Surgical robotic system and method for defining limited access volume of such surgical robotic system

Abstract

The present invention relates to a method for determining a limited access volume of a surgical robotic system comprising a robotic arm and an end effector, a registration phantom comprising a set of radiopaque references, the registration phantom located near a region of interest, the method comprises the steps of: acquiring, by an imaging system, at least one 2D X-ray image comprising a set of references of a region of interest and a registration phantom; defining a phantom coordinate system attached to the registration phantom using the acquired at least one 2D X-ray image; determining the attitude of the phantom coordinate system in the selected coordinate system; the restricted access volume is defined in the selected coordinate system to include the region of interest, an envelope of the restricted access volume being calculated based on the determined pose of the phantom coordinate system in the selected coordinate system. The invention also relates to a system implementing the method for treating a region of interest of a patient's body.

Description

Technical Field

[0001] The present invention relates to a surgical robot system and a method for defining the restricted access volume of such surgical robot system. Background Technology

[0002] Surgical robotic systems are being used more and more to assist users (e.g., surgeons) during surgical interventions.

[0003] For example, in spinal surgery, a user may need to have one or more screws implanted in at least one vertebra. A robotic arm can assist the user by holding a drill guide and keeping it aligned with a planned axis. The user can then use a hand drill to drill holes in the vertebra along the planned axis through the drill guide held by the robotic arm to receive the screws.

[0004] In this regard, the use of a positioning system that can locate the tracker in real time (high frequency, low latency) can be used to perform such manipulations with the assistance of a surgeon or autonomously. Both anatomical structures and surgical instruments can be located, which allows for the determination of the relative position of the surgical instruments with respect to the anatomical structure to be treated in real time.

[0005] For this purpose, surgical tools and anatomical structures can include trackers rigidly attached to them, each tracker being tracked by a positioning system.

[0006] In some cases, the tracker can be rigidly attached to a part of the surgical robot system rather than directly to the surgical tool, thus allowing indirect tool positioning based on knowledge of the kinematic model of the surgical robot system between the tracker and the tool at any given time.

[0007] However, the autonomous manipulation of surgical instruments used to treat anatomical structures via robotic systems comes with significant safety concerns. In reality, after planning the trajectory of the surgical instrument, the surgeon does not directly execute the planned surgical procedure. Furthermore, the tracker attached to the anatomical structure can move, for example, due to unintentional impacts or pushes applied to it. Alternatively, the tracker attached to the surgical instrument may deviate from its calibration. Or any software error may lead to geometrical errors, causing the autonomous robot to position itself incorrectly while executing its planned trajectory. Similarly, the tracker may be defective for various reasons (blood splattering on it in the case of optical tracking, electromagnetic interference in the case of electromagnetic tracking), leading to incorrect tracking.

[0008] Therefore, it is important to enhance the safety of robot-assisted or robotic surgical procedures by being able to limit the configuration of the surgical system to a prohibited volume that it will never enter.

[0009] Document WO2018081136 discloses a method for defining such a forbidden volume. In this paper, the patient's skin surface is identified in an image dataset of the patient's anatomy to generate a boundary surface. The image dataset and the boundary surface are then registered in a common coordinate system to define the forbidden volume. However, this method is not applicable to all imaging systems, particularly X-ray cone-beam computed tomography (CBCT). In fact, it is more difficult to identify the patient's skin surface using X-ray images acquired using a CBCT imaging system because, due to the CBCT technique, the grayscale values ​​of the pixels associated with the patient's skin will have greater variation between each X-ray image compared to images acquired using other X-ray imaging systems.

[0010] Another solution uses a camera mounted on the end of a robotic arm to visually scan the patient's skin to define the restricted volume. However, this method requires additional steps and materials.

[0011] The purpose of this invention is to provide a simple solution that requires no additional steps or materials and is applicable to any X-ray imaging system. Summary of the Invention

[0012] According to a first aspect, the present invention relates to a method for determining a restricted access volume of a surgical robotic system, the surgical robotic system including a robotic arm and an end effector adapted to treat a region of interest in a patient's body, the registration phantom including a set of radiopaque references located near the region of interest, the method comprising:

[0013] - Acquire at least one 2D X-ray image of the set of references containing the region of interest and the registration phantom using an imaging system;

[0014] - Use at least one acquired 2D X-ray image to define the phantom coordinate system attached to the registered phantom;

[0015] - Determine the orientation of the phantom coordinate system in the selected coordinate system;

[0016] - Define the restricted access volume in the selected coordinate system to include the region of interest, and calculate the envelope of the restricted access volume based on the determined pose of the phantom coordinate system in the selected coordinate system.

[0017] Some preferred but non-limiting features of the above method are as follows, which may be used alone or in any technically feasible combination:

[0018] - The phantom coordinate system is defined by a first axis, a second axis, and a third axis, and the method includes:

[0019] - Define the first axis as the axis of rotation of the X-ray imaging system (300);

[0020] - Use the at least one 2D X-ray image to define the intermediate axis;

[0021] - Determine the second axis using the first axis and the intermediate axis;

[0022] - A third axis is determined using the first axis and the second axis to generate the phantom coordinate system defined by the first axis, the second axis, and the third axis.

[0023] -Defining the intermediate axis includes:

[0024] - Use at least one 2D X-ray image acquired to determine the location of each reference;

[0025] - The principal plane of the registration phantom is determined using the position of each determined datum and the known relationship between the datum and the geometry of the registration phantom;

[0026] - Define the intermediate axis as the normal vector of the principal plane of the registration phantom.

[0027] - The envelope of the restricted access volume is calculated to include at least a portion of the principal plane of the registration phantom.

[0028] - The steps to limit restricted access volume include:

[0029] - Identify the highest point of the registered phantom in the phantom coordinate system along the third axis;

[0030] - Calculate the envelope of the restricted access volume to include at least a portion of the restrictive plane, the restrictive plane including the identified highest point of the registered phantom and having a normal vector according to the third axis of the phantom coordinate system.

[0031] - The highest point of the registration phantom can be the reference or a specific part of the registration phantom, such as the corner of the registration phantom.

[0032] - At least one dimension of the operating table where the patient's body is located and / or at least one dimension of the patient's body are further used to calculate the envelope of the restricted access volume.

