Collaborative medical robot for guiding instrument insertion

Abstract

The invention relates to a medical robot (10) for assisting a practitioner in performing a minimally invasive medical procedure. The medical robot comprises a robotic arm (13) equipped with a tool guide (14) for guiding the insertion of a medical instrument (15) into the body of a patient (20) according to a planned trajectory. A control unit (12) of the medical robot is configured to perform a sequence of movements of the robotic arm (13) successively comprising an automatic movement to move the tool guide to an offset pose (102), and a cooperative manual movement to move the tool guide from the offset pose to an insertion pose (103). The offset pose lies in a plane orthogonal to the planned trajectory and passing through the insertion pose. The only possible movements of the tool guide during the cooperative manual movement are in this plane. This sequence of movements makes it possible to reposition the tool guide, precisely and safely, so as to take back hold of a medical instrument already partially inserted into the body of the patient.

Description

[0001] Collaborative medical robot to guide instrument insertion

[0002] Field of invention

[0003] The present invention belongs to the field of robotic devices for assisting a practitioner during a medical procedure. In particular, the invention relates to a collaborative medical robot for guiding the insertion of a medical instrument during a minimally invasive medical procedure.

[0004] State of the art

[0005] Minimally invasive or percutaneous medical procedures may require a practitioner to insert one or more medical instruments (e.g., a needle, probe, catheter, etc.) into a patient's body to a certain depth to reach a target anatomical area (e.g., a tumor in the liver, lung, kidney, or bone).

[0006] In order to improve the precision of the insertion gesture and limit the radiation doses on the patient, it is possible to use automatically controlled robotic arms. The robotic arm can be equipped with a tool guide to guide a medical instrument. The practitioner indicates, for example, on a pre-interventional medical image a trajectory that the medical instrument must follow to reach a target area of ​​the patient's anatomy of interest, and the robotic arm automatically moves into a position such that the tool guide allows the medical instrument to be guided according to the planned trajectory.

[0007] In order to check that the medical instrument follows the planned trajectory, it may be necessary to acquire one or more control medical images during insertion. Indeed, the trajectory of the medical instrument may be deviated when it pierces the patient's skin at the entry point or the surface of one of the organs (for example, the liver capsule) or when it crosses the cortical bone.

[0008] When the medical instrument is inserted, it is held by the tool guide. To acquire the control medical images, it is necessary to release the medical instrument from the guide. After acquiring the control images, in the case where the instrument follows the trajectory as planned, or in the case where the deviation of the instrument from the planned trajectory can be corrected by slightly modifying the planned trajectory, the insertion can be continued, which requires repositioning the medical instrument in the tool guide. To perform this repositioning, it is possible to send the robotic arm automatically to the insertion position while manually moving the medical instrument away to avoid a collision between the tool guide and the medical instrument. This solution is not optimal because it can cause the medical instrument to deviate from the planned trajectory.

[0009] Another solution could be to use a free manual movement mode of the robotic arm to reposition the medical instrument in the tool guide. This solution is not optimal either because it requires great ease (transparency) in the manual movement of the robotic arm (in particular to adjust the orientation of the tool guide) and it does not guarantee sufficient precision in the positioning of the tool guide.

[0010] Patent application FR3120777A1 describes various modes of control of a robotic arm, including a cooperative manual control mode for disengaging and returning the tool guide to a predetermined insertion position. In this control mode, it is necessary for the patient to be returned exactly to the position in which they were relative to the robot before the tool guide was disengaged. If the robot or the patient moves between the disengagement and repositioning of the tool guide, it is not possible to return the guide to a correct insertion position relative to the patient. Furthermore, it is also not possible to replan a new path in the event of a deviation from the trajectory.

[0011] Statement of the invention

[0012] The solution presented in the present application aims to remedy all or part of the drawbacks of the prior art, in particular those set out above.

