Collaborative medical robots for reliable instrument guidance

Abstract

The present invention relates to a medical robot (10) for assisting a practitioner during a medical intervention on a relevant anatomical part of a patient (20). The medical robot comprises a robotic arm (13) provided at one end with a tool guide (14) intended to guide a medical instrument (15). The medical robot (10) also comprises a control device (12) configured to control the movement of the robotic arm (13). The tool guide (14) is coupled to a force sensor. When the medical robot (10) is used in a "collaborative manual control" mode, the control device (12) is configured to determine, using the force sensor, a force exerted by the practitioner on the tool guide (14) and to calculate a speed of movement of the tool guide based on a gain factor applied to the determined force. Advantageously, the value of the gain factor is variable and is calculated based on the determined force.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention is in the field of robotic devices for assisting practitioners during medical or surgical procedures. More particularly, the present invention relates to a medical robot including a robotic arm with a tool guide for guiding and releasing a medical instrument during a minimally invasive or percutaneous medical procedure. [Background technology]

[0002] Conventional technology Medical procedures performed by minimally invasive or percutaneous means may require a practitioner to insert one or more medical instruments (e.g., needles, probes, catheters, etc.) into a patient's body to a given depth to reach a targeted anatomical region (e.g., the liver, lungs, kidneys, or a tumor within a bone).

[0003] When the insertion movements of the medical instrument are performed entirely by the practitioner, the outcome of the procedure depends to a large extent on the practitioner's skill. The precision of the movements can be improved thanks to the assistance of a remotely controlled medical robot. In this case, the success of the procedure still depends in part on the skill of the practitioner, and medical images of the patient must be acquired continuously, which involves exposing the patient to large amounts of radiation.

[0004] To further improve the precision of the insertion movements and limit the radiation dose to the patient, it is possible to use an automatically controlled robotic arm. The robotic arm may be equipped with tool guides for guiding the medical instrument. The practitioner indicates, for example on a pre-intervention medical image, the trajectory that the medical instrument needs to follow to reach the target area of ​​the relevant part of the patient's anatomy, and the robotic arm is automatically displaced into place, allowing the tool guide to guide the medical instrument according to the planned trajectory.

[0005] It is advantageous for the practitioner to be able to manually displace the robotic arm in order to bring the tool guide toward the relevant portion of the patient's anatomical structure or to release the tool guide after (optionally partial) insertion of the medical instrument. When the robotic arm is manually displaced by the practitioner and when the tool guide is relatively far from the relevant portion of the patient's anatomical structure, the movement of the robotic arm needs to be smooth and responsive. On the other hand, when the tool guide is relatively close to the relevant portion of the patient's anatomical structure, the movement of the robotic arm needs to be controlled with precision and at a slow speed in order to reach the position for insertion of the medical instrument accurately and without the risk of injuring the patient with the medical instrument or the tool guide. It is also necessary to avoid jerky movements of the robotic arm caused by the practitioner's trembling.

[0006] For this reason, it can be envisaged to frequently carry out a survey of the force exerted by the practitioner by means of an accelerometer to determine whether tremors are present or not. However, this type of solution is relatively complex to implement and requires the incorporation of an additional sensor (accelerometer) into the medical robot.

[0007] For example, during insertion of a medical instrument into a patient's body, measures must be taken to ensure that the patient cannot be harmed by the medical instrument during the procedure, even if the patient makes an unexpected movement while the robotic arm is guiding the medical instrument. Medical instruments are typically inserted while the patient is apneic. Therefore, it is also necessary to ensure that the patient cannot be harmed by the medical instrument if respiratory movements resume before the medical instrument is released from the tool guide. Summary of the Invention [Problem to be solved by the invention]

[0008] Summary of the Invention SUMMARY OF THE INVENTION It is an object of the present invention to obviate some or all of the disadvantages of the prior art, especially those mentioned above. [Means for solving the problem]

[0009] To this end, according to a first aspect, the present invention proposes a medical robot for assisting a practitioner during a medical procedure on a relevant part of a patient's anatomy. The medical robot comprises a robotic arm including at its distal end a tool guide designed to guide a medical instrument. The medical robot also comprises a control device configured to control the displacement of the robotic arm. The tool guide is coupled to a force sensor. When the medical robot is used in a "collaborative manual control" mode, the control device is configured to determine, by means of the force sensor, a force exerted on the tool guide by the practitioner, and to calculate a velocity of displacement of the tool guide according to a gain factor applied to the force so determined. Advantageously, the value of the gain factor is variable and is calculated according to the force exerted on the tool guide by the practitioner. The control device is configured to control the displacement of the robotic arm according to the velocity so calculated.

[0010] Therefore, the practitioner displaces the robot arm by manually applying a force to a tool guide fixed to the end of the robot arm. The force sensor enables the control device to control the speed of the robot arm's displacement according to the force applied by the practitioner. In fact, the speed of the tool guide's displacement is calculated by applying a gain factor to the force applied to the tool guide by the practitioner. The force applied to the tool guide by the practitioner is determined by the control device based on the forces and moments measured by the force sensor through a series of operations that may include, for example, filtering, noise reduction, compensation for the weight of the tool guide, and transposition of the tool guide to a reference point. The greater the force applied to the tool guide by the practitioner, the faster the speed of the tool guide's displacement calculated by the control device. Therefore, when the tool guide is relatively far from the patient and the practitioner applies a significant force to the tool guide, the robot arm is displaced quickly, smoothly, and responsively. On the other hand, when the practitioner applies only a small force to the tool guide because the tool guide is close to the patient's body, the robot arm is displaced at a slow speed to ensure accuracy and safety.

[0011] Furthermore, as described below, the gain coefficient varies according to the force applied to the tool guide by the practitioner, thereby making it possible to avoid jitter in the displacement of the robot arm caused by tremors by the practitioner (tremors correspond to low amplitude forces that vary at high frequencies).

[0012] For example, the gain factor is the force exerted by the practitioner on the tool guide at a minimum value F min and the maximum value F max When the force changes between

[0013] In particular embodiments, the invention may also include one or more of the following characteristics, taken individually or according to all technically possible combinations:

[0014] In certain embodiments, the gain factor corresponds to the proportional parameter of a proportional-integral-derivative compensator implemented by the controller.

