered in any appropriate manner. Consequently, it is possible to construct embodiments in which the actions or steps are performed in a different order than that illustrated, which may include the simultaneous execution of certain acts, even if they are presented as sequential acts in the illustrated embodiments.

[0015] The indefinite articles "un" and "une", as used in the description, should be understood as meaning "at least one", unless clearly stated otherwise.

[0016] The expression "and / or", as used in this document, shall be understood as meaning "either or both" of the elements thus joined, that is, elements that are present conjunctively in some cases and disjunctively in others. Multiple elements listed with "and / or" shall be interpreted in the same way, that is, "one or more" of the elements thus joined. Other elements may also be present, other than those specifically identified by the "and / or" clause, whether or not they are related to those specifically identified elements.Thus, by way of non-limiting example, a reference to "A and / or B", when used in conjunction with an open language such as "including", may refer, in one embodiment, to A only (possibly including elements other than B); in another embodiment, to B only (possibly including elements other than A); in yet another embodiment, to A and B (possibly including other elements); etc.

[0017] As used herein in the description, the term "or" should be understood inclusively.

[0018] As used in this description, the expression "at least one," with reference to a list of one or more elements, should be understood as meaning at least one element chosen from one or more elements in the list of elements, but not necessarily including at least one of each element specifically enumerated in the list of elements and not excluding any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than the elements specifically identified in the list of elements. to which the expression "at least one" refers, whether or not they are related to these specifically identified elements. Thus, by way of non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B", or, equivalently, "at least one of A and / or B") may refer, in one embodiment, to at least one, possibly including more than one, A, without B present (and possibly including elements other than B); in another embodiment, to at least one, possibly including more than one, B, without A present (and possibly including elements other than A); in yet another embodiment, to at least one, possibly including more than one, A, and at least one, possibly including more than one, B (and possibly including other elements); etc.

[0019] In the description below, all transitive expressions such as "comprising", "including", "carrying", "having", "containing", "implying", "holding", "composed of", and others, should be understood as open, that is, as meaning including but not limited to. Only the transitive expressions "consisting of" and "consisting essentially of" should be understood as closed or semi-closed transitive expressions, respectively.

[0020] Throughout this description, the terms "upper" and "top" refer to what is at the top when the device of the present invention is in its operational configuration. The terms "lower" and "bottom" refer to what is at the bottom when the device of the present invention is in its operational configuration. The term "inside" refers to what is inside the device. The term "outside" refers to what is outside the device.

[0021] A stereotaxic frame of the invention is defined for a model patient, for example, a user 1.78 m tall and weighing 77 kg. Of course, the same stereotaxic frame can be used for a group of patients whose morphological characteristics are similar to those of the model. A person skilled in the art who designs a stereotaxic frame of the invention knows how to determine the dimensions of the bones of the patient's body, and in particular those of the area of ​​interest, for example, the patient's skull, based on the predetermined patient for whom the stereotaxic frame is intended. Indeed, this anthropometric data is well documented.

[0022] The implementation of the invention therefore involves the production of a range of stereotaxic frames covering a large part of the morphologies of patients, for example a single stereotaxic frame to cover the morphologies of 70% of the European population and two frames can cover 90% of the European population.

[0023] Figures 1 and 2 have already been described.

[0024] Figures 3 to 5 show a first particular embodiment of the stereotaxic frame of the invention, respectively in front view, side view and top view.

[0025] The stereotaxic frame 30 includes a rigid support piece 31 having a general horseshoe or "U" shape, which supports cylindrical fixing and repositioning bars 32 to 35. In geometric terms, a horseshoe shape is a shape delimited by two segments of ellipses covering, for at least one of these ellipses, at least the ends of the minor axis, without covering one of the ends of the major axis nor more than three-quarters (preferably, two-thirds and, even more preferably, three-fifths) of the perimeter of each of these ellipses.