[0033] - The size and shape of the restricted access volume can be further manually adjusted by the user.

[0034] -The restricted access volume includes at least:

[0035] - The first subvolume, into which the surgical robot system may occasionally enter under specific conditions; and

[0036] - Second sub-volume, the surgical robot system is prohibited from entering the second sub-volume.

[0037] The first sub-volume is determined using the method described above.

[0038] - Secondary subvolumes are defined by using information input on treatment plans and / or patient anatomy specific to the region of interest.

[0039] - The information input includes the location of at least one surgical article or anatomical structure, and the second sub-volume includes a set of geometries attached to each of the at least one surgical article or anatomical structure.

[0040] According to a second aspect, the present invention relates to a system for treating a region of interest on a patient's body, the system comprising:

[0041] - A registration phantom configured to be located near the region of interest, the registration phantom including a set of non-transmissive references;

[0042] - An X-ray imaging system configured to acquire at least one 2D X-ray image containing the region of interest and the set of references;

[0043] - A surgical robot system configured to treat a region of interest in a patient's body, the surgical robot system including a robotic arm, an end effector mechanically coupled to the distal end of the robotic arm, and a control unit configured to:

[0044] * Implement the above method to monitor the position of any part of the surgical robot system relative to the restricted access volume;

[0045] * If the control unit detects that at least a portion of the surgical robot system has entered or is about to enter the restricted access volume, it restricts or prohibits the movement of the robotic arm.

[0046] Some preferred but non-limiting features of the above system are as follows, which may be used individually or in any technically feasible combination:

[0047] - The control unit is configured to control the movement of the robot arm by calculating and applying the robot arm's trajectory to process the region of interest, the trajectory of which follows constraints related to the restricted access volume.

[0048] -The control unit is also configured to:

[0049] - Use the above method to define two sub-volumes to determine the restricted access volume;

[0050] - Monitor the position of each part of the surgical robot system to detect whether at least a part of the surgical robot system has entered or is about to enter at least one of the two sub-volumes;

[0051] - If it is detected that a portion of the surgical robot system has entered or is about to enter the first sub-volume, the arm is allowed to move under specific conditions;

[0052] If a portion of the surgical robot system is detected to have entered or is about to enter the second sub-volume, movement of the robotic arm is prohibited.

[0053] - The control unit is configured to follow the following rules to calculate the trajectory of the robotic arm:

[0054] Where possible, the trajectory must prevent every part of the surgical robotic system from entering the restricted access volume;

[0055] - The trajectory can guide the surgical robot system to enter the first sub-volume of the restricted access volume only under specific conditions;

[0056] - The trajectory must prevent each part of the surgical robot system from entering the second sub-volume.

[0057] -The system includes:

[0058] - A positioning system, which is connected to the surgical robot system;

[0059] - A patient tracker, which can be located by a positioning system, is placed on the patient's body and has a known relationship with a registration mold.

[0060] Wherein, the location of the restricted access volume relative to the location of the patient tracker is known, and when the positioning system loses visibility of the patient tracker, the control unit is configured to:

[0061] - Consider that the location where the restricted access volume enters has not changed from the last known location; and

[0062] - Once the positioning system regains visibility of the patient tracker, it updates the location of the restricted access volume. Attached Figure Description

[0063] Other features and advantages of the invention will become apparent from the following description, based on the accompanying drawings, wherein:

[0064] - Figure 1 It is a general overview of the surgical facility, including the operating table, the powered C-arm, and the surgical robot system;

[0065] - Figure 2 The diagram schematically illustrates the electric C-arm, operating table, and patient's body.

[0066] - Figure 3 The diagram schematically illustrates the registration phantom and the patient tracker attached to the patient's bones;

[0067] - Figure 4A A first embodiment of the method according to the invention for defining a restricted access volume is illustrated schematically;

[0068] - Figure 4B A second embodiment of the method according to the invention, which defines a restricted access volume, is illustrated schematically;

[0069] - Figure 5 The illustration schematically depicts an example in which the limitation of the restricted access volume includes the limitation of two sub-volumes according to the method of the present invention;

[0070] - Figure 6 This is a flowchart illustrating a method implemented by the control unit of a surgical robot system to determine a restricted access volume.

[0071] For ease of reading, the figures are not necessarily drawn to scale. In particular, for the sake of drawing, the dimensions of restricted access volumes are shown here as having finite dimensions, but this is not necessarily the case.

[0072] The same reference symbol from one diagram to another represents the same element or the element that performs the same function. Detailed Implementation

[0073] This method can be used to operate robotic systems during surgical procedures on a patient's bones, including but not limited to: implanting orthopedic implants (such as pedicle screws) in the spine, implanting various orthopedic implants in the bones, reducing and fixing fractures during trauma surgery, positioning guides or cannulas in desired locations relative to predefined targets, or inserting catheters or stents during cardiovascular or urological procedures.

[0074] In this regard, the surgical robot system is connected to the X-ray imaging system and can also be connected to the positioning system.

[0075] Figure 1 It is a general overview of the surgical site, including the surgical robot system 100, the operating table 200, the positioning system 300, and the motorized C-arm 400.

[0076] Surgical robot system

[0077] The surgical robot system 100 has a movable trolley 101 and a robotic arm 102 carried by the movable trolley.

[0078] During surgery, the trolley 101 is designed to remain fixed relative to the operating table 200 where the patient P lies, while the robotic arm 102 moves to treat the region of interest R of the patient's body P.

[0079] The mobile trolley 101 can move on wheels 103 and includes at least one handle 104 to allow the operator to easily maneuver and transport the surgical robot system.

[0080] The mobile trolley 101 can be manually actuated, or alternatively, motorized with at least one degree of freedom. Once the mobile trolley has been moved to the desired position relative to the operating table, at least one wheel can be stopped.

[0081] The robotic arm 102 includes multiple translational and / or rotational degrees of freedom. Typically, the robotic arm includes at least six motorized degrees of freedom. For this purpose, the robotic arm includes multiple articulated segments driven by motors with encoders. By convention, the segments are numbered from the proximal end of the robotic arm (which is the end closest to the movable trolley) to the distal end (opposite to the proximal end). Successive robotic arm joints can be rotational or translational. Successive rotations can be orthogonal or parallel. Some parts of the robotic arm may also use parallel mechanisms, such as a hexapod architecture.