[0013] For this purpose, and according to a first aspect, a medical robot is proposed for assisting a practitioner during a minimally invasive medical intervention on an anatomy of interest of a patient. The medical robot comprises a robotic arm, a distal end of which is equipped with a tool guide intended to guide the insertion of at least part of a medical instrument into the patient's body according to a planned trajectory. The tool guide is coupled to a force sensor. The medical robot comprises a control unit configured to control the robotic arm in order to move the tool guide. The control unit is configured to determine, from the planned trajectory, an insertion pose and an offset pose of the tool guide, the offset pose being in a plane orthogonal to the planned trajectory and passing through the insertion pose, and to perform a sequence of movements of the robotic arm successively comprising:

[0014] - an automatic movement to move the tool guide to the offset position,

[0015] - a cooperative manual movement to move the tool guide from the offset position to the insertion position. The cooperative manual movement is controlled to constrain the movement of the tool guide on the plane orthogonal to the planned trajectory and passing through the insertion position, such that the only possible movements of the tool guide during the cooperative manual movement are in this plane. The speed of movement of the tool guide during the cooperative manual movement is determined as a function of a force exerted by the practitioner on the tool guide, said force being measured by the force sensor.

[0016] This particular sequence of movements allows the tool guide to be repositioned, precisely and safely, to regrip a medical instrument already partially inserted into the patient's body (e.g. after capturing control images). The automatic movement keeps the tool guide at a certain distance from the medical instrument, to limit the risk of collision between the tool guide and the instrument. The final approach of the tool guide to regrip the partially inserted medical instrument is ensured by the user, thanks to a cooperative manual movement mode. The positioning accuracy in orientation along the axis of the planned trajectory is guaranteed by the robot. The tool guide axis is constrained during the cooperative manual movement.

[0017] In particular embodiments, the invention may further comprise one or more of the following features, taken individually or in any technically possible combination.

[0018] In particular embodiments, the tool guide has a guide axis and a main axis orthogonal to the guide axis. The insertion position is such that, at the insertion position, the guide axis coincides with the axis of the planned trajectory. The only possible movements of the tool guide during the cooperative manual movement are a translation along the main axis of the tool guide and optionally a rotation around the axis of the planned trajectory.

[0019] In particular embodiments, the control unit is configured to determine an approach pose, and the automatic movement successively comprises:

[0020] - a free automatic movement to move the tool guide to the approach position,

[0021] - a predictable automatic movement to move the tool guide from the approach pose to the offset pose.

[0022] The decomposition of the automatic movement into a free movement and a predictable movement provides security. Due to its repeatable aspect, the user can intuit the predictable automatic movement that will be performed between the approach pose and the offset pose. At the end of the free movement (when the tool guide is at the approach pose), the practitioner can imagine the predictable movement that will follow, and if he realizes that an obstacle is preventing it, he can decide not to trigger it.

[0023] In particular embodiments, the predictable automatic motion comprises linear motion contained within a plane comprising the planned trajectory and the approach pose.

[0024] In particular embodiments, the predictable automatic motion is a linear motion parallel to the planned path.

[0025] In particular embodiments, the predictable automatic motion comprises linear motion contained in a plane orthogonal to the axis of the planned trajectory and passing through the insertion pose.

[0026] In particular embodiments, during the cooperative manual movement, the speed of movement of the tool guide is determined as a function of a gain factor applied to the force exerted by the practitioner, and the gain factor is also calculated as a function of the force exerted by the practitioner.

[0027] In particular embodiments, the value of the gain factor is calculated as follows: where G(f) is the gain factor, K is a constant, |f| is the force exerted by the practitioner on the tool guide, Emin and E max correspond respectively to a minimum value and a maximum value for the effort exerted by the practitioner.

[0028] In particular embodiments, the speed of movement of the tool guide is determined based on a distance between a current pose of the tool guide and the insertion pose.

[0029] In particular embodiments, the control unit is configured to prohibit any movement of the tool guide for at least a predetermined duration when the insertion position is reached.

[0030] In particular embodiments, the robotic arm is an articulated arm having at least six degrees of freedom.

[0031] In particular embodiments, the insertion pose and / or the planned trajectory is determined from a control medical image on which the partially inserted medical instrument 15 is visible.