[0026] The stereotaxic frame 30 thus does not include any element on one side of a plane passing from a predetermined plane through a predetermined area of ​​interest of the patient's body. For example, when the stereotaxic frame is intended to hold the patient's head (for example, for intracranial surgery), the predetermined area of ​​interest may be the patient's face, and the predetermined plane may pass through the patient's chin and cheekbones, temples, or eyes. According to another example, when the stereotaxic frame is intended to hold the patient's knee, the predetermined plane may be the principal plane of the patella passing through the center of gravity and the principal axes of inertia of the patella exhibiting the two maximum principal moments of inertia, or the cross-sectional plane of the patella for which the cross-sectional area is maximal. In the embodiment illustrated in [Fig.[Fig. 3] to [Fig. 5], the support piece 31 is delimited by two parallel planes (right and left in [Fig. 4] and top and bottom in [Fig. 5]), by two elliptical segments (visible in [Fig. 3]), and by two bevels (top in [Fig. 3]). The frame 30 exhibits symmetry with respect to two orthogonal planes. The bars 32 to 35 are cylindrical, meaning they have a ruled surface whose generatrices are parallel. A section along a plane perpendicular to these generatrices is called a directrix. In the embodiment illustrated in Figures 3 to 5, this directrix is ​​a rectangle. The bars 32 to 35 are inserted by sliding into the support piece 31 via cylindrical through openings (or "lights") 39 whose directions correspond, within clearance, to those of the bars 32 to 35. The axes of the through openings 39 formed in the support piece 31 are preferably perpendicular to the general plane of the support piece 31.

[0027] Threaded rods 36 ending in points 37 pass through tapped holes (not shown) formed in bars 32 to 35, tapped holes whose thread pitch corresponds to that of the threaded rods 36. The axis of these tapped holes, and therefore the threaded rods 36, are preferably perpendicular to the main axis of bars 32 to 35, that is to say in a plane parallel to the general plane of the support part 31.

[0028] An arm 38 supports the support piece 31.

[0029] In the embodiment shown in Figures 3 to 5, a positioning arm 40 supports a navigation reference 41 in a fixed manner relative to the frame 30, that is- that is to say, without any freedom of movement of the reference 41 relative to the frame 30. A navigation reference is a set of at least four markers pre-mounted on a rigid support, in non-coplanar and asymmetrical positions. An image of this navigation reference thus makes it possible to identify the position (three coordinates in an orthonormal coordinate system) and the orientation (three angular coordinates in this system) of this navigation reference. Preferably, the arm 40 and the reference 41 remain permanently attached to the frame 30.

[0030] Preferably, and as can be seen in [Fig. 5], at least one bar 32 to 35

[0031] is equipped, within its volume, with an asymmetric network of markers 43 intended for the Alignment between the patient's head and the surgical robot's geometric reference frame, as described later. For example, each bar 32 to 35, and preferably also the support piece 30, are made of composite material (radiolucent and / or non-magnetic depending on the type of medical imaging used) with markers 43 embedded directly into the material for each bar 32 to 35. The markers 43 simply need to be identifiable in medical imaging. These markers 43 differ depending on the type of imaging used (for example, stainless steel beads for CT scans and beads containing a specific visible liquid for MRIs).

[0032] Preferably, each bar 32 to 35 is provided, within its volume, with an asymmetric array of markers 43, the arrays of the different bars 32 to 35 being sufficiently different for these bars to be identified by medical imaging processing. Furthermore, the asymmetry of each array of markers 43 is sufficient for the position and orientation of each bar 32 to 35 to be determined by medical imaging processing.

[0033] The rigidity of the fixing of the bars 32 to 35 in the support piece 31 is ensured by the insertion of the supports 37 against the patient's head, through the mechanical effect of angular constraint. Alternatively or complementaryly, a means is provided for locking the position of each of the bars 32 to 35 in the support piece 31, for example a threaded rod that passes through a tapped hole in the support piece 31, and, once the bar is positioned in the support piece 31, presses against this bar.

[0034] [Fig.6] represents, in side view, the placement of the stereotaxic frame 30 during a surgical intervention with robotic assistance.

[0035] In [Fig. 6], a robot 50 is shown comprising a trolley 51 equipped with wheels 52 and carrying a robotic arm 54 with joints 55. The trolley also includes a computing, processing, and control unit 53 which performs, in particular, possibly in cooperation with an external computer system such as a web-accessible server, the geometric alignment between the geometric reference frames of the carriage 52, the stereotaxic frame 30 and a medical image stored in memory.