[0082] In a preferred embodiment, the robotic arm is constructed from six or seven rotational axes arranged in an anthropomorphic architecture, such as KUKA Iiwa™ or LBR Med™, STAUBLI Puma 200™ or KINOVA Gen 3™. In this anthropomorphic architecture, the first and second axes are substantially orthogonal to each other.

[0083] The robotic arm can be controlled autonomously, manipulated in a collaborative mode (collaborative robot), or remotely controlled using a master control device, based on desired goals and trajectories. Combinations of two or more of these different modes can be used on the same robotic system.

[0084] The surgical robot system 100 includes an end effector 105 for holding a medical device (such as a surgical instrument or tool holder), the end effector being mechanically coupled to the distal end of a robotic arm 102.

[0085] The surgical robot system 100 also includes a control unit 106 configured to controllably move the robotic arm 102. In some embodiments, the control unit is also configured to controllably move at least a portion (e.g., at least one wheel) of the movable trolley 102.

[0086] The control unit 106 includes a processor, a data storage device, and a communication device. The control unit can be advantageously embedded in the movable cart 101. The movable cart may also include switches, such as a power switch, an emergency stop button, etc.

[0087] Control unit 106 is configured as follows:

[0088] - Implement a method for determining the restricted access volume V, which will be described later;

[0089] - Monitor the position of any part of the surgical robot system 100 relative to the restricted access volume V;

[0090] If the control unit detects that any part of the surgical robot system 100 (e.g., the robot arm 102 or the end effector 105) has entered or is about to enter the restricted access volume V, the movement of the robot arm 102 is restricted or prohibited.

[0091] When the robotic arm 102 is controlled in autonomous mode, the control unit 106 is also configured to control the movement of the robotic arm 102 to process the region of interest R and calculate the trajectory of the robotic arm 102, which follows constraints related to the restricted access volume V.

[0092] In other embodiments (not shown), the control unit 106 may be disposed separately from the movable trolley 101 and may be configured to communicate wirelessly or wiredly with the robotic arm 102.

[0093] Control unit 106 may be a single unit of various elements of the control system, such as surgical robot system 100, imaging system 400, and positioning system 300, or a group of units corresponding to each other, each unit controlling a corresponding element of the control system. In the following description, the term "control unit 106" is used indiscriminately to specify one of these cases.

[0094] Positioning system

[0095] The positioning system 300 is configured to locate trackers attached to the patient, robotic arm, end effector, and / or surgical instruments. The positioning system 300 can be selected from a variety of technologies, such as optical positioning (e.g., Aurora from NDI Canada), electromagnetic positioning, or ultrasound positioning.

[0096] exist Figure 1 In the illustrated embodiment, the positioning system includes a camera 300 arranged to detect optical trackers, each of which includes a set of reflective markers having, for example, a spherical shape. Figure 1The diagram shows only one tracker 301 (also referred to as a "robot tracker") attached to the end effector 105, but at least one additional tracker 503 (also referred to as a "patient tracker") attached to the patient is also used, as shown in the image. Figure 3 , 4A As shown in 4B and 5.

[0097] X-ray imaging system

[0098] like Figure 2 As described in more detail, the X-ray imaging system 400 includes at least one X-ray source 401 and at least one X-ray image detector 402. The X-ray imaging system produces at least one 2D X-ray image, which is the result of a cone projection of a patient's anatomy, wherein the tip of the cone is approximately the center point of the X-ray source, and the base of the cone is approximately a portion of the X-ray image detector, which is reached by an X-ray beam collimated in a given shape and orientation.

[0099] For example, the X-ray imaging system can be a conventional C-arm, or any cone-beam computed tomography (CBCT), such as the Surgivisio device (Surgivisio, Giers, France), or Vision FD Vario 3D (Ziehm), CIOSSpin Mobile 3D (Siemens), Airo (Stryker), Loop-X (Brainlab), O-arm (Medtronic).

[0100] Traditional C-arm designs allow the X-ray source and X-ray detector to rotate along the C-shaped gantry 403 while simultaneously acquiring projected images of the patient placed between the X-ray source and X-ray detector positioned on the gantry.

[0101] CBCT features a moving X-ray source and a moving X-ray image detector, both of which have motorized motion, allowing them to move together or independently. CBCT can have a C-arm or O-arm shape. It can be used to acquire a set of 2D X-ray images on an orbital rotation of approximately 180°, which can be combined with translation and from which 3D images can be reconstructed using tomographic algorithms or tomographic synthesis algorithms.

[0102] X-ray imaging systems can be motorized; in particular, a C-arm may include motors that allow horizontal (X and Y directions), vertical (Z direction), and movement about the X direction (defined by angle α), enabling the generation of 2D X-ray images of the patient from virtually any angle. Figure 2As shown, the X-axis is transverse to the operating table 200 on which the patient lies, and the Y-axis (also referred to as the track rotation axis) is parallel to the longitudinal axis of the operating table. Each motor is associated with an encoder that provides the relative position of the medical imaging system with respect to a reference position at any given time. The corresponding position of the imaging system is recorded when a 2D X-ray image is acquired. Thus, each 2D image is recorded in the reference of the imaging system.

[0103] In some embodiments, if the X-ray imaging system is a CBCT, 3D images of the patient can be obtained using the X-ray imaging system itself during surgery. These 3D images are then registered relative to a tracker and / or registration phantom attached to the anatomical structure using known calibration and navigation methods.

[0104] In other embodiments, 3D images can be acquired prior to surgery using a computed tomography (CT) device or another CBCT device. The 3D images of the patient are registered relative to a tracker and / or registration phantom attached to the anatomical structure using a 3D registration method. This method can utilize various techniques, such as (i) using a positioning system to collect surface points and fit them to the anatomical structure, as provided by 7D Surgical (New York City, Canada); or (ii) acquiring 2D X-ray images calibrated relative to the registration phantom attached to the anatomical structure and using them for registration with the 3D images, as provided by the Mazor X Robotic System (Medtronic); or (iii) any registration technique using local ultrasound images, reference points, anatomical points, etc.