[0015] Using a control loop, the controller calculates the velocity of the tool guide displacement, which is intended to counteract the force exerted by the practitioner. For this purpose, a PID compensator can be used. PID is an acronym for proportional, integral, and derivative. Closed-loop control systems are commonly used in the industry. In fact, the present invention is based on the hypothesis that movements generated by low-amplitude forces exerted by the practitioner will contain tremors. Therefore, the proposed solution does not require frequent analysis to detect tremors. Adopting this hypothesis simplifies the problem and makes it possible to use a PID compensator.

[0016] In certain embodiments, the controller is also configured to prevent displacement of the tool guide in at least one direction.

[0017] The term "direction" corresponds to a degree of freedom of the tool guide in the three-dimensional reference system (x, y, z) in which it is integrated. This direction may in particular be a translation along each of the axes x, y or z, or a rotation around each of these axes.

[0018] This type of arrangement allows for controlled displacement of the robotic arm to prevent the tool guide from colliding with the medical instrument when the robotic arm is released, for example, after partially or fully inserting the medical instrument into the patient's body and releasing the medical instrument from the tool guide.

[0019] In certain embodiments, the controller is also configured to limit the displacement of the tool guide in a single direction, for example, corresponding to a major axis of the tool guide.

[0020] This type of arrangement makes it possible, for example, to control the displacement of the robotic arm in order to bring it to a position corresponding to the position at which the medical instrument is inserted.

[0021] In a particular embodiment, the value of the gain factor is: [Number 1]

number

[0022] In certain embodiments, the control device is configured to calculate the velocity of the displacement of the tool guide according to the distance between the current position of the tool guide and the target position that the tool guide needs to reach.

[0023] In particular, this type of arrangement allows for further limiting the speed of the tool guide's approach as it approaches its target location, enhancing precision and safety when the medical instrument is near the relevant portion of the patient's anatomy.

[0024] In certain embodiments, the robotic arm is an articulated arm having at least six degrees of freedom.

[0025] The use of at least six degrees of freedom in the robotic arm makes it possible to ensure that the tool guide can reach any position in space. Furthermore, if the medical instrument has axisymmetrical properties (e.g., if the medical instrument is a needle), five degrees of freedom are sufficient, since rotation around the axis of symmetry of the medical instrument is not necessary. This additional degree of freedom allows for redundancy situations and for the robotic arm to have an infinite number of possible configurations for a given position. This provides a degree of flexibility, since the practitioner can select the optimal configuration of the robotic arm according to, for example, the constraints inherent in the procedure room (space available to medical staff, the presence of obstacles, visibility of the tool guide by any navigation system, etc.).

[0026] In certain embodiments, when the medical robot is used in a "medical instrument insertion" mode, the controller is configured to prevent any displacement of the tool guide and to determine, using a force sensor, the force exerted on the medical instrument. The tool guide includes means for automatically releasing the medical instrument upon command from the controller. The controller is configured to command the tool guide to release the medical instrument when the force exerted on the medical instrument is greater than a predetermined threshold or when the change in the force exerted on the medical instrument is greater than a predetermined threshold over a given period of time.

[0027] This type of arrangement allows for quick release of the medical instrument during the insertion phase of the medical instrument (i.e., when the medical instrument is held in the tool guide to guide its insertion into the patient's body) if, for example, the patient causes unexpected forces on the medical instrument as a result of breathing movements while the patient should be apneic.

[0028] In certain embodiments, the tool guide includes at least one marker that can be detected by the navigation system, and the controller: - receiving, from the navigation system, first information regarding a position of the tool guide relative to a reference of the navigation system; - receiving second information from the navigation system regarding a target position, relative to the navigation system, that the tool guide needs to reach; - determining a target position relative to the medical robot using the second information; - In "automatic control" mode, the robot arm is displaced so that the tool guide reaches the target position without the intervention of the practitioner. It is configured as follows.

[0029] This type of arrangement allows the robotic arm to automatically and precisely displace the tool guide to a target location where a medical instrument can be inserted into the patient's body to perform a surgical procedure.

[0030] In particular, the target position of the tool guide can be determined according to a trajectory that the medical instrument needs to follow, which is planned in the pre-intervention medical image. To this end, in certain embodiments, the second information corresponds to the position of a patient fiducial, which is intended to be positioned near a relevant portion of the patient's anatomical structure in a reference of the navigation system. The patient fiducial includes at least one marker that can be detected by the navigation system and at least one radiopaque marker. The trajectory is defined relative to the position of the patient fiducial using the pre-intervention medical image, in which the relevant portion of the patient's anatomical structure and the radiopaque marker of the patient fiducial are visible. The control device is configured to determine the target position of the tool guide from the position of the patient fiducial and from the planned trajectory.

[0031] In certain embodiments, the control device: - storing the position of the tool guide at the first moment relative to the position of the patient reference as a reference position; - determining whether the difference between the position of the tool guide at the second instant and the reference position is below a predetermined threshold; It is configured as follows.

[0032] This type of arrangement is particularly advantageous in situations where, for example, after partially inserting a medical instrument, the robotic arm needs to be released to allow medical images to be acquired to verify whether the medical instrument has been properly inserted, and then the robotic arm needs to be brought back to the initial position where the medical instrument was inserted, for example to finish inserting the medical instrument.

[0033] In certain embodiments, the tool guide includes means for automatically releasing the medical instrument upon command of the controller, the controller being configured to command the tool guide to release the medical instrument when the controller receives information from the navigation system indicating an unexpected displacement of the patient reference.

[0034] Therefore, it is possible to avoid injuring the patient with the medical instrument when the patient makes an unexpected movement while inserting the medical instrument into the patient's body.