[0036] A patient 57 is lying on a surgical table 59. The head 58 of the patient 57 is fixed to the stereotaxic frame 30. This frame 30 is supported by an arm 56, for example telescopic, which terminates in an attachment point 61 of the frame 30 to the arm 38. This attachment point 61, for example a ball joint, allows several degrees of freedom of the frame 30 relative to the arm 38, in a known manner. Preferably, at least the end of the arm 56 is radiolucent, in order to be able to obtain medical images during the procedure to check / verify the placement of implants, for example (typically electrodes for brain surgery).

[0037] A navigation reference 60, similar to reference 41, is attached to the patient's head 57.

[0038] The navigation reference 60 makes it possible to detect if the patient's head 57 moves relative to the stereotaxic frame 30 during the surgical procedure, for example, due to a seizure. In this case, either a new registration is performed or the registration is updated taking into account the displacement data from the patient's head navigation reference, thus avoiding the need to perform a new registration.

[0039] Furthermore, in the case where an intraoperative control MRI is performed during surgery, monitoring the movements of the patient's head relative to the frame allows the procedure to continue, after the control MRI, without re-registering, if there is no change in position between the patient reference and the frame reference.

[0040] [Fig.7] represents, in side view, the realization of a non-contact alignment between the robot 50, stereotaxic frame 30 and medical imaging stored in memory, for example in the memory of the computing, processing and control unit 53, upstream or during a robotic surgical procedure or during a surgical procedure.

[0041] The robotic arm 54 supports, at its free end, a non-contact registration unit 62. This unit 62 includes an optical means enabling 3D modeling of the surface of the area of ​​interest (here all or part of the head 58 of the patient 57), for example a structured light type 3D camera.

[0042] In the embodiment shown in [Fig.7], the registration unit 62 includes a means 63 for projecting a laser line 64 formed on the surgical intervention area on the patient 57, here the head 58 of the patient 57. The registration unit 62 also includes a means for projecting a laser point (not shown), also called a laser pointer, configured to measure a distance, in a known manner.

[0043] The registration unit 62 is also equipped with a distance sensor 68 for the points of the laser line 64 and a handle 67 with which an operator 66 can manipulate this unit 62. The distance sensor 68 includes, for example, an image sensor and a means for measuring distance by triangulation, according to known techniques.

[0044] The registration unit 62 can be installed by the operator 66 at the free end of the arm 54 as a "tool." Alternatively, the registration unit 62 is integrated into this end of the arm 54. The advantage of integration is that it avoids having to remove and replace the registration unit 62 during a surgical procedure, in case the registration is lost during the procedure. This integration also prevents assembly errors by the operator 66 when installing the registration unit 62 at the end of the arm 54, as these assembly errors could lead to registration inaccuracies. The arrow 69 represents the direction in which the laser line 64 scans the user's head.

[0045] [Fig-8] shows, in front view, the implementation of a non-contact registration showing The absence of masking disruption to the patient's face and skull by elements of the prior art stereotaxic frame. The projection angle of the laser line projection means 63 is represented by its extreme beams 65.

[0046] [Fig.9] is an example of a point cloud 70 of 71 obtained from a three-dimensional laser scan dimensions obtained by implementing the device that is the subject of the invention. The point cloud 70 of points 71 is produced from a three-dimensional surface extraction captured by the registration unit 62, by implementing the projection of a laser line 64 and the distance sensor 68. Each point 71 of this point cloud 70 is located according to a geometric coordinate system linked to the conditions of the three-dimensional image capture and therefore to the position of the robot 50.

[0047] [Fig. 10] is an example of a point cloud 75 of points 76 extracted from a medical image. Each point 76 of this cloud 75 is located according to a geometric coordinate system linked to the conditions under which the medical image was acquired. In addition, each marker 43 of one of the bars 32 to 35 is located according to this geometric coordinate system. For the sake of clarity in [Fig. 9], only two markers 43 are shown there.