[0105] Registration phantom

[0106] At the start of the surgical procedure, the registration phantom 500 is placed on the patient, close to the region of interest R to be treated, such as bone. Preferably, the placement of the registration phantom 500 can be accomplished without any surgical steps, for example, by attaching the registration phantom to the patient's skin using an adhesive (e.g., Figure 4A (as shown in AB and 5) or by attaching the registration phantom to a device already implanted in the patient's bone R for other purposes, such as for attaching the patient tracker 503 to a base 502 on the bone (as shown in AB and 5). Figure 3 (As shown). Alternatively, as... Figure 4A , Figure 4B and Figure 5 As shown, the registration phantom 500 may include a tracker 503. The tracker 503 may be a patient tracker, or an additional tracker referred to as a "phantom tracker".

[0107] The registration phantom 500 includes a set of radiopaque references 501, specifically three or more radiopaque references. Each reference 501 has a known position in the 3D coordinate system of the registration phantom and therefore a known relationship with the geometry of the registration phantom 500.

[0108] Each reference 501 may be a spherical or needle-shaped piece of a radiopaque material (such as steel, stainless steel, or zircon), and its dimensions are known by any method available to a technician. These references 501 are embedded in or supported by supports made of a substantially radiopaque material. In this way, when a 2D X-ray image of the registration phantom is acquired, the reference 501 is visible in the image, while the supports are substantially invisible, or at least do not obstruct the detection of the references in the 2D X-ray image.

[0109] The registration phantom 500 is used here to generate a 3D image from a 2D X-ray image acquired from an imaging system, as previously described, and to define a restricted access volume. In practice, since the registration phantom 500 is typically located close to the patient's skin, it can be assumed that the location and orientation of the registration phantom are closely related to the patient's skin surface characteristics (e.g., location and orientation) near the region of interest R to be treated.

[0110] The information from the registration phantom 500 can then be used to define the restricted access volume V without the need for additional materials, such as additional sensors or acquisition devices, since the registration phantom 500 already exists on the patient as part of the generation of the 3D image.

[0111] Limited access volume

[0112] A restricted access volume V is a volume in which the surgical robot system 100 is configured to have only restricted access. In other words, except under specific conditions, no part of the surgical robot system 100 (robotic arm 102, end effector 105, and even surgical instruments coupled to the end effector, if their dimensions are known to the surgical robot system) is permitted to enter this volume. For example, the surgical robot system 100 may be allowed to enter the restricted access volume V if only a portion of the surgical robot system 100 enters the restricted access volume while the end effector and instruments never enter the restricted access volume. In practice, only a portion of the robotic arm may temporarily enter the restricted access volume without endangering the patient's life in order to properly position the end effector to treat the region of interest. In this particular case, there is no reason to prohibit movement of the robotic arm. In another example, the end effector may be equipped with a tool holder, and depending on the operation, it may be necessary to allow the tool holder to enter the restricted access volume V in a specific area, while the rest of the surgical robot system 100 remains outside the restricted access volume V. A portion of the surgical robot system 100 may also be allowed to enter the restricted volume V in a specific area only during specific steps of the planned surgical procedure.

[0113] The restricted access volume V is selected to surround at least a portion of the region of interest R and the patient's body P to reduce the risk of injury to the patient from the robotic arm 102, particularly during the displacement of the robotic arm 102 to guide the surgical instruments according to the planned trajectory.

[0114] Advantageously, the restricted access volume V comprises at least two sub-volumes, each defining a different security level with different access conditions:

[0115] - First sub-volume V1, the surgical robot system 100 may occasionally enter the first sub-volume V1 under certain conditions;

[0116] - Second sub-volume V2, into which the surgical robot system 100 is prohibited. This second sub-volume V2 is typically associated with vulnerable and vital parts of the patient, and any contact between this second sub-volume V2 and the surgical robot system 100 could result in irreversible damage to the patient.

[0117] In this embodiment, the surgical robot system 100 may enter the restricted access volume V only when it temporarily enters the first sub-volume V1 and never crosses the second sub-volume V2. Alternatively, the surgical robot system 100 may enter the restricted access volume V only when a specific portion of the robot system 100 enters the first sub-volume V1 and no part of the surgical robot system 100 crosses the second sub-volume V2. The second sub-volume V2 may substantially correspond to the patient's spine, including all vertebrae, the spinal cord, and nerve entry points within the spinal cord (together defined as the region of interest). In another embodiment, the second sub-volume V2 may alternatively or additionally consider information entered by the surgeon during preoperative planning of the surgical procedure on 2D and / or 3D images, such as the location of at least one surgical item 600 to be inserted into the region of interest R. Figure 5 As shown. The second sub-volume V2 can be defined manually or automatically.

[0118] The second sub-volume V2 may include or be partially included in the first sub-volume V1. Advantageously, the first sub-volume V1 corresponds to the first boundary of the restricted volume V, while the second sub-volume V2 is used to add an additional layer of security by defining at least one area that prohibits any movement. When the second sub-volume V2 includes areas not included in the first sub-volume V1, and therefore the initial restricted access volume V includes areas not included in the first sub-volume V1, the second sub-volume V2 is used to update the restricted access volume V. In this case, the restricted access volume V corresponds to the union of the first sub-volume V1 and the second sub-volume V2.

[0119] Each sub-volume V1, V2 can include several different volumes, such as Figure 5 As shown, the second sub-volume V2 includes four volumes V2a, V2b, V2c, and V2d, each of which is attached to a surgical item to be inserted into the region of interest R.

[0120] Clearly, a restricted access volume V can include more than two sub-volumes.

[0121] Additionally, certain volumes can be excluded from the restricted access volume V. In practice, in the case of pedicle screw placement, the surgeon can indicate the drilling axis that the robotic arm 102 will have to hold for the drill bit by positioning each pedicle screw. Since the robotic arm 102 and the tool held or guided by it may have to evolve at least partially near these axes during drilling, it may be advantageous to exclude volumes around said axes (e.g., cylinders or cones whose axis of rotation corresponds to the planned drilling axis) from the restricted access volume.