[0032] In particular embodiments, the medical robot includes a user interface configured to provide information indicating whether the tool guide is correctly positioned to follow the planned trajectory. In particular embodiments, the medical robot includes a user interface configured to provide information indicating which motion, from a set of predefined motions, is currently in progress or ready to be triggered by a user command. The set of predefined motions includes free automatic motion, predictable automatic motion, and cooperative manual motion.

[0033] Presentation of figures

[0034] The invention will be better understood by reading the following description, given by way of non-limiting example, and made with reference to figures 1 to 14 which represent:

[0035] [Fig. 1] a schematic representation of an exemplary embodiment of a medical robot according to the invention,

[0036] [Fig. 2] a schematic representation of a path to be followed by a medical instrument from an entry point at the patient's skin to a target point in or near a region to be treated in the patient's anatomy of interest,

[0037] [Fig. 3] a schematic representation of an exemplary embodiment of a robotic arm, [Fig. 4] a schematic representation of an exemplary embodiment of a tool guide intended to be fixed to a distal end of the robotic arm,

[0038] [Fig. 5] an illustration of the tool guide showing a device for holding a medical instrument at one end of the tool guide,

[0039] [Fig. 6] an illustration of the tool guide highlighting the positioning of the medical instrument on the tool guide as well as markers detectable by a navigation system,

[0040] [Fig. 7] an illustration of an example of the implementation of the tool guide holding system,

[0041] [Fig. 8] a schematic representation of the holding system in a closed position,

[0042] [Fig. 9] a schematic representation of the holding system in an open position,

[0043] [Fig. 10] an illustration of the determination of an insertion pose, an offset pose and an approach pose for the tool guide,

[0044] [Fig. 1 1] an illustration of the medical robot with the tool guide at the approach pose,

[0045] [Fig. 12] an illustration of the medical robot with the tool guide in the remote position,

[0046] [Fig. 13] an illustration of the medical robot with the tool guide at the insertion position,

[0047] [Fig. 14] an example of implementation of a servo loop for admittance control of the cooperative manual movement of the tool guide.

[0048] In these figures, identical references from one figure to another designate identical or similar elements. For reasons of clarity, the elements represented are not necessarily to the same scale, unless otherwise indicated.

[0049] Detailed description of the invention

[0050] Figure 1 schematically represents an exemplary embodiment of a medical robot 10. The medical robot 10 is used to assist a practitioner during a minimally invasive medical intervention on an anatomy of interest of a patient 20 positioned on an intervention table 21. This type of intervention generally requires the insertion by the practitioner of one or more medical instruments 15 into the body of the patient 20.

[0051] As illustrated in Figure 2, the medical instrument 15 is inserted into the body of the patient 20 following a rectilinear trajectory 41 from an entry point 43, located at the level of the patient's skin, to a certain depth to reach a target point 44 in or near a region to be treated of the anatomy of interest 45.

[0052] The intervention may in particular aim to perform the ablation or biopsy of a tumor in an organ or in a bone, to treat a bone pathology (for example by vertebroplasty or cementoplasty), or to stimulate a particular anatomical zone. The anatomy of interest may correspond to an organ (for example the liver, a lung, a kidney or the brain) or to a bone (for example a vertebra, a tibia, a femur, a hip, a pelvic bone, the pelvis, etc.). The medical instrument 15 may be a needle, an electrode, a probe, a drill, a trocar, a screw, etc.

[0053] In the example considered and illustrated in Figure 1, the medical robot 10 comprises a base 11. The base 11 of the medical robot 10 is equipped with motorized wheels, which allows the medical robot 10 to move in different directions by translational and / or rotational movements. The medical robot 10 further comprises a robotic arm 13, one end of which is connected to the base 11. At the other end of the robotic arm 13 is fixed a tool guide 14 for guiding the medical instrument 15. The medical robot 10 is thus used to position, hold and guide the medical instrument 15; it plays the role of a third hand for the practitioner.

[0054] As illustrated in Figure 1, the medical robot 10 comprises a control unit 12 configured to control the movement of the robotic arm 13 (and therefore of the tool guide 14 carried by the robotic arm 13). The control unit 12 comprises at least one processor 122 and at least one 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 to be executed to implement the control of the robotic arm 13.