[0048] In order for the robot 50 to virtually position the medical image 75 in space relative to the actual space of the patient 57, a matching operation (also called "registration") of the point clouds 70 and 75 71 and 76 is necessary. The medical image 75 is thus located in the geometric coordinate system of the robot 50. In this way, the markers 43 of the bars 32 to 35 of the stereotaxic frame 30 are located in the medical image, that is to say, their geometric coordinates relative to the head 58 of the patient 57 are known.

[0049] The implementation of the registration between the robot, the stereotaxic frame 30 and a medical imaging providing the point cloud 75 76 follows the steps of the process 80 illustrated in [Fig. 11].

[0050] It should be noted that surface matching is sufficient for this registration. The positions of the markers 43 are therefore not necessary for this registration. The frame 30 thus allows for multimodal registration. That is to say, it allows several registration methods and the ability to switch from one type of registration to another depending on the progress and needs of the surgery (particularly in terms of precision). For example, medical imaging is performed before the procedure using the frame 30. The network of markers 43 is identified in the image. Knowing the network of markers 43, it can be linked to the geometry of the frame (by design). Then, specific points of the frame (known by design) are located in real space, either with the robot equipped with a pointer at the end of its arm (see [Fig. 12]), or directly with a manual pointer equipped with a navigation reference (see [Fig. 13]).This allows for a link to be established between the geometry of frame 30 in medical imaging space and the geometry of frame 30 in real space. During surgery, if the registration is lost, for example because the head 58 of patient 57 has moved relative to frame 30, the markers 43 in the medical imaging can no longer be used to perform a new registration, as the geometric relationship between frame 30 and the head 58 of patient 57 is no longer the same. With the frame that is the subject of the invention, the surgeon avoids having to recreate a medical image, which has serious drawbacks, including exposing the patient to additional radiation and increasing the preparation time for the medical imaging. Instead, the surgeon performs a surface registration of the area of ​​interest, using the surface data from the initial medical imaging to obtain a new registration.

[0051] It is therefore generally sufficient to obtain the three-dimensional coordinates of the points of the head in the geometric reference frame of the robot 50, in order to obtain, by surface matching, the transformation matrix of the coordinates in the reference frame of the medical imaging into coordinates in the geometric reference frame of the robot 50.

[0052] This is the object of method 80 illustrated in [Fig. 11], in an embodiment employing a surface scanner with laser line projection onto the area of ​​interest. In other embodiments, another type of optical means enabling 3D modeling of the surface of the area of ​​interest, for example a structured-light 3D camera, is used. In these other embodiments, steps 86 to 89 described below are replaced by steps for obtaining a 3D model of the surface of the area of ​​interest, steps known to those skilled in the art.

[0053] In the process 80, during a step 81, the patient 57 is positioned on the operating table 59 as illustrated in [Fig. 6]. The robot 50, and in particular the trolley 51, is placed opposite the area of ​​interest, i.e., the surgical intervention area on the head 58 of the patient 57. The trolley 51 does not move after the step 81, until the end of the surgical procedure. Preferably, the trolley 51 is equipped with jack feet (not shown) which are deployed during step 81 to prevent any movement of the trolley 51. At the end of step 81, the robot 50 is started, and in particular its robotic arm 54.

[0054] During a step 82, the robotic arm 54 performs an automatic prepositioning so that its free end is near the area of ​​interest, in a position where the operator 66 can easily install the registration unit 62 if it is not integrated into the arm 54. During this step 82, the robotic arm 54 moves from a so-called "storage" position, in which it is folded above the carriage 51, to a deployed position allowing easy installation of the registration unit 62 on the free end of the arm 54. If the unit 62 is integrated into the arm 54, the position reached by the arm 54 is a position allowing the operator 66 to grasp the handle 67 to move it, in cooperative mode, to the area of ​​interest to be scanned.

[0055] During a step 83, in the event that the recalibration unit 62 is not integrated into the arm 54, it is installed at the free end of the robotic arm 54.

[0056] During a step 84, the operator 66 roughly positions the non-contact registration unit 62 parallel to the area of ​​interest, using the handle 67 of the registration unit 62 and the cooperative mode of the robotic arm 54. Alternatively, this rough positioning is carried out automatically by the robotic arm 54.