[0122] Area of ​​Interest

[0123] The region of interest R to be treated is usually bone (or, for example, bone). Figure 4A , 4B (and the multiple bones shown in Figure 5), which can be drilled, deburred, and / or milled to place implants or free up some space for any clinical reason.

[0124] Methods for limiting restricted access volume

[0125] Figure 6 This is a flowchart illustrating a method implemented by the control unit 106 of the surgical robot system 100 to determine the restricted access volume V. This flowchart is a non-limiting example, and some steps may be omitted or performed in a different order if appropriate.

[0126] The method for determining the restricted access volume V includes the following steps:

[0127] - Step S1: Acquire at least one 2D X-ray image of a set of references including the region of interest R and the registration phantom 500 through the imaging system 400;

[0128] - Step S2: Use at least one acquired 2D X-ray image to define the phantom coordinate system attached to the registration phantom;

[0129] - Step S3: Determine the orientation of the phantom coordinate system in the selected coordinate system;

[0130] - Step S4: Define a restricted access volume in the selected coordinate system to enclose the region of interest, and calculate the envelope of the restricted access volume based on the orientation of the determined phantom coordinate system in the selected coordinate system.

[0131] In step S1, the imaging system 400 acquires at least one 2D X-ray image containing a set of references 501 including the region of interest R and the registration phantom 500. In one embodiment, this step corresponds to acquiring 2D X-ray images to generate 3D images of the region of interest for the surgeon to use in surgical planning. As is well known to those skilled in the art, at least three references are required to be visible in the 2D X-ray images to determine the orientation of the phantom coordinate system. It is not necessary to see the complete set of references, but the more references visible, the lower the risk of error.

[0132] In step S2, the phantom coordinate system attached to the registration phantom is defined. First, the position of each reference is determined in the coordinate system of the imaging system using at least one 2D X-ray image, or, if a 3D volume is reconstructed, the position of each reference is determined in the coordinate system of the 3D image.

[0133] In one embodiment, if the projection matrix of the imaging system 400 is known, the position of each reference in the imaging system coordinate system can be determined using only one or two 2D X-ray images, without needing to reconstruct the 3D volume using backprojection and known relationships between each reference. The projection matrix takes into account the geometric model of the X-ray imaging system and defines the transformation from 3D points in the imaging system coordinate system to 2D pixels in the 2D X-ray image. This projection matrix can be provided by the manufacturer of the X-ray imaging system or estimated using calibration methods. The more 2D X-ray images with sufficiently different X-ray incident angles available, the more accurate the localization of each reference will be.

[0134] In another embodiment, the projection matrix of the imaging system is unavailable, and multiple 2D X-ray images with sufficiently different X-ray incident angles are required to construct a 3D image using known techniques. Once the 3D image is generated, the positions of the references in the coordinate system of the imaging system or the 3D image are obtained by detecting those references in the 3D image.

[0135] Alternatively, the 3D volume of the region of interest may have been acquired preoperatively using another imaging system and / or in the absence of a registration phantom visible in that 3D volume. In this case, at least one 2D X-ray image can be acquired by the imaging system and then registered with the 3D volume using well-known techniques (e.g., using correlation metrics or finding correspondences between image features) to obtain the location of the reference within the 3D volume.

[0136] Then, the principal plane M of the registration phantom is determined using the location of each determined reference and the known relationship between the reference and the geometry of the registration phantom. This principal plane M can be a theoretical plane representing the principal shape of the registration phantom, or it can correspond to a specific plane of the registration phantom. Specifically, if the registration phantom is attached to the patient's skin with adhesive, this plane can be the contact surface between the registration phantom and the patient's skin; or if the registration phantom 500 does not directly contact the patient's skin, this plane can be the contact surface with a device already implanted in the patient's bone (e.g., the base 502 to which the patient tracker 503 is attached).

[0137] Once the principal plane M of the registration phantom 500 is determined, the intermediate axis is defined as the normal vector of this principal plane. This intermediate axis is used to define the phantom coordinate system, as described below.

[0138] To define the phantom coordinate system, three axes are required. The first axis A1 is defined as the rotation axis Y of the X-ray imaging system 300 used to acquire at least one X-ray image previously used to determine the position of each reference. This first axis can also alternatively be associated with the patient's craniotail axis, or, where the 3D volume is available preoperatively as described above, correspond to the orbital rotation axis Y of the imaging system used to acquire the 3D volume preoperatively. Then, the second axis A2 is determined using the first axis and the intermediate axis previously determined by using a vector product. Finally, similar to the second axis, the third axis A3 is determined using the first and second axes. The resulting first axis A1, second axis A2, and third axis A3 form the phantom coordinate system.

[0139] In step S3, the orientation of the phantom coordinate system is determined in the selected coordinate system.

[0140] In one embodiment, if the positioning system 300 has a fixed position throughout the entire duration of the surgery, the chosen coordinate system is the coordinate system of the positioning system 300 that can position both the patient tracker 503 and the robot tracker 301. To determine the orientation of the phantom coordinate system in the positioning system coordinate system, a known relationship needs to be established between the registered phantom 500 and the locatable elements of the positioning system 300. In practice, the positioning system 300 can access the position of the element in the positioning system coordinate system, and the control unit 106, knowing the relationship between the element and the registered phantom 500, can then determine the orientation of the phantom coordinate system in the positioning system coordinate system. In the first example, the element is the tracker 503, which has a known relationship with the registered phantom 500. The tracker 503 can be directly integrated into the registered phantom 500 (e.g., ...). Figure 4A , 4B (as shown in Figure 5), and may correspond to a patient tracker or an additional tracker different from a patient tracker, referred to as a "phantom tracker". Alternatively, the tracker 503 may have a known mechanical connection with the registered phantom 500, such as both sharing a common base (e.g., Figure 3 (As shown). In the second example, the element is a tracker attached to the imaging system. In this case, the relationship between the registration phantom 500 and the imaging system 400 is known by detecting the position of the registration phantom in the 2D X-ray image or directly in the 3D image reconstructed from the 2D X-ray image using image processing techniques.

[0141] In a preferred embodiment, the selected coordinate system is the coordinate system attached to the patient tracker, also referred to as the "patient coordinate system". This embodiment is advantageous because the patient tracker 503 should have a fixed position relative to the region of interest R throughout the operation. The pose of the phantom coordinate system is then obtained directly by registering the known relationship between the phantom 500 and the patient tracker 503.