[0055] In the example considered, and as illustrated in Figure 3, the robotic arm 13 comprises six rotoid joints 131 to 136 providing six degrees of freedom allowing the medical instrument 15 to be positioned and / or moved in any pose of the three-dimensional space. The rotoid joint 136 corresponds to a rotation around a main axis of the tool guide 14. Each joint comprises an encoder allowing its angular position to be known in real time. Advantageously, the joints of the robotic arm are not aligned and have an offset relative to each other, which allows better accessibility (a greater number of possible configurations of the robotic arm 13).

[0056] When the medical instrument 15 has axial symmetry for the part of the instrument that is intended to penetrate the patient's body (this is the case, for example, for a needle), five degrees of freedom are sufficient to guide and insert the medical instrument. The additional degree of freedom allows for a situation of redundancy and to have an infinite number of possible configurations of the robotic arm allowing the tool guide to guide the medical instrument 15 along the desired trajectory 41. This situation of redundancy is particularly useful for adapting to the external envelope of the patient or for ensuring the visibility of markers cooperating with a navigation system.

[0057] Figures 4 to 6 represent an exemplary embodiment of the tool guide 14. In the example considered, and as illustrated in Figure 4, the tool guide 14 is fixed to the robotic arm 13 by means of a flange 17. The tool guide 14 is coupled to a force sensor 16 to allow the control unit 12 to determine a force exerted on the tool guide 14. This force can in particular be exerted by the practitioner when he manually moves the robotic arm 13. The term “practitioner” must be interpreted in the broad sense: the medical robot can be manipulated by a surgeon, or by a medical operator who acts under the supervision of a surgeon.

[0058] As illustrated in Figures 5 and 6, the tool guide 14 comprises a body 141 with a base 142 intended to be fixed to the flange 17 using screws 143, as well as a holding system 50 comprising two parts movable relative to each other. These two movable parts form a clamp allowing the holding system 50 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 holding system 50 can be actuated by a drive system such as a gear, a cam, a screw with reverse threads and / or a linear actuator, in order to lock or release the medical instrument 15. The tool guide 14 makes it possible, for example, to guide medical instruments of different diameters. For example, such a guide can guide medical instruments with a diameter between 8 and 21 gauges (8 gauges correspond to an external diameter of 4.191 mm; 21 gauges correspond to an external diameter of 0.812 mm). The holding system 50 defines a guide axis XX' orthogonal to a main axis ZZ' of the tool guide 14 (the main axis of the tool guide is in the direction going from the base towards the holding system 50).

[0059] Figures 7 to 9 illustrate an exemplary embodiment of the holding system 50 of the tool guide 14. This embodiment of the holding system is similar to that described with reference to Figures 7 and 8 of patent application FR3094627A1. In this exemplary embodiment, the holding system 50 of the tool guide 14 comprises two jaws 51, 55. The jaws 51 and 55 can be driven between a closed position (as illustrated in Figure 8) or an open position (as illustrated in Figure 9). Each jaw has a groove 52, 56. The grooves 52, 56 extend transversely relative to teeth 53, 57 arranged so as to interpenetrate when the holding system 50 is in the closed position (each tooth 53, 57 has a segment of a groove 52, 56). In the closed position, the grooves 52 and 56 are adjoining and define a guide conduit 59 for holding the medical instrument 15 and guiding it in translation.In the open position, the grooves 52 and 56 are moved away from each other to place or release the medical instrument 15. The transition from the closed position to the open position can be caused by a pressure force from the practitioner on a lever 58 formed by a bearing surface of one of the jaws (the jaw 55 in the example illustrated in Figures 11 to 13).

[0060] A navigation system (not shown in the figures) may be used to provide the control unit 12 of the medical robot 10 with information relating to a pose of the tool guide 14 or to a particular pose that the tool guide 14 must reach. In particular, an “insertion pose” is defined as the pose of the tool guide 14 at which it allows the medical instrument 15 to be guided along the desired trajectory 41 and at the exact depth to reach the target point 44 in the anatomy of interest 45. A pose of the tool guide is for example initially defined in a reference frame of the navigation system and then transformed into a pose in a reference frame of the medical robot 10 by the control unit 12.