[0057] The cooperative mode is implemented by means of at least one force sensor located at the end of the robotic arm 54, or directly in the joints 55 of the robotic arm 54, if it is an "active" arm. In this cooperative mode, the arm 54 can apply constraints to the movements of its extremity. For example, the only movements permitted, in cooperative mode, at the free end of the robotic arm 54 are in a plane roughly parallel to the area of ​​interest or along a straight line roughly parallel to an axis of symmetry of the area of ​​interest, for example, the face of the patient 57. Alternatively, the plane is parallel to the upper surface of the operating table 59 and / or the axis is parallel to the longitudinal axis of the operating table 59.

[0058] During step 85, the laser pointer 68 provides a distance between the registration unit 62 and the area of ​​interest. Based on this initially measured distance, the distance is adjusted by moving the registration unit 62, either automatically or manually. This adjustment is made taking into account that a distance that is too small can cause difficulties in terms of the distance measurement area covered by the registration unit 62 and in terms of the sterility of the operating field. Conversely, a distance that is too large increases the uncertainty in distance measurements. Typically, the adjusted distance is on the order of 40 centimeters.

[0059] This is the configuration illustrated in [Fig. 7]. During a step 86, the projection angle of the planar laser beam is adjusted, which provides a light line 64 on the patient's skin in the area of ​​interest. The length of the laser beam line 64 is adjusted via a user interface (not shown), for example, a touchscreen mounted on a different carriage of the robot 50 than the carriage 51. This dimension of the light line 64 on the scanned surface is thus adjusted to avoid illuminating elements external to the patient, for example, the stereotaxic frame 30, as illustrated in [Fig. 8]. Alternatively, the laser pointer 68 is used to define the edges of the projection field to be covered by the light line 64 projected onto the patient's head 58.

[0060] During a step 87, the laser registration unit 62 is operated and the coordinates of the starting position of the scanning of the area of ​​interest with the laser light line 64 are recorded in the robot's geometric frame of reference, by means of a control button (not shown) on the handle of the registration unit 62 or the user interface.

[0061] During a step 88, the robotic arm 54 switches to cooperative mode under axial or planar constraint parallel to the area of ​​interest.

[0062] During a step 89, the operator 66 moves the robotic arm 54 under axial or planar constraint parallel to the area of ​​interest in order to carry out the scanning of this area of ​​interest and the measurement of the distance to the registration unit 62 of each point illuminated by the light line 64.

[0063] During a step 90, the computing unit 53 performs a point cloud extraction (3D surface similar to the point cloud 70 71) as output data from the laser scan. It is noted that this three-dimensional output data from the laser scan can be used in so-called "open" surgery, i.e., by exposing the bony part of the area concerned in the patient's body to the air (for example, part of the spine, a knee, or a hip) without "intraoperative" (during the operation) imaging, but with "preoperative" (pre-op) imaging.

[0064] During a step 91, the computing unit 53 performs an extraction of a point cloud from the medical imaging, similar to the point cloud 75 of 76.

[0065] During a step 92, the computing unit 53 uses a point cloud matching algorithm, for example of the ICP (Iterative Closest Point) type, to calculate the transformation matrix between the real-space reference frame of the area of ​​interest (in the geometric coordinates of the robot 50) and the reference frame of the associated medical imaging. This makes the point clouds coincide in the robot's geometric coordinate system, minimizing the error between these two clouds. Preferably, before using this algorithm, the operator performs a quick "manual" coarse registration step. This step allows to accelerate the convergence of the automatic ICP algorithm. To this end, the operator identifies equivalent anatomical areas (or points) within the point clouds of the laser scan and medical imaging. A first, so-called "coarse" registration is then performed on this basis. The ICP algorithm uses this coarse registration as input data.