[0035] Presentation of drawings The invention will be better understood on reading the following description, given by way of non-limiting example and presented with reference to FIGS. [Brief explanation of the drawings]

[0036] [Figure 1] 1 is a schematic diagram of a medical robot according to the present invention for assisting a practitioner during a medical procedure on a relevant part of a patient's anatomy; FIG. [Figure 2] FIG. 1 is a schematic diagram of a robotic arm of a medical robot. [Figure 3] FIG. 1 is a schematic diagram of a tool guide designed to be fixed to the end of a robot arm. [Figure 4] FIG. 10 is a diagram of a tool guide showing an apparatus for holding a medical instrument at the end of the tool guide. [Figure 5] 1 is a diagram of a tool guide showing the positioning of a medical instrument in the tool guide as well as markers that can be detected by a navigation system. [Figure 6] FIG. 1 is a schematic diagram of a patient fiducial designed to be positioned near relevant portions of the anatomy on a patient. [Figure 7] 1 is a diagram of the collaboration of a medical robot and a navigation device according to the present invention; [Figure 8] In particular, it comprises graphs representing the velocity and acceleration experienced by the tool guide according to the force exerted on the tool guide by the practitioner, where the velocity is defined according to a constant gain factor applied to the force exerted. [Figure 9] If the velocity is defined according to a variable gain factor applied to the applied force, with the gain factor varying according to the applied force, then the graph will be similar to that shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0037] In these drawings, the same reference numbers refer to the same or similar elements from one drawing to the next. For clarity, elements shown are not necessarily to scale unless so stated.

[0038] Detailed Description of Embodiments of the Invention 1 shows a schematic representation of a medical robot 10 according to the present invention, which can be used to assist a practitioner during a medical procedure on a relevant part of the anatomy of a patient 20 positioned on a treatment table 21.

[0039] A non-limiting example is when used in medical procedures performed by minimally invasive or percutaneous means. This type of procedure generally requires the practitioner to insert one or more medical instruments (e.g., needles, probes, catheters, etc.) into the patient's body to a given depth to reach a target anatomical region in a relevant portion of the anatomy (e.g., a tumor in the liver, lung, kidney, etc.).

[0040] The medical robot 10 includes a base 11. In a considered example, the base 11 of the medical robot 10 is equipped with motorized wheels, which allow the medical robot 10 to be displaced in different directions by translational and / or rotational movements.

[0041] The medical robot 10 also includes an articulated robotic arm 13, one end of which is connected to the base 11. A guide tool 14 designed to guide a medical instrument 15, such as a needle, probe, catheter, electrode, etc., is fixed to the other end of the robotic arm 13. Thus, the medical robot 10 can be used to help the practitioner position, hold, or guide the medical instrument 15 during a medical procedure. Thus, the medical robot 10 serves as a third hand for the practitioner.

[0042] In the considered example shown in FIG. 2 , the robot arm 13 includes six swivel joints 131-136, providing six degrees of freedom and allowing the medical instrument 15 to be positioned and / or displaced anywhere in three-dimensional space. Advantageously, the joints 131-135 of the robot arm 13 are not aligned but offset from one another, thereby allowing for a greater number of possible configurations of the robot arm 13. Each joint includes at least one encoder that allows its angular position to be determined in real time. Thus, the configuration of the robot arm 13 corresponds to a set of parameter values ​​(e.g., values ​​of the degrees of rotation for each joint) assumed by the joints 131-136. The swivel joint 136 corresponds to rotation around the primary axis of the tool guide 14. However, it should be noted that rotation does not necessarily occur around the axis of symmetry of the medical instrument (indeed, five degrees of freedom are sufficient for guiding and releasing a medical instrument). This additional degree of freedom allows for a redundant situation and makes it possible to have an infinite number of possible configurations of the robot arm 13 for a given position of the tool guide 14. This redundant situation is particularly advantageous for adapting to constraints related to the patient position or the configuration of the treatment room.

[0043] As shown in FIG. 3 , the tool guide 14 is fixed to the robot arm 13 using a flange 17. The tool guide includes a main axis 145, represented by a dashed line in FIG. 3 . The tool guide 14 is coupled to a force sensor 16 to enable the controller 12 to determine the force exerted on the tool guide 14. This force may be exerted by the practitioner, in particular when the practitioner manually displaces the robot arm 13. This force may also correspond to a force exerted on the tool guide 14 by the patient's body via the medical instrument 15 (e.g., as a result of the patient's accidental movement during insertion of the medical instrument).

[0044] It should be noted that the force sensor makes it possible to measure the total force (including not only the force exerted by the practitioner, but also the weight of the tool guide 14, the weight of the medical instrument 15, etc.) that corresponds to the result of the forces and moments that the force sensor 16 is subjected to. The control device is configured to determine the force exerted by the practitioner on the tool guide 14 according to the result of the forces and moments that the force sensor 16 is subjected to. For this purpose, it is necessary, for example, to subtract from the total force the force corresponding to the weight of the tool guide 14 (this force corresponds to the weight of the medical instrument 15 when an instrument is held by the tool guide 14), the torque due to the difference between the measurement point and the center of gravity of the tool guide, and / or any corrections associated with measurement noise. It may also be envisaged to perform filtering on the measurements made by the force sensor 16.

[0045] As shown in FIGS. 4 and 5 , the tool guide 14 includes a body 141 with a base 142 designed to be fixed to the flange 17 using a screw 143, and a retention system 146 including two parts that are movable relative to each other. The retention system 146 is designed to hold the medical instrument 15 at the end of the body 141 of the tool guide 14 opposite the base 142. The two movable parts of the retention system 146 can be driven by a drive system, such as a gear, a cam, a screw with inverted threads, and / or a linear actuator, to block or release the medical instrument 15. The linear actuator can be reversible (so that the retention system 146 of the tool guide 14 can be released manually or automatically upon command from the control device 12) or irreversible (so that the retention system 146 of the tool guide 14 can be released only automatically upon command from the control device). The tool guide 14 can be enabled to guide medical instruments of different diameters, for example. For example, this type of guide can guide a medical instrument, the diameter of which is between 11 and 21 gauge, a unit of measurement commonly used to define the outer diameter of a medical instrument such as a needle, probe, or catheter (11 gauge corresponds to an outer diameter of 2.946 mm; 21 gauge corresponds to an outer diameter of 0.812 mm).