[0061] In the present application, the term "pose" must be understood as meaning "position and orientation". The pose of an object is defined relative to a reference point corresponding to the origin of an orthonormal reference frame (the reference point defines the position of the object and the orthonormal reference frame defines the orientation of the object). The "insertion pose" corresponds to a pose of the tool guide at which the tool guide 14 has a guide duct 59 making it possible to guide the medical instrument 15 along the axis of the planned trajectory 41 and at the exact depth to reach the target point 44. In FIG. 1, the axis of the planned trajectory is represented by the axis TT'. In FIGS. 4, 5 and 7, the axis of the guide duct 59 of the tool guide 14 is represented by the axis XX'. At the insertion pose, the guide axis XX' coincides with the axis TT' of the planned trajectory.

[0062] During insertion, the medical instrument 15 is guided in translation by the guide duct until it reaches a stop position (a portion of the medical instrument then abuts against the tool guide and prevents further insertion). The insertion position is defined such that when this stop position is reached, the distal end of the medical instrument 15 is at the target point 44. In the example illustrated in FIG. 6, the tool guide 14 holds the medical instrument 15 in the holding system 50, and the medical instrument 15 is in abutment against the tool guide 14; this corresponds to the position of the medical instrument when it reaches the target point 44.

[0063] When the part of the medical instrument 15 intended to penetrate the patient's body has axial symmetry along the axis of the guide conduit, the different positions of the tool guide 14 obtained by rotation around this axis correspond to the same insertion position. In the present application, the expression "the position of the tool guide 14" must therefore be interpreted as corresponding to "the position of the guide conduit 59 of the tool guide 14".

[0064] The navigation system and the control unit 12 of the medical robot 10 can exchange data via communication means (wired or wireless). In the example considered, the navigation system is an optical navigation system (for example an infrared stereoscopic camera). As illustrated in FIGS. 5 and 6, the tool guide 14 comprises pads 144 intended to receive optical markers 147. All of the optical markers 147 present on the tool guide 14 correspond to a robot reference. The use of at least three optical markers makes it possible to define a plane and therefore a direct orthonormal three-dimensional reference frame. This thus makes it possible to determine the pose of the reference frame formed from the optical markers 147 which represent the tool guide 14.

[0065] As illustrated in Figure 1, a patient reference 22 is placed on the patient 20 near the anatomy of interest. In the example considered, the patient reference 22 also comprises at least three optical markers, such that the pose of the patient reference 22 can be determined in the three spatial dimensions of the reference frame of the navigation system.

[0066] The insertion position to be reached by the tool guide 14 can be defined from the position of the patient reference 22. For this purpose, the patient reference 22 also includes radiopaque markers which are visible on a medical image acquired by a medical imaging device (for example by computed tomography, magnetic resonance, ultrasound, tomography, positron emission tomography, etc.).

[0067] As illustrated in Figure 1, it is possible to plan the medical intervention from a pre-interventional medical image 40 acquired on the patient provided with the patient reference 22. This pre-interventional medical image 40 is stored in the memory 121 of the control unit 12. It is then possible for the control unit 12, from the pre-interventional medical image 40, to define the insertion position that the tool guide 14 must take to guide the medical instrument 15 to carry out the medical intervention. Planning the medical intervention includes determining, on the pre-intervention image 40, the trajectory 41 to be followed by the medical instrument 15 (e.g., a needle) between the entry point 43 located at the skin of the patient 20 and the target point 44 located in or near the region to be treated (e.g., a tumor) in the anatomy of interest 45 (e.g., the liver).

[0068] The radiopaque elements of the patient reference 22 are visible on the pre-interventional image 40. The pose of the patient reference 22 can therefore be defined in the medical image. The planned trajectory 41 is also visible on the medical image. The insertion pose of the tool guide 14 for following the trajectory 41 can then be defined relative to the pose of the patient reference 22.