[0066] Preferably, a confidence index is assigned to the match finally obtained, for example by measuring an average distance between matched points, and, if the confidence index is too low (for example, this average distance is greater than a predetermined limit), steps 85 to 91 are performed again. Two examples of confidence indices are described below: 1. An overall average RMS (root mean square error) index is calculated for the entire data cloud. The resulting RMS value (e.g., 0.26 mm) is displayed on the user interface using a two-color code (green acceptable, red unacceptable). If the index is green, operator 66 can continue the procedure. A red index on the user interface requires operator 66 to perform another surface laser scan. 2. A point index (distance between two points matched between the two point clouds) which can be represented as a color map directly on the 3D extraction of the medical image or on the 3D surface obtained via laser scanning. If the percentage of points farther apart than a predetermined limit distance (e.g., one millimeter) exceeds a limit value (e.g., 10%), or if a distance between corresponding points exceeds another predetermined limit distance (e.g., three millimeters), a red index on the user interface requires the operator to perform a new surface laser scan.

[0067] During a step 93, the computing unit 53 creates a no-go zone for the robotic arm 54 and its instrument holder from the scanned 3D surface and / or the 3D reconstruction of the medical imaging registered with the laser-scanned 3D surface. This no-go zone prohibits collisions between the robotic arm 54 and the patient's body 57 at least in the area of ​​interest (the entire volume of the head 58, in the case shown in Figures 6 and 7).

[0068] Thanks to the geometric positioning of the registration unit 62, performed by a navigation camera (preferably on a different trolley than the trolley 51) via a navigation reference, the coordinates of the points in the area of ​​interest within the operating room space can be obtained. Once a robotic arm 54 is in place, its free end is, in turn, located within this space, for example by implementing at least one other navigation reference. To this end, registration between the robotic arm and the navigation camera must be performed as follows. A navigation reference is positioned at the free end. of the robotic arm 54, either as a tool to be carried or integrated at this end of the arm 54. The robotic arm 54 then moves automatically to different known positions in space. These different positions are recorded by the navigation camera and located in its geometric reference frame. The positions seen by the navigation camera can then be linked to the positions of the joints (via the joint encoders) of the robotic arm 54. Alternatively, to avoid the time required to assemble the navigation reference (which can lead to incorrect assembly and therefore inaccuracies) and to move the arm 54 to different positions, a navigation reference can be permanently mounted on the carriage 521 of the robotic arm 54.Knowing, by design, the location of this reference relative to the base of the robotic arm (and therefore to its reference frame), the navigation camera will only have to locate this reference in order to perform the matching with the reference frame of the robotic arm 54. The coordinates of the points of the area of ​​interest, in three dimensions, can then be matched with the coordinates of the robotic arm 54 and with the medical imagery previously stored.

[0069] Alternatively, specific points on the robot base, the robot itself, and / or the tools it carries are located using a pointer equipped with a navigation reference. Thus, divots are used on a wider selection of points known by design, and they are located with a navigation pointer.

[0070] To locate each bar 32 to 35 in the space of the robot 50 (i.e., in its geometric reference frame), one option is to locate at least one divot 100 formed on this bar with a mechanical probe 101 mounted on the arm 54, as illustrated in [Fig. 12]. The shape of the head (or free end) 102 of the probe 101 corresponds to the shape of the divot 100, which is generally spherical or conical. The arm 54 then operates in cooperative mode, its movements being controlled by an operator. When the sensors (not shown) of the probe 101 determine that the head 102 of the probe 101 is touching the bottom of the divot 100, the acquisition of the coordinates is validated via a confirmation button in the user interface, and the robot memorizes its geometric position and, consequently, the position of the bar 32 to 35.

[0071] A second option, represented in [Fig. 13], consists of implementing a navigation reference 105 whose end is inserted into the bottom of the divot 100. In this case, the navigation camera locates the position of the navigation reference 105 in its geometric reference frame and, consequently, the position of its end inserted into the bottom of the divot 100. The correspondence between the geometric reference frame of the robot 50 and the geometric reference frame of the navigation camera having already been determined, the robot obtains the position of the bar 32 to 35 in its own geometric reference frame.

[0072] Although, in the embodiments described above, the distance sensor 68 is mounted on the robotic arm 54, in other embodiments, this distance sensor is mounted on a different carriage than the robotic arm 54. Of course, the geometric reference frame of this distance sensor is then fixed and the coordinate transformation matrix in this reference frame into coordinates in the reference frame of the robot 50 is then predetermined.