[0046] 1, the medical robot 10 includes a controller 12 configured to control the displacement of a robotic arm 13. The controller 12 includes, for example, one or more processors 122 and a memory 121 (magnetic hard disk, electronic memory, optical disk, etc.), in which a computer program product is stored in the form of a set of program code instructions that are executed to implement the different steps of a method for positioning the robotic arm 13.

[0047] As shown in Fig. 7, a navigation system 30 can be used to provide the control device 12 of the medical robot 10 with information about the current position of the tool guide 14 and the target position that the tool guide needs to reach. The provided current position and target position are, for example, first defined in the reference of the navigation system 30 and then converted by the control device 12 to positions in the reference of the medical robot 10. The control device can then be configured to automatically displace the robot arm 13 to reach the target position (in a so-called "automatic control" mode, without intervention by the practitioner). The navigation system 30 and the control device 12 of the medical robot 10 can exchange data by means of communication (wired or wireless).

[0048] In this application, the term "position" corresponds to the combination of position and orientation of an object in a given reference, which is generally a three-dimensional coordinate system. The term "pose" is used in Anglo-Saxon literature to denote this combination of position and orientation of an object in space.

[0049] In the example considered, the navigation system 30 is an optical navigation system. The navigation system 30 includes at least two optical sensors 31, which correspond for example to the two sensors of a stereo camera operating in the infrared or visible light field.

[0050] As shown in Figures 4 and 5, the tool guide 14 includes a stud 144 designed to receive an optical marker 147. Advantageously, the tool guide 14 includes at least three optical markers 147 so that the position of the tool guide 14 can be determined in three spatial dimensions of the reference frame of the navigation system 30. The respective positions of the tool guide's optical markers 147 relative to one another are known a priori by the navigation equipment 30 and / or the control device 12. Advantageously, the geometric form of each optical marker 147 may also be known intuitively. In the example shown in Figure 5, the optical markers 147 have a spherical shape.

[0051] The use of at least three optical markers 147 makes it possible to define a direct orthonormal three-dimensional reference with a plane, and therefore with an axis z perpendicular to the plane, and axes x and y on the plane, making the reference orthogonal. This therefore makes it possible to determine the position and orientation of the reference formed from the optical markers 147 representing the tool guide 14. The three axes x, y and z make it possible to define six degrees of freedom, namely a translation along each of the axes x, y or z, and a rotation around each of these axes.

[0052] The optical markers 147 may be passive or active. Passive optical markers reflect optical radiation emitted by another element, such as the navigation system 30. Passive optical markers may correspond, for example, to reflective spheres that can be detected by an infrared stereo camera (such as those used in the Polaris® navigation system produced by Northern Digital Inc.) or black and white patterns that are visible by a stereo camera (such as those used in the MicronTracker® navigation system by ClaroNav). Active optical markers themselves emit optical radiation, such as infrared radiation, that can be detected by the navigation system 30.

[0053] As shown in FIG. 7, the assembly of markers 147 present on the tool guide 14 corresponds to the robot datum 18 .

[0054] However, it should be noted that a single optical marker with a distinctive geometric form in three dimensions may be used instead of the assembly of spherical optical markers 147 .

[0055] The patient fiducial 22 is positioned near the relevant portion of the patient 20's anatomy. FIG. 6 shows a schematic representation of the patient fiducial 22. The patient fiducial 22 includes at least three optical markers 23, allowing the position of the patient fiducial 22 to be determined in three spatial dimensions of the reference frame of the navigation system 30. The relative positions of the optical markers 23 of the patient fiducial 22 relative to one another are intuitively known by the navigation system 30 and / or the control device 12. Advantageously, the geometric form of each optical marker 23 may also be intuitively known. In the example shown in FIG. 6, the patient fiducial 22 includes three spherical optical markers 23. The spherical shape allows for optimal reflection of optical radiation. The explanations previously given for the active or passive optical markers 147 of the tool guide 14 also apply to the optical markers 23 of the patient fiducial 22. Again, it may be envisioned that a single optical marker with a distinctive geometric form in three dimensions may be used instead of the three spherical optical markers 23.

[0056] In the following description, it is considered, by way of example and without limitation, that the optical sensor 31 and the different optical markers 147, 23 of the navigation system 30 are designed to operate with infrared-type optical radiation. It is also considered that the optical markers 147, 23 are passive markers. The optical sensor 31 is configured to emit infrared radiation. This infrared radiation is reflected by the different optical markers 147, 23 towards the optical sensor 31. The optical sensor 31 is configured to receive this reflected infrared radiation. The navigation system 30 can thus determine the distance between the optical markers 147, 23 and the optical sensor 31 by measuring the time it takes for the infrared radiation to complete the distance between the optical sensor 31 and the optical markers 147, 23 and back. By knowing the distance between each optical marker 147, 23 and each optical sensor 31, and by intuitively knowing the relative positioning of the optical markers 147, 23 on the tool guide 14 and patient reference 22, it is possible to determine the position of the tool guide 14 and patient reference 22 in the reference system of the navigation system 30.

[0057] The target location that the tool guide 14 needs to reach can be defined in particular from the position of the patient fiducials 22. For this purpose, as shown in FIG. 6 , the patient fiducials 22 also include radiopaque markers 24, which are visible in medical images acquired by a medical imaging device (e.g., by tomodensitometry, by magnetic resonance, by ultrasound, by tomography, by positional emission, etc.). The respective positions of the radiopaque markers 24 relative to one another are intuitively known by the navigation equipment 30 and / or the control device 12. Advantageously, the geometric form of the radiopaque markers 24 can also be intuitively known. Preferably, the patient fiducials 22 include at least three radiopaque markers 24. The radiopaque markers 24 can be, for example, ceramic balls. However, it should be noted that a single radiopaque marker with a distinctive geometric form in three dimensions can be used instead of the three spherical radiopaque markers 24.