[0069] Using the navigation system 30, the medical robot 10 can determine the current pose of the tool guide 14 and the pose of the patient reference 22. Thanks to the pre-intervention image 40, the medical robot 10 knows the insertion pose that the tool guide 14 must reach relative to the pose of the patient reference 22. The control unit 12 can then be configured to automatically move the robotic arm 13 so that the tool guide 14 reaches the insertion pose.

[0070] It is advantageous to check, after a partial insertion of the medical instrument, that the medical instrument follows the planned trajectory 41 (it happens that the trajectory of the medical instrument is deviated when it pierces the patient's skin at the entry point, or when it crosses a particular anatomical structure). To do this, it may be necessary to acquire one or more control medical images during insertion.

[0071] When the medical instrument 15 is inserted, it is held by the holding system 50 of the tool guide 14. To acquire the control medical images, it is therefore necessary to release the medical instrument from the guide. After acquiring the control images, it is necessary to reposition the medical instrument 15 in the holding system 50 of the tool guide 14.

[0072] To reposition the medical instrument 15 in the tool guide 14 precisely and safely, the control unit 12 is configured to determine, from the planned trajectory 41, at least two particular poses of the tool guide 14: an insertion pose and a remote pose. The control unit 12 is also configured to implement a specific sequence of movements of the robotic arm 13 comprising successively:

[0073] - an automatic movement to move the tool guide 14 to the offset position,

[0074] - a cooperative manual movement to move the tool guide 14 from the offset position to the insertion position.

[0075] Advantageously, the control unit may be configured to determine a third particular pose, namely an approach pose, and the automatic movement may successively comprise:

[0076] - a free automatic movement to move the tool guide 14 to the approach position,

[0077] - a predictable automatic movement to move the tool guide 14 from the approach position to the offset position.

[0078] Figures 10 to 13 illustrate the three particular poses (the insertion pose 103, the offset pose 102, and the approach pose 101), as well as the successive movements allowing the tool guide 14 to reach the insertion pose 103 from any initial position 100 by successively passing through the approach pose 101 and the offset pose 102.

[0079] More particularly, Figure 10 illustrates the determination of the three particular poses (the insertion pose 103, the offset pose 102, and the approach pose 101). Figure 11 illustrates the free automatic movement of the tool guide 14 from any initial position 100 to the approach pose 101. Figure 12 illustrates the predictable automatic movement of the tool guide 14 from the approach pose 101 to the offset pose 102. Figure 13 illustrates the cooperative manual movement of the tool guide 14 from the offset pose 102 to the insertion pose 103.

[0080] As indicated previously, the insertion position 103 corresponds to a position of the tool guide 14 in which the tool guide 14 has a guide conduit 59 making it possible to guide the medical instrument 15 along the axis of the planned trajectory 41 and at the exact depth to reach the target point 44 (at the insertion position, the guide axis XX' coincides with the axis TT' of the planned trajectory).

[0081] The insertion pose 103 may be exactly identical to the initial insertion pose that was used to perform the partial insertion of the medical instrument 15 before taking the control images. This is the case if it appears on the control images that the medical instrument 15 is indeed following the planned trajectory 41. The insertion pose 103 may, however, also correspond to a correction of the initial insertion pose. This is the case, for example, if it appears on the control images that the medical instrument 15 has slightly deviated from the initially planned trajectory, and that the planned trajectory should be slightly corrected to continue the intervention. The insertion pose 103 corresponds to the pose at which the tool guide 14 will re-grip the medical instrument 15 partially inserted into the patient's body.This is also the pose at which the tool guide 14 makes it possible to finalize the insertion of the medical instrument 15 up to the target point (up to the stop position). As detailed previously, the insertion pose 103 can be determined by the control unit 12 from a medical image on which the patient reference 22 is visible and on which the trajectory 41 can be defined.

[0082] The offset pose 102 can be defined from the insertion pose 103. As illustrated in FIG. 10, the offset pose 102 is located in a plane 104 orthogonal to the planned trajectory 41 and passing through the insertion pose 103. The offset pose 102 has the same orientation as the insertion pose 103 (in other words, the guide conduit 59 of the tool guide 14 is oriented along the same guide axis XX' at the insertion pose 103 and at the offset pose 102). The offset pose 102 is defined to be sufficiently far from the insertion pose 103 to avoid a collision between the tool guide 14 and the medical instrument 15 during the predictable automatic movement. The distance between the insertion position 103 and the offset position 102 is for example between 25 mm and 100 mm (between twenty-five and one hundred millimeters). In the example considered, the distance between the insertion position 103 and the offset position 102 is equal to 50 mm (fifty millimeters).