[0073] The stereotaxic frame 30 is thus used both to support and immobilize the head 58 of the patient 57 during the entire duration of the neuroradiological examinations and the treatment itself, and to locate with submillimeter precision the position of the intracranial lesion to be treated in the three planes of space.

[0074] Figures 14 to 16 show a second particular embodiment of the stereotaxic frame of the invention, respectively in front view, side view and top view.

[0075] The stereotaxic frame 130 has a general horseshoe shape, which supports rods 136, preferably threaded. In the embodiment illustrated in [Fig. 14] to 16, the frame is delimited by two parallel planes (right and left in [Fig. 15] and top and bottom in [Fig. 16]), by two ellipses (visible in [Fig. 14]) and by two bevels (top in [Fig. 14]). The frame 130 exhibits symmetry with respect to two orthogonal planes (except for the markers described below that it incorporates).

[0076] The threaded rods 136 terminate, on the inner side of the frame 130, in points 137. Threaded rods 136 pass through through openings 139, preferably tapped (not shown) formed in the frame 130. The threads of the through openings 139 have a thread pitch corresponding to that of the threaded rods 136. These threads, and therefore the threaded rods 136, are preferably perpendicular to the plane tangent to the outer surface of the frame 130 and therefore in a plane parallel to the general plane of the frame 130. In variants, other types of mechanical means for locking the rods 136 in the through openings 139 are implemented.

[0077] An arm 138 supports the frame 130. In the embodiment shown in figures 14 to 16, a positioning arm 140 supports a navigation reference 141 in a fixed manner relative to the frame 130, i.e. without any freedom of movement of the reference 141 relative to the frame 130. Preferably, the arm 140 and the reference 141 remain permanently linked to the frame 130.

[0078] Preferably, and as can be seen in figures 14 to 16, the frame 130 is provided, in its volume, with an asymmetric network of markers 142 intended for re-alignment between the patient's head in the geometric reference frame of the surgical robot.

[0079] For example, the frame 130 is made of composite material (radio-transparent and / or non-magnetic) with markers 142 inserted directly into the material.

[0080] In other embodiments of the stereotaxic frame of the invention, the support piece of the stereotaxic frame according to the first embodiment comprises markers 143 as shown for the second embodiment. These markers 143 allow for the geometric identification of the position and orientation of this support piece, in addition to the geometric identification of the position and orientation of each cylindrical bar 32 to 35 with the markers 43. Presentation of the invention

[0081] The present invention aims to remedy all or part of the drawbacks of the prior art.

[0082] To this end, the present invention relates to a stereotaxic frame for maintaining in position a part of the body of a predetermined patient, which comprises: - a rigid support piece in the shape of a horseshoe or "U" configured to surround this part of the patient's body and having no elements on one side of a predetermined plane passing through this part of the patient's body, this support piece being provided with cylindrical through openings, - cylindrical bars configured to slide in through-holes in the support piece and having markers configured to be located in medical imaging using beams or an electromagnetic field, the cylindrical bars being, at least partially, transparent to said beams or electromagnetic field, - support rods on bones in this part of the patient's body, mounted on cylindrical bars, and - means of locking the support rods on the cylindrical bars.

[0083] Thanks to these arrangements, the part of the user's body on which the surgical intervention takes place remains visible beyond the plane passing through this part of the body, which allows image captures of this part of the body and, thanks to these image captures, geometric matching (also called "registration") of the medical imaging, the stereotaxic frame and a navigation robot.

[0084] In some embodiments, the cylindrical bars are made of radio-transparent material and the markers are metallic balls.

[0085] Thus, medical imaging performed by scanners can allow the precise geometric localization of each bar while limiting the artifacts related to the presence of these bars.

[0086] In some embodiments, the cylindrical bars are made of non-magnetic material and the markers are balls containing a non-magnetic material.

[0087] Thus, magnetic resonance medical imaging can allow the precise geometric localization of each bar while limiting the artifacts related to the presence of these bars.

[0088] In embodiments, the markers of each cylindrical bar form an asymmetric geometric network of markers configured so that the position and orientation of each bar can be determined by medical imaging processing.

[0089] In some embodiments, the geometric networks of markers of the different bars are different and configured so that these bars can be identified by processing a medical image.