[0058] It is therefore possible to plan a medical procedure from a pre-interventional medical image 40 of the patient comprising the patient fiducials 22. This pre-interventional medical image 40 is stored in the memory 121 of the control device 12. It is therefore possible to define from the pre-interventional medical image 40 a target location that the tool guide 14 needs to select in order to guide the medical instrument 15 to perform the medical procedure. The planning includes determining a trajectory 41 that the medical instrument 15 (e.g., a needle) needs to follow between an entry point in the skin of the patient 20 and a target point (e.g., a tumor) within the relevant part of the patient's anatomical structure in the pre-intervention image 40. The fiducials 42 in FIG. 7 represent an assembly of radiopaque markers 24 of the patient fiducials 22, which are visible in the pre-intervention image 40 (and therefore represent an image of the patient fiducials 22 in the pre-intervention image 40). Therefore, a target location of the tool guide 14 that enables following the trajectory 41 can be defined relative to the location of the patient fiducials 22.

[0059] It should be noted that the determination of the trajectory can also be performed on pre-operative images acquired several days before the procedure (the images are acquired without the patient fiducials), so the pre-operative images can be reset with pre-intervention images 40 where the patient fiducials are visible to obtain the relative position of the patient fiducials 22 with respect to the trajectory.

[0060] In the present example, the navigation system 30 is configured to provide the medical robot 10's controller 12 with the current position of the tool guide 14 in the reference of the navigation system 30. However, the medical robot 10's controller 12 knows the current position of the tool guide 14 in the reference frame of the medical robot 10 (via the encoders of the joints 131-136). Therefore, the controller 12 can determine the transformation to perform to define a position in the reference frame of the medical robot 10 from the position in the reference frame of the navigation device 30. The navigation system 30 is also configured to provide the medical robot 12 with the position of the patient fiducial 22 in the reference of the navigation system 30. Therefore, the controller 12 can define the position of the patient fiducial 22 in the reference frame of the medical robot 10. However, thanks to the pre-intervention images 40, the medical robot 10's controller 12 knows the position of the target position that the tool guide 14 needs to reach relative to the position of the patient fiducial 22. Therefore, the controller 12 can determine the target position that the tool guide 14 needs to reach from the information provided by the navigation system 30. Therefore, the control device 12 can be configured to automatically displace the robotic arm 13 to reach the target position (in a so-called "auto-control" mode, without practitioner intervention).

[0061] The displacement of the robot arm 13 depends, for example, on the selection of a control mode on the user interface of the medical robot 10 and the activation of the selected mode by the control pedal 19 .

[0062] The so-called "collaborative manual control" mode corresponds to a mode in which the practitioner himself can manually displace the robot arm 13, but the control of the displacement of the robot arm 13 is by the control device 12 (to limit the speed and / or possible direction of the displacement of the robot arm 13).

[0063] The so-called "automatic control" mode corresponds to a mode in which the robot arm 13 is fully controlled by the control device 12. The robot arm 13 is therefore displaced automatically, without intervention by the practitioner.

[0064] There are several "cooperative manual control" modes.

[0065] The so-called "approach coordinated manual control" mode corresponds, for example, to a mode in which the practitioner displaces the robotic arm 13 to bring the guide tool 14 toward an approach position 101 that is relatively close to the relevant part of the patient's anatomy and in which the robotic arm 13 is in the field of view of the navigation system 30. In this mode, it is advantageous to control the speed of the displacement of the robotic arm 13 according to the force exerted by the practitioner on the robotic arm 13. In this mode, displacement of the robotic arm 13 is generally allowed in all directions.

[0066] Therefore, the robot arm can be automatically displaced (in "automatic control" mode) from the approach position 101 to the insertion position 102. The insertion position 102 corresponds to the target position where the tool guide 14 needs to be positioned to enable the medical instrument 15 to follow a planned trajectory.

[0067] The so-called "release-coordinated manual control" mode corresponds to a mode in which, for example, after partial insertion of the medical instrument 15 into the body of the patient 20, the medical instrument 15 can be released from the holding device 146 of the tool guide 14, and the robotic arm 13 can be manually released by the practitioner from the insertion position 102 towards the release position 103. This type of arrangement makes it possible to move the patient 20 after partial insertion of the medical instrument 15 in order to generate a control medical image (e.g., to verify that the trajectory followed by the medical instrument corresponds to the planned trajectory). In this mode, it may be advantageous to configure the control device 12 to control the robotic arm 13 to prevent displacement of the tool guide 14 in at least one direction, or to limit the displacement of the tool guide 14 according to a single direction corresponding to the main axis 145 of the tool guide 14 (the release direction follows the main axis 145 of the tool guide 14 in the direction from the holding device 146 towards the base 142). According to certain embodiments, when the "released coordinated manual control" mode is activated, the controller 12 is configured to store as a reference position the current position of the tool guide 14 relative to the position of the patient reference 22. The reference position is therefore the position of the tool guide 14 at the first instant t1 when the "released coordinated manual control" mode is activated.

[0068] The so-called "return coordinated manual control" mode corresponds to a mode in which the robot arm 13 is manually displaced by the operator so that, for example, after generating a control image, the tool guide 14 returns to the reference position recorded when the "release coordinated manual control" mode was selected. This reference position corresponds to the insertion position 102 (the target position to which the tool guide 14 needs to reach). Therefore, the "return coordinated manual control" mode is used to bring the tool guide 14 from the release position 103 to the insertion position 102 to complete the insertion of the medical instrument 15. During the displacement, it is important that the tool guide 14 does not exceed the extent of the insertion position 103 (in other words, the tool guide 14 may not be brought to the correct position to complete the insertion, and there may be a collision between the partially inserted medical instrument and the tool guide 14). It may be advantageous to control the robot arm 13 to limit the displacement of the tool guide 14 in a direction along its main axis 145 (the return direction follows the main axis 145 of the tool guide 14 in the direction from the base 142 towards the holding device 146). Furthermore, it may be advantageous to configure the control device 12 to control the speed of displacement of the tool guide 14 according to the distance between the current position of the tool guide 14 and the target position (corresponding to the recorded reference position) that the tool guide 14 needs to reach. Therefore, at a second instant t2, the control device 12 is configured to calculate the difference between the position of the tool guide at the second instant t2 and the reference position (the position of the tool guide 14 at the first instant t1). The speed of displacement of the tool guide 14 is controlled so that the shorter the calculated distance (i.e., the closer the tool guide 14 is to its target position), the lower the speed of displacement until it reaches zero speed when it reaches the target position. The control device 12 is configured to determine whether the difference between the position reached by the tool guide 14 and the reference position is below a predetermined threshold. In this case, the target position is considered to have been reached. It should be noted that the position of the tool guide 14 is defined relative to the position of the patient reference 22. Once the target position has been reached, the practitioner may terminate the insertion of the medical instrument 15. The predetermined threshold is for example equal to 1 mm, or 0.1 mm, or even 0.03 mm.