[0142] In the first embodiment, the patient tracker 503 is directly integrated into the registration phantom 500 (e.g., Figure 4A , 4B (as shown in Figure 5), or has a known mechanical link with the registration phantom 500, such as both sharing a common base (e.g. Figure 3 (As shown).

[0143] In the second embodiment, the registration phantom 500 is equipped with its own tracker, referred to as the "phantom tracker," which is different from the patient tracker. In this case, the relationship between the registration phantom 500 and the patient tracker is directly obtained through the positioning system 300, which can locate both the patient tracker and the phantom tracker.

[0144] In the following description, the patient coordinate system is selected as the chosen coordinate system. Obviously, any other relevant coordinate system can be selected, and other methods exist for determining the pose of the phantom coordinate system within the selected coordinate system.

[0145] In step S4, the restricted access volume V is defined in the patient coordinate system using the determined pose of the phantom coordinate system. More specifically, the envelope of the restricted access volume is calculated based on the pose of the phantom coordinate system. Furthermore, the restricted access volume includes the region of interest. As previously mentioned, if it is necessary to define the restricted access volume V in a different selected coordinate system, the pose of the phantom coordinate system is determined in that selected coordinate system instead of the patient coordinate system.

[0146] In the first embodiment, the restricted access volume V is defined as the volume below the principal plane M of the registration phantom 500 (assuming the registration phantom is located above the patient's body, such as...). Figure 4A (As shown). In practice, since the registration phantom 500 is typically located close to the patient's skin, the principal plane of the registration phantom 500 can be associated with the surface of the patient's skin. As a result, the envelope of the restricted access volume includes at least a portion of the principal plane M.

[0147] However, this limitation may not always be appropriate, especially when the region of interest R is a vertebra and the patient has significant spinal deformities (e.g., as shown in the image). Figure 4B When the spine is kyphotic or scoliotic (as shown).

[0148] In the second embodiment, particularly applicable when a patient has a spinal deformity, the restricted access volume V is defined by using a “highest point” H of the registered phantom 500. This highest point H of the registered phantom 500 may correspond to a reference 501 or to a specific portion of the registered phantom, such as a corner, which is the highest point in the phantom coordinate system along the third axis. Once the highest point H is determined, the restricted access volume V is defined as the volume below a restrictive plane L that includes the identified highest point H, and the restrictive plane L is orthogonal to the third axis of the phantom coordinate system. In other words, the restrictive plane L is parallel to the plane formed by the first and second axes of the phantom coordinate system and has the third axis of the phantom coordinate system as its normal vector. This restrictive plane serves as an additional safety measure to reduce the risk of excluding important patient body parts from the restricted access volume V when the surface around the region of interest exhibits localized deformities compared to the surrounding surface. As a result, the envelope of the restricted access volume includes at least a portion of the restrictive plane L.

[0149] Furthermore, in both embodiments, at least one dimension of the operating table 200 and / or at least one dimension of the patient's body P can be used to further define the restricted access volume V, thereby calculating the envelope of the volume V. In practice, the patient's body P typically does not protrude from the operating table 200, so it is unnecessary to extend the dimensions of the restricted access volume V beyond the boundaries of the operating table 200. When the patient P is lying on their side on the operating table 200 in a lateral position, with the registration phantom 500 attached to the vertebrae, it is advantageous to consider the patient's width to define the top boundary of the restricted access volume V to allow the surgical robotic system 100 to move over the patient's body P. Furthermore, the restricted access volume V does not need to include the entire patient's body P, because the robotic arm 102 may not be able to reach parts of the patient's body P remote from the region of interest and / or these parts are less susceptible to injury.

[0150] In one embodiment, the restricted access volume V may have an elliptical shape, such as a cylinder, which is extruded from an initial shape of the restricted access volume V. In this example, the cylinder may be defined such that its generatrix is ​​tangent to the principal plane M or the restrictive plane L of the phantom. The dimensions of the patient and / or the table are advantageously used to define the characteristics of the base of the cylinder.

[0151] In another embodiment, the size and shape of the restricted access volume V can be further manually adjusted by the user. For example, the current restricted access volume V can be displayed on the screen as a layer on top of a 3D model of the patient's body or region of interest, and the user can directly adjust the outline of the restricted access volume V.

[0152] Advantageously, as previously stated, the restricted access volume V comprises at least two sub-volumes (such as...) Figure 5(As shown). The first subvolume V1 is defined using the previously described method, and the second subvolume V2 is defined using information input specific to the region of interest R, such as treatment planning and / or patient anatomy. This information input may include the location of at least one anatomical structure (e.g., bone or region of interest), and / or the location of at least one surgical article 600 (e.g., pin, screw, or implant). The second subvolume V2 includes a set of geometries attached to each of the at least one surgical article 600 and / or anatomical structure. For simplicity, the geometry is advantageously a simple shape, such as a cube, sphere, or rectangle, but other more complex forms may be chosen if they are more suitable for the nature of the surgical article 600. This set of geometries does not need to share the same shape and characteristics, and different geometries may be chosen for each different surgical article 600; and / or anatomical structure, the dimensions of which are adjusted according to the dimensions of the relevant surgical article and / or anatomical structure.

[0153] Clearly, more than two sub-volumes can be defined for the restricted access volume V, especially if the surgical robot system 100 needs to have more than two different behaviors associated with different parts of the restricted access volume V.

[0154] As a reminder, the restricted access volume V corresponds to the union of all sub-volumes. The shape of the restricted access volume V can vary relative to the sub-volumes, particularly when the second sub-volume V2 or the additional sub-volume includes regions not included in the first sub-volume V1 or only partially included in the first sub-volume V1. It is possible that some regions are included only in the second sub-volume V2, while some regions are included in both the first sub-volume V1 and the second sub-volume V2.

[0155] Operation of robotic surgical system

[0156] During the surgical intervention, patient P lies on operating table 200, and registration phantom 500 is rigidly attached to patient P near region of interest R.