[0083] The approach pose 101 can be defined from the offset pose 102. In the example considered, and as illustrated in FIG. 10, the approach pose 101 is for example located on an axis 105 parallel to the planned trajectory 41 and passing through the offset pose 102. The approach pose 101 has the same orientation as the insertion pose 103 and the offset pose 102 (in other words the guide conduit 59 of the tool guide 14 is oriented along the same guide axis XX' at the insertion pose 103, at the offset pose 102 and at the approach pose 101). Here again, the approach pose 101 is defined to be sufficiently far from the medical instrument 15 and the patient 20 to avoid any risk of collision during the free automatic movement. The distance between the approach pose 101 and the offset pose 102 is for example between 25 mm and 100 mm. In the example considered, the distance between the approach pose 101 and the offset pose 102 is equal to 50 mm.

[0084] The expression “automatic movement” means that the movement of the robotic arm 13 is carried out autonomously by the medical robot 10, without intervention by the practitioner during the movement (possibly the practitioner can trigger the start of the movement, but he does not intervene during the movement). This is the case for the free automatic movement which makes it possible to move the tool guide 14 from any initial position 100 to the approach position 101 (see figure 11) and for the predictable automatic movement which makes it possible to move the tool guide 14 from the approach position 101 to the offset position 102 (see figure 12).

[0085] The expression "predictable movement" means that the movement is repeatable. In particular, the movement making it possible to move the tool guide 14 from the approach pose 101 to the offset pose 102 (as in FIG. 12) is always the same relative to these two poses. On the contrary, the movement making it possible to move the tool guide 14 from any initial pose 100 to the approach pose 101 (as in FIG. 11) is not necessarily predictable (it may consist of one or more elementary movements between the initial pose 100 and the approach pose 101 which may vary from one time to the next relative to these two poses).

[0086] By its repeatable aspect, the user can intuit the predictable automatic movement that will be carried out between the approach pose 101 and the offset pose 102. At the end of the free movement (when the tool guide is at the approach pose 101), the practitioner can imagine the predictable movement that will follow, and if he realizes that an obstacle is preventing it, he can decide not to trigger it.

[0087] Advantageously, the predictable automatic movement can be defined such that the orientation of the guide axis XX' of the tool guide 14 is maintained throughout the movement of the tool guide 14 between the approach pose 101 and the offset pose 102.

[0088] The predictable automatic movement comprises, for example, a linear movement contained in a plane comprising the planned trajectory 41 and the approach pose 101. In the example considered and illustrated in FIG. 12, the predictable automatic movement is a linear movement parallel to the planned trajectory 41. During this movement, the guide axis XX' of the tool guide 14 remains parallel to the axis TT' of the planned trajectory 41. In this case, this corresponds to an approach "from above". Alternatively or in addition, the predictable automatic movement may comprise a linear movement contained in a plane orthogonal to the axis TT' of the planned trajectory 41, and passing through the insertion pose 103. In this case, this corresponds to an approach "from the side".

[0089] The cooperative manual movement for moving the tool guide 14 from the remote position 102 to the insertion position 103 (see Figure 13) is not an automatic movement. This movement is not implemented entirely autonomously by the medical robot 10. This movement requires collaboration between the medical robot 10 and the practitioner.

[0090] In particular, the speed of movement of the tool guide 14 during the cooperative manual movement is controlled by the control unit 12 as a function of a force exerted by the practitioner on the tool guide 14. The force exerted by the practitioner is measured by the force sensor 16 (it corresponds to the resultant of the forces and torques applied to the tool guide 14).