[0069] When the "collaborative manual control" mode is activated, the practitioner displaces the robot arm 13 by manually applying a force to the tool guide 14. However, the displacement of the robot arm 13 is controlled by the control device 12, which provides force control (control of the speed of the displacement of the tool guide 14) and position control (control of the direction of the displacement of the tool guide 14).

[0070] The force control is governed by an admittance control law. The speed of displacement of the tool guide 14 is controlled by the control device 12. The speed of displacement of the tool guide 14 is calculated according to the force exerted on the tool guide 14 by the practitioner, said force being determined by the control device using the force sensor 16.

[0071] More specifically, the force so determined corresponds to the input data of a control loop, the output data of which is the Cartesian velocity of displacement of the tool guide 14. The control loop is operated, for example, at a frequency of 125 Hz (in which case the value of the velocity of displacement of the tool guide 14 is updated every 8 ms).

[0072] The control device 12 calculates the velocity of the displacement of the tool guide 14, allowing it to compensate for the force applied to the tool guide by the practitioner. In other words, the difference (also known as the error) between the force value determined at the current time (at each iteration of the control loop) and the required force value (zero force) is equal to the determined force. The control loop algorithm is designed to define the velocity of the displacement, which tends to zero the error. To correct this error, a PID compensator can be used (PID is an acronym for "proportional, integral, derivative" and is commonly used in the industry for closed-loop control systems). The error (i.e., the difference between the determined force and the required force) is input data for the PID compensator, which provides the velocity as output, allowing to obtain an error that tends to zero.

[0073] In what follows, for simplicity, we will only consider the "proportional" part of the PID compensator, in other words as if the "integral" and "derivative" parts were zero.

[0074] The velocity of the displacement of the tool guide 14 is calculated by applying a gain factor to the determined force: [Number 2] |v|=G×|f| (where G is a gain coefficient, |f| is the force determined by the controller (the force exerted by the practitioner on the tool guide 14), and |v| is the velocity of displacement of the tool guide 14). The gain factor G corresponds to the gain factor of the "proportional" part of the PID compensator.

[0075] In other words, the greater the force applied by the practitioner to the tool guide 14, the faster the speed of displacement of the tool guide 14 calculated by the control device 12. Therefore, when the tool guide 14 is relatively far from the patient and the practitioner applies a significant force to the tool guide 14, the robotic arm 13 is displaced rapidly, smoothly, and responsively. On the other hand, when the practitioner applies a low amplitude force to the tool guide 14 because the tool guide 14 is close to the relevant portion of the patient's anatomy, the robotic arm 13 is displaced at a slower speed to ensure precision and safety.

[0076] However, when the tool guide 14 is relatively close to the relevant part of the patient's anatomy, the movement of the tool guide 14 needs to be controlled with precision and at a slow speed in order to accurately reach the insertion position 102 of the medical instrument. It is therefore necessary to avoid jerky movements of the robot arm 13 caused by trembling by the practitioner. For this purpose, the value of the gain factor is defined to vary according to the force exerted on the tool guide by the practitioner. For example, the gain factor is determined so that this force reaches a minimum value F min and the maximum value F max The value of the gain factor G(f) can be defined as follows:

number

[0077] The variation of the gain factor according to the force exerted by the practitioner on the tool guide makes it possible to avoid jerks in the displacement of the robot arm 13 caused by tremors by the practitioner (tremors correspond to low amplitude forces that vary with high frequency). The variability of the gain factor according to the force exerted by the practitioner on the tool guide makes it possible to guarantee precision and safety in the displacement of the tool guide 14 when it is close to the relevant part of the patient's anatomy. Furthermore, this type of definition of the gain factor makes it possible to ensure that the force exerted by the practitioner on the tool guide F min and F max This allows for continuity of the speed of displacement of the tool guide 14 when changing between

[0078] As an alternative to what was explained with reference to equation (2), the velocity of the displacement of the tool guide 14 can also be calculated in the following form: [Number 3] |v|=G×(|f|-F min )

[0079] Figures 8 and 9 explain this in more detail. Figure 8 shows that the force exerted by the practitioner on the tool guide, as determined by the controller, is Fmin and F max FIG. 9 corresponds to the case where the gain factor G is a constant when it varies between |f| and |v|. FIG. 9 corresponds to the case where the gain factor varies according to the determined force (G is defined as in equation (1)). Each of FIGS. 8 and 9 includes four graphs. The graph in part a) of FIG. 8 and FIG. 9 represents the velocity (|v|) of the displacement of the tool guide 14 according to the determined force (|f|). The graph in part b) of FIG. 8 and FIG. 9 represents the acceleration (|a|) experienced by the tool guide 14 according to the determined force (|f|). The graph in part c) of FIG. 8 and FIG. 9 represents the determined force (|f|) over time (t) when the practitioner displaces the tool guide 14 with a low-amplitude force (slow movement due to tremor) that varies at a high frequency. The graph in part (d) of FIG. 8 and FIG. 9 represents the acceleration (|a|) experienced by the tool guide 14 over time (t) when the determined force varies as shown in the graph in part c) (slow movement due to tremor).