[0157] For example, in the case of spinal surgery, patient P can lie face down on operating table 200, allowing the surgeon to access a region of interest R that may include one or more vertebrae. In another example, not shown here, patient P can lie on his / her side on operating table 200 for procedures such as tilted lateral interbody fusion to better access the lumbar spine.

[0158] At the start of the surgery, patient P is equipped with a first tracker (referred to as "patient tracker" 503) that can be located by positioning system 300 and a registration phantom 500. Patient tracker 503 and registration phantom 500 have a known relationship, and therefore knowing the position of patient tracker 503 allows knowing the position of registration phantom 500.

[0159] A second tracker 301 (referred to as "robot tracker" 301) may also be mounted on the robotic arm 102 or any subsystem of the surgical robot system 100. The relationship between the robot tracker 301 and the surgical robot system 100 is known, and the robot tracker 301 has a known position on the surgical robot system 100. The robot tracker 301 may also be positioned by the positioning system 300, allowing the control unit 106 to know the position of any part of the surgical robot system 100 relative to the restricted access volume V. This can be achieved using information from the positioning system 300, the relationship between the robot tracker 301 and the surgical robot system 100, and the encoder values ​​of each motor of the robotic arm 102. If the position of the base of the surgical robot system 100 is known and does not change during treatment of the region of interest, the robot tracker 301 may not be necessary.

[0160] 3D images are acquired at the start of surgery using the X-ray imaging system itself (CBCT) or prior to surgery using another imaging system (CT or CBCT). In the latter case, if the 3D images acquired prior to surgery do not include the reference for the registration phantom, at least one 2D X-ray image including the reference for the registration phantom must be acquired as described above.

[0161] The control unit 106 implements the previously described method to determine the restricted access volume V. Therefore, the control unit 106 knows the relationship between the location of the restricted access volume V and the location of the patient tracker 503 in the patient coordinate system, and thus updates it with any movement of the patient tracker 503 (e.g., the patient's breathing).

[0162] Then, the control unit 106 monitors the position of any part of the surgical robot system 100 relative to the restricted access volume V, and if the control unit 106 detects that any part of the surgical robot system 100 has entered or is about to enter the restricted access volume V, it restricts or prohibits the movement of the robot arm 102.

[0163] When the robotic arm 102 is moved automatically by the control unit 106, the control unit 106 is configured to control the movement of the robotic arm 102 by calculating and applying the trajectory of the robotic arm to properly position the end effector to treat the region of interest R, the trajectory conforming to constraints associated with the restricted access volume V. To calculate the trajectory of the robotic arm 102, the control unit 106 is configured to adhere to the following rules:

[0164] Where possible, the trajectory should prevent any part of the surgical robot system 100 from entering the restricted access volume V;

[0165] - The trajectory can guide the robotic surgical system 100 only under specific conditions (such as temporarily or / and partially) into the first sub-volume V1 of the restricted volume V;

[0166] - The trajectory must prevent any part of the surgical robot system 100 from entering the second subvolume V2.

[0167] If the control unit 106 fails to find a trajectory that complies with those rules, the control unit 106 prohibits the movement of the robotic arm 102.

[0168] When the robotic arm 102 (collaborative robot) is manually moved, in order to properly position the end effector 105 to treat the region of interest R, the control unit 106 monitors the position of any part of the surgical robot system 100 throughout the duration of the surgery. If the control unit 106 detects that any part of the surgical robot system 100 enters a restricted access volume V, the control unit 106 restricts or prohibits movement of the robotic arm 102. If the surgical robot system 100 is detected to enter a first sub-volume V1, the control unit 106 may allow movement of the robotic arm 102 under certain conditions as previously described, but if the surgical robot system 100 is detected to enter a second sub-volume V2, the control unit prohibits movement of the robotic arm. Optionally, this monitoring can also be used when the robotic arm 102 is moved automatically by the control unit 106 as additional safety in case the movement of the robotic arm 102 does not follow a calculated trajectory.

[0169] In some embodiments, the control unit 106 is also configured to generate a warning signal if any part of the surgical robot system 100 is less than a predetermined distance (e.g., 30 mm) from the restricted access volume V or any sub-volumes V1, V2 of the restricted access volume V. Advantageously, the control unit 106 can generate different warnings, each associated with a specific sub-volume. These warnings can have various characteristics, such as audible signals, LED color changes, or flashing.

[0170] If the robotic arm 102 is moved manually, the control unit 106 can send a first warning signal to the user that the surgical robot system 100 is about to enter a first sub-volume V1 of the restricted access volume V. The user is then invited to try a new trajectory to locate the robotic arm 102. If the user fails to find such a trajectory, the control unit 106 can allow them to use a portion of the surgical robot 100 to enter the first sub-volume V1, while no part of the surgical robot system 100 will enter the second sub-volume V2. If any part of the surgical robot system 100 moves to a distance less than a predetermined distance from the second sub-volume V2, a second warning will be generated.

[0171] If the positioning system 300 loses visibility of the patient tracker 503 and therefore loses the location of the restricted access volume V, the control unit 106 is configured to:

[0172] - Consider that the location of the restricted access volume V has not changed from the last known location;

[0173] - Once the location system 300 regains visibility of the patient tracker 503, it updates the location of the restricted access volume V.

[0174] If the positioning system 300 loses visibility of the patient tracker 503 for a period of time longer than a predetermined value, the control unit 106 can be configured to send a warning and / or interrupt the movement of the robotic arm 102. In practice, there is a risk that the patient tracker 503 has been damaged or detached from the patient P, requiring intervention from the user before continuing treatment.

[0175] The method described above requires a patient tracker, but it can also be applied without one, or even without a robot tracker. For example, if the robotic arm maintains the registered phantom and the base of the robotic arm is fixed relative to the region of interest, then neither a patient tracker nor a robot tracker is needed. Knowing the kinematics of the robotic arm and the relationship between the phantom and the robotic arm, the pose of the phantom coordinate system can be directly obtained in the robotic arm's coordinate system.

[0176] As a reminder, in the above method, the coordinate system used to define the restricted access volume is the coordinate system attached to the patient tracker, but the technician can choose another coordinate system.