[0090] In embodiments, the patient's body part is the patient's head, the rigid horseshoe-shaped or "U"-shaped support piece being configured to surround this patient's head and not having any element on one side of a plane passing through the patient's chin and cheekbones, temples or eyes.

[0091] Thus, an image of the patient's face can be produced, before or during the surgical procedure, without the support piece obscuring the essential elements (in particular the chin, mouth, nose and eyes) which allow for precise geometric positioning of the patient's head.

[0092] In embodiments, the stereotaxic frame includes a fixed navigation reference relative to the support piece.

[0093] This navigation reference allows, continuously, the precise geometric positioning of the position and orientation of the stereotaxic frame by a navigation camera.

[0094] In embodiments, the support piece has a plane of symmetry whose section with the support piece has the shape of a horseshoe or a "U", the axes of the through openings formed in the support piece are perpendicular to the general plane of the support piece and the axes of the support rods are parallel to the general plane of the support piece.

[0095] In embodiments, at least one cylindrical bar includes a divot.

[0096] This divot allows, for example with a navigation reference or a probe, the precise geometric positioning of the cylindrical bar.

[0097] In embodiments, the support piece includes markers configured to be located in medical imaging using rays or an electromagnetic field, the support piece being, at least partially, transparent to said rays or electromagnetic field.

[0098] These complementary markers allow for the precise geometric localization of the support piece in medical imaging, while limiting artifacts related to the presence of this support piece.

Claims

Demands

1. Stereotaxic frame (30) for maintaining in position a predetermined part (58) of a patient's (57) body, characterized in that it comprises: - a rigid support piece (31) in the shape of a horseshoe or "U" configured to surround this part of the patient's body and not having any element on one side of a predetermined plane passing through this part of the patient's body, this support piece being provided with cylindrical through-holes (39), - cylindrical bars (32 to 35) configured to slide in the through-holes of the support piece and having markers (43) configured to be located in medical imaging using rays or an electromagnetic field, the cylindrical bars being, at least partially, transparent to said rays or electromagnetic field, - rods (36) for bearing on bones of this part of the patient's body, mounted on the cylindrical bars,and - means for locking the support rods onto the cylindrical bars.

2. Stereotaxic frame (30) according to claim 1, wherein the cylindrical bars (32 to 35) are made of radio-transparent material and the markers (43) are metallic balls.

3. Stereotaxic frame (30) according to claim 1, wherein the cylindrical bars (32 to 35) are made of non-magnetic material and the markers (43) are balls containing a non-magnetic material.

4. Stereotaxic frame (30) according to any one of claims 1 to 3, wherein the markers (43) of each cylindrical bar (32 to 35) form an asymmetric geometric array of markers (43) configured so that the position and orientation of each bar can be determined by medical imaging processing.

5. Stereotaxic frame (30) according to claim 4, wherein the geometric marker arrays (43) of the different bars (32 to 35) are different and configured so that these bars can be identified by processing medical imaging.

6. Stereotaxic frame (30) according to any one of claims 1 to 5, wherein part (58) of the patient's body (57) is the patient's head, the rigid support piece (31) in the shape of a horseshoe or "U" being configured to surround the patient's head and not having any element on one side of a plane passing through the patient's chin and cheekbones, temples or eyes.

7. Stereotaxic frame (30) according to any one of claims 1 to 6, which includes a navigation reference (41) fixed relative to the support piece (31).

8. Stereotaxic frame (30) according to any one of claims 1 to 7, wherein the support piece (31) has a plane of symmetry whose section with the support piece has the shape of a horseshoe or a "U", the axes of the through openings (39) formed in the support piece (31) are perpendicular to the general plane of the support piece (31) and the axes of the support rods (36) are parallel to the general plane of the support piece.

9. Stereotaxic frame (30) according to any one of claims 1 to 8, wherein at least one cylindrical bar (32 to 35) has a divot (100).

10. Stereotaxic frame (30) according to any one of claims 1 to 9, wherein the support piece (31) has markers (143) configured to be located in medical imaging using beams or an electromagnetic field, the support piece being, at least partially, transparent to said beams or electromagnetic field.

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