[0080] In the scenario corresponding to Figure 8, the force to be determined is F min and F max The gain factor G is constant when the force to be determined varies between F min The gain factor G is zero when the force F is smaller than the displacement velocity of the tool guide 14. max When it is larger than maxに As shown in part a) of Figure 8, |f| min and F max When |v| changes between zero and V max It varies linearly between |f| and F min is zero when |v| is smaller than F, as shown in part a) of Figure 8. min and F max When |f| changes between F, the acceleration |a| experienced by the tool guide 14 takes a constant value A. min is less than or F max When |f| is greater than F, the acceleration |a| experienced by the tool guide 14 is zero. Therefore, in part d) of FIG. minWhen vibrating around |a| (a low amplitude force exerted by a trembling practitioner, as shown in part c of Figure 8), the acceleration |a| experienced by the tool guide 14 is determined by the force |f| being F min It can be seen that every time |a| is exceeded, the acceleration |a| experienced by the tool guide 14 suddenly changes from a value of zero to a value of A. Conversely, the acceleration |a| is increased by the force |f| determined by F min , suddenly going from value A to value zero. This type of situation can lead to jerky movement of the tool guide 14.

[0081] In the scenario corresponding to Figure 9, the gain factor G is determined by the force |f| being F min and F max When the force F is changed between |f| and |f|, it changes linearly with |f|. min The gain factor G is zero when the force F is smaller than the displacement velocity of the tool guide 14. max When it is larger than maxに As shown in part a) of Figure 9, |f| has a set upper limit. min and F max When |v| changes between zero and V max It changes exponentially between |f| and F min is zero when |f| is below F, as shown in part a) of Figure 9. min and F max When the acceleration |a| changes between min and maximum value A max It varies linearly between |f| and F min or F max When |f| is greater than F, the acceleration |a| experienced by the tool guide 14 is zero. Therefore, from part d) of FIG. 9, it can be seen that |f| min When vibrating around |a| (a low amplitude force exerted by a trembling practitioner, as shown in part c of Figure 9), the acceleration |a| experienced by the tool guide 14 is determined by the force |f| being F min Each time it exceeds the value, it goes from zero to A min and |a| is |f| is F min, the force |f| varies continuously and linearly with |f|, and |a| is determined when the force |f| min Each time it falls below the value A min However, the value A min is significantly smaller than the value A. The change in acceleration |a| experienced by the tool guide 14, represented in part d) of Fig. 9, is clearly smaller than the change represented in part d) of Fig. 8. Varying the value of the gain factor G according to the determined force therefore makes it possible to avoid jerks in the displacement of the robot arm 13 caused by trembling by the practitioner.

[0082] It should be noted that the definition of the gain factor G proposed by equation [1] is only a non-limiting example. It will be recognized that different definitions of the gain factor G may be envisioned, varying according to the forces to be determined. The choice of a particular definition of the gain factor G is merely a variation of the present invention.

[0083] For position control, the velocity calculated at the output of the PID compensator is multiplied by a selection matrix that makes it possible to select the position direction that needs to be controlled by using a multiplicative coefficient equal to zero for the prohibited directions and one for the allowed directions. The velocity obtained after using the selection matrix corresponds to the velocity of the displacement of the tool guide 14.

[0084] As already mentioned, in the "coordinated manual control" mode, it may be advantageous to configure the control device 12 to control the robot arm 13 to prevent displacement of the tool guide 14 in at least one direction or to limit displacement of the tool guide 14 according to a single direction corresponding to the main axis 145 of the tool guide 14, in particular for releasing the tool guide 14 at the release position 103 ("release coordinated manual control" mode) or for bringing the tool guide 14 from the release position 103 to the insertion position 102 ("return coordinated manual control" mode).

[0085] Also, as already mentioned with respect to the "return coordinated manual control" mode, it may be advantageous to configure the control device 12 to control the speed of displacement of the tool guide 14 according to the distance between the current position of the tool guide 14 and the target position that the tool guide 14 needs to reach. The speed of displacement of the tool guide 14 may be controlled in particular so that the shorter this distance is (i.e., the closer the tool guide 14 is to its target position), the slower the speed of displacement becomes until it reaches zero speed when reaching the target position.

[0086] In the "approach coordinated manual control" mode, there is no position control: the displacement of the tool guide 14 is not constrained in any direction. In this mode, only force control is used.

[0087] The control device 12 of the medical robot 10 may also be configured to detect situations where there is a risk of injury from the medical instrument 15, for example when the patient 20 makes an unexpected movement while the medical instrument 15 has not yet been released from the tool guide. Indeed, this type of situation may lead to injury of the patient from the medical instrument (e.g., damage by the medical instrument to the relevant part of the anatomical structure or to healthy tissue in another part of the patient's body). Therefore, when this type of situation is detected, measures may be taken to prevent the patient from being harmed.

[0088] In certain embodiments, the tool guide 14 of the medical robot 10 includes an actuator that allows for momentary release of the medical instrument 15. The actuator is controlled by the medical robot's controller 12 to move the two moving parts of the holding device 146 apart, thus releasing the medical instrument 15. The controller 12 is configured to issue a command to the tool guide 14 to release the medical instrument 15 when a certain situation with a risk of injury is detected.

[0089] According to a first example, a particular situation at risk of injury is detected when the control device 12 receives information obtained from the navigation system 30 indicating an unexpected displacement of the patient fiducial 22 (a change in the position of the patient fiducial 22 representing an unexpected movement by the patient 20).

[0090] According to a second example, a "medical instrument insertion" mode can be selected by the user interface and activated by the control pedal 19. In this mode, the control device 12 is configured to prevent any displacement of the tool guide 14, and the control device 12 is configured to determine the force exerted on the medical instrument 15 using the force sensor. A particular situation with a risk of injury is detected, for example, when the force exerted on the medical instrument exceeds a predetermined threshold (with the result that an unexpected movement by the patient 20 exerts a force on the force sensor 16 via the medical instrument 15). According to another example, a particular situation with a risk of injury is detected when the change in the force exerted on the medical instrument exceeds a predetermined threshold over a given period of time.

[0091] The automatic release of the medical instrument 15 may be accompanied by an automatic release of the robot arm 13 in the release direction (direction along the main axis 145 of the tool guide 14 towards the base 11 of the medical robot).

[0092] The above description clearly illustrates that the present invention achieves the stated goals by virtue of its different characteristics and their advantages.