Claims

1. A method for determining a restricted access volume (V) of a surgical robotic system (100), the surgical robotic system including a robotic arm (102) and an end effector (105) adapted to treat a region of interest (R) of a patient's body (P), the registration phantom (500) including a set of radiopaque references (501) located near the region of interest (R), the method comprising: - Acquire at least one 2D X-ray image of the set of references (501) including the region of interest (R) and the registration phantom (500) through the imaging system (300); - Use at least one acquired 2D X-ray image to define the phantom coordinate system attached to the registration phantom (500); - Determine the orientation of the phantom coordinate system in the selected coordinate system; - Define the restricted access volume (V) in the selected coordinate system to include the region of interest, and calculate the envelope of the restricted access volume (V) based on the determined pose of the phantom coordinate system in the selected coordinate system.

2. The method for determining the restricted access volume (V) according to claim 1, wherein, The phantom coordinate system is defined by a first axis, a second axis, and a third axis, and the method includes: - Define the first axis (A1) as the orbital rotation axis (Y) of the X-ray imaging system (300); - Use the at least one 2D X-ray image to define the intermediate axis; - Use the first axis (A1) and the intermediate axis to determine the second axis (A2); - Use the first axis and the second axis to determine the third axis (A3) to generate the phantom coordinate system defined by the first axis, the second axis and the third axis (A1, A2, A3).

3. The method for determining the restricted access volume (V) according to claim 2, wherein, The intermediate axis is defined by: - Use at least one acquired 2D X-ray image to determine the position of each reference (501); - Use the determined position of each reference and the known relationship between the reference (501) and the geometry of the registration phantom (500) to determine the principal plane (M) of the registration phantom (500); - Define the intermediate axis as the normal vector of the principal plane (M) of the registration phantom (500).

4. The method for determining the restricted access volume (V) according to claim 3, wherein, The envelope of the restricted access volume is calculated to include at least a portion of the principal plane (M) of the registration phantom.

5. The method for determining the restricted access volume (V) according to any one of claims 2 to 3, wherein, The steps for limiting the restricted access volume include: - Identify the highest point (H) of the registered phantom (500) in the phantom coordinate system along the third axis; - Calculate the envelope of the restricted access volume to include at least a portion of the restrictive plane, the restrictive plane including the identified highest point of the registered phantom and having a normal vector according to the third axis of the phantom coordinate system.

6. The method for determining the restricted access volume (V) according to any one of claims 4 to 5, wherein, At least one dimension of the operating table (200) where the patient's body (P) is located and / or at least one dimension of the patient's body are further used to calculate the envelope of the restricted access volume (V).

7. The method for determining a restricted access volume (V) according to any one of claims 4 to 6, further comprising having the user manually adjust the size and shape of the restricted access volume (V).

8. A method for determining a restricted access volume (V), comprising at least: - First sub-volume (V1), the surgical robot system (100) is capable of occasionally entering the first sub-volume under certain conditions; and - Second sub-volume (V2), the surgical robot system (100) is prohibited from entering the second sub-volume. The first sub-volume (V1) is determined by the method according to any one of claims 1 to 7.

9. The method according to claim 8, wherein, The second sub-volume (V2) is defined by using a plan of treatment specific to the region of interest (R) and / or information input specific to the patient's anatomy.

10. The method according to claim 9, wherein, The information input includes the location of at least one surgical article (600) or anatomical structure, and the second sub-volume (V2) includes a set of geometries attached to each of the at least one surgical article (600) or anatomical structure.

11. A system for treating a region of interest (R) of a patient's body (P), the system comprising: - A registration phantom (500) configured to be located near the region of interest (R), the registration phantom (500) including a set of nontransparent references (501); - An X-ray imaging system (300) configured to acquire at least one 2D X-ray image containing the region of interest (R) and the set of references (501); - A surgical robot system (100) configured to treat a region of interest (R) of a patient's body (P), the surgical robot system (100) including a robotic arm (102), an end effector (105) mechanically coupled to the distal end of the robotic arm (102), and a control unit (106) configured to: * Implement the method according to any one of claims 1 to 10 to determine the restricted access volume (V); * Monitor the position of each part of the surgical robot system (100) relative to the restricted access volume (V); * If the control unit (106) detects that at least a portion of the surgical robot system (100) has entered or is about to enter the restricted access volume (V), then the movement of the robot arm (102) is restricted or prohibited.

12. The system according to claim 11, wherein, The control unit (106) is configured to control the movement of the robot arm (102) by calculating and applying the trajectory of the robot arm to handle the region of interest (R), the trajectory being subject to constraints related to the restricted access volume (V).

13. The system according to any one of claims 11 to 12, wherein, The control unit (106) is also configured to: - Use the method according to any one of claims 8 to 10 to define two sub-volumes (V1, V2) to determine the restricted access volume (V); - Monitor the position of each part of the surgical robot system (100) to detect whether at least a part of the surgical robot system (100) has entered or is about to enter at least one of the two sub-volumes (V1, V2); - If it is detected that a portion of the surgical robot system (100) has entered or is about to enter the first sub-volume (V1), the arm is allowed to move under specific conditions; If a portion of the surgical robot system (100) is detected to have entered or is about to enter the second sub-volume (V2), movement of the robot arm (102) is prohibited.

14. The system according to any one of claims 11 to 13, wherein, The control unit (106) is configured to calculate the trajectory of the robotic arm (102) according to the following rules: - Where possible, the trajectory must prevent each part of the surgical robot system (100) from entering the restricted access volume (V); - The trajectory can at most guide the surgical robot system (100) to enter the first sub-volume (V1) of the restricted access volume (V) only under specific conditions. - The trajectory must prevent each part of the surgical robot system (100) from entering the second sub-volume (V2).

15. The system according to any one of claims 11 to 14, further comprising: - Positioning system (300), which is connected to the surgical robot system (100); - A patient tracker (503), which can be located by a positioning system (300), is set on the patient's body (P) and has a known relationship with the registration phantom (500). Wherein, the location of the restricted access volume (V) relative to the location of the patient tracker (503) is known, and when the positioning system (300) loses visibility of the patient tracker (503), the control unit (106) is configured to: - It is assumed that the location of the restricted access volume (V) has not changed from the last known location; and - Once the positioning system (300) regains visibility of the patient tracker (503), it updates the location of the restricted access volume (V).

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