[0093] In particular, defining the rate of displacement of the tool guide 14 based on a gain factor that varies according to the force applied by the practitioner allows for controlled, precise, and smooth displacement of the robot arm 13 when the practitioner manually displaces the tool guide 14 by applying a low amplitude force. The displacement of the robot arm 13 remains smooth and responsive when the practitioner applies a high amplitude force to the tool guide 14.

[0094] The force and position control of the robotic arm 13 allows for the safe release of the tool guide 14 after (optionally partial) insertion of the medical instrument 15. If necessary, the present invention also allows for the tool guide 14 to be safely and accurately brought to the insertion position.

[0095] Finally, the automatic emergency release of the medical instrument 15 makes it possible to avoid injuring the patient when the patient makes unexpected movements during the medical procedure.

[0096] It should be noted that the present invention has been described using an optical navigation system. However, in a variant, nothing prevents the use of an electromagnetic navigation system instead of an optical navigation system. In this case, the different "markers" that can be detected by the navigation system (the markers present on the patient fiducial 22, the markers present on the tool guide 14) correspond to electromagnetic sensors, and their positions can be determined by the navigation system in the generated electromagnetic field.

Claims

1. 1. A medical robot (10) for assisting a practitioner during a medical procedure on a relevant part of the anatomical structure of a patient (20), said medical robot (10) comprising: a robot arm (13) including at its distal end a tool guide (14) designed to guide a medical instrument (15); and a control device (12) configured to control the displacement of said robot arm (13), said tool guide (14) being coupled to a force sensor (16); and when said medical robot (10) is used in a "cooperative manual control" mode, said control device (12) is configured to: Using the force sensor (16), determining the force exerted by the practitioner on the tool guide (14); calculating a velocity of displacement of said tool guide (14) according to a gain factor applied to said force so determined; Controlling the displacement of the robot arm (13) according to the velocity thus calculated. A medical robot configured as follows: The medical robot (10) is characterized in that the value of the gain factor is variable and is calculated such that the value of the gain factor increases as the force applied to the tool guide by the practitioner increases.

2. 2. The medical robot (10) of claim 1, wherein a "proportional, integral, derivative" compensator implemented by the control device (12) is configured to input the force applied to the tool guide by the practitioner and output a velocity of displacement of the tool guide (14), and the gain coefficient corresponds to a proportional parameter of the "proportional, integral, derivative" compensator.

3. The medical robot (10) of claim 1 or 2, wherein the control device (12) is also configured to prevent the displacement of the tool guide (14) in at least one direction.

4. The medical robot (10) of any one of claims 1 to 3, wherein the control device (12) is also configured to limit the displacement of the tool guide (14) in a single direction corresponding to a major axis (145) of the tool guide (14).

5. The value of the gain factor is [Equation 1] where G(f) is the gain factor, K is a constant, |f| is the force exerted by the practitioner on the tool guide (14) as determined by the controller (12) using the force sensor (16), and F ｍｉｎ and F ｍａｘ correspond to the minimum and maximum values ​​of the force exerted by the practitioner, respectively, and G(f) is zero when |f| is less than F min , and G(f) is set to a constant value when |f| is greater than F max ). The medical robot according to any one of claims 1 to 4, defined by:

6. The medical robot (10) of any one of claims 1 to 5, wherein the control device (12) is configured to calculate the speed of the displacement of the tool guide (14) according to a distance between a current position of the tool guide (14) and a target position that the tool guide needs to reach, and the shorter the distance, the lower the speed of the displacement of the tool guide (14).

7. The medical robot (10) according to any one of claims 1 to 6, wherein the robot arm (13) is an articulated arm with at least six degrees of freedom.

8. 8. The medical robot (10) of claim 1, wherein when the medical robot (10) is used in a "medical instrument insertion" mode, the control device (12) is configured to prevent any displacement of the tool guide (14), and the control device (12) is configured to determine, using the force sensor (16), the force exerted on the medical instrument (15), the tool guide (14) includes means for automatically releasing the medical instrument (15) on command from the control device (12), and the control device (12) is configured to issue a command to the tool guide (14) to release the medical instrument (15) when the force exerted on the medical instrument (15) is greater than a predetermined threshold or when a change in the force exerted on the medical instrument (15) over a given period of time is greater than a predetermined threshold.

9. The tool guide (14) includes at least one marker (147) that can be detected by a navigation system (30), and the control device (12) receiving first information from the navigation system (30) relating to a position of the tool guide (14) relative to a reference of the navigation system (30); receiving second information from the navigation system (30) regarding a target position that the tool guide (14) needs to reach, in the reference of the navigation system (30); determining the target position relative to the reference of the medical robot (10) using the second information; In "automatic control" mode, the robot arm (13) is displaced to move the tool guide (14) to the target position without the intervention of the practitioner. The medical robot (10) according to any one of claims 1 to 8, configured to:

10. 10. The medical robot (10) of claim 9, wherein the second information corresponds to a position of a patient fiducial (22) in the fiducial of the navigation system (30) that is designed to be positioned near the relevant portion of the anatomical structure in the patient (20), the patient fiducial (22) including at least one marker (23) that can be detected by the navigation system (30) and at least one radiopaque marker (24), and the control device (12) is configured to determine the target position of the tool guide (14) from the position of the patient fiducial (22) and from a trajectory that the medical instrument (15) needs to follow to perform a medical intervention, the trajectory being defined with respect to the position of the patient fiducial (22) using a pre-intervention medical image (40) in which the relevant portion of the anatomical structure of the patient and the at least one radiopaque marker (24) of the patient fiducial (22) are visible.

11. The control device (12) storing the position of the tool guide (14) at a first instant relative to the position of the patient reference (22) as a reference position; determining whether the difference between the position of the tool guide (14) at the second instant and the reference position is below a predetermined threshold; The medical robot (10) according to claim 10, configured to:

12. 12. The medical robot (10) of claim 10 or 11, wherein the tool guide (14) includes means for automatically releasing the medical instrument (15) upon command from the control device (12), and the control device (12) is configured to issue a command to the tool guide (14) to release the medical instrument (15) when the control device (12) receives information from the navigation system (30) indicating an unexpected displacement of the patient reference (22).

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