[0091] Furthermore, the cooperative manual movement is controlled to constrain the movement of the tool guide 14 on a plane 104 orthogonal to the planned trajectory 41 and passing through the insertion pose 103 (see figures 10 and 13). The only movements authorized for the tool guide 14 during the cooperative manual movement are for example a translation along the main axis ZZ' of the tool guide 14 and optionally a rotation around the axis TT' of the planned trajectory 41 (in a first exemplary embodiment, only the translation is authorized; in another exemplary embodiment, only the translation and the rotation are authorized).

[0092] Rotation around the TT' axis of the planned trajectory 41 may allow collision avoidance, optimization of the visibility of the tool guide markers 14 for the navigation system, or satisfaction of any other criteria at the discretion of the practitioner during cooperative manual movement.

[0093] Figure 14 schematically represents an example of implementation of a servo loop for admittance control of the cooperative manual movement of the tool guide 14.

[0094] In the example considered and illustrated in Figure 14, the force measured by the force sensor 16 and the position of the tool guide 14 are input data of the control loop. The control loop is for example clocked at a frequency of 125 Hz. The control loop provides as output a Cartesian speed V4= [v x v y v z w x w y w z] of movement of the tool guide 14. This control loop comprises the calculation of a speed V4 corresponding to free cooperative manual guidance, to which constraints are applied (in particular a speed control, a selection of authorized directions and a haptic law) to achieve the speed V4 to be applied to the tool guide to obtain a controlled cooperative manual movement in the plane 104 orthogonal to the planned trajectory 41.

[0095] To obtain free cooperative manual guidance that would allow free movement in the six dimensions of space, the algorithm calculates a speed of movement of the robotic arm allowing the force felt by the force sensor 16 to be canceled. In other words, the difference (also called error) between the value of the force at a current instant (i.e. the force measured by the force sensor 16 at each iteration of the control loop) and the value of the desired force must tend towards zero. The objective of the algorithm is to calculate a speed V4 making the error tend towards zero. For this, a PID corrector (“Proportional, Integral, Derivative”) is used. The error (i.e. the difference between the current force and the desired force) is the input data of the PID corrector which gives as output a speed V4 of the robotic arm 13 allowing to have a force error that tends towards zero.

[0096] The speed of movement of the tool guide 14 is determined as a function of a gain factor applied to the force measured by the force sensor 16. When the practitioner exerts low amplitude forces, jerky movements (tremors) are produced. To prevent the robotic arm 13 from reproducing these jerky movements, it is advantageous for the gain factor to also be calculated as a function of the force exerted by the practitioner. For this, the PID corrector has a constant proportional component as well as a variable proportional component. The values ​​of these two components are determined by a person skilled in the art and as a function of the equipment. The variable component varies proportionally as a function of the force exerted by the practitioner on the robotic arm within a certain range of values ​​and as a function of the constant proportional component.The forces due to the variable noise of the force sensor depending on its current pose are not considered because taking these forces into account would lead to moving the robot even when no force is actually exerted by the practitioner. The value of the gain factor is for example calculated as follows: [Math.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), Emin and E ma x correspond respectively to a minimum value and a maximum value for the effort exerted by the practitioner.

[0097] The value of the speed V4 obtained at the output of the PID corrector is then multiplied by a selection matrix. This selection matrix makes it possible to select the authorized directions and the prohibited directions during the movement. As a reminder, the only movements authorized for the tool guide 14 during the cooperative manual movement are a translation along the main axis ZZ' of the tool guide 14 and optionally a rotation around the axis TT' of the planned trajectory 41. We then obtain a speed y2 = [0 0 v z w x 0 0]

[0098] The speed V2 corresponds to a speed at the position of the insertion pose = [w x w y w z ] T is the rotation component of the speed at the insertion position 103). It is appropriate to transfer the speed V2 to the tool guide 14, using a transfer matrix, according to the following formula:

[0099] [Math. 2] where I3 is the identity matrix of size 3x3, and d x is the position of the insertion pose 103 expressed in the frame of reference of the tool guide 14. This product makes it possible to calculate the linear speed of the tool guide 14 due to the rotation around the insertion pose which keeps the main axis ZZ' of the tool guide 14 aligned with the insertion pose.

[0100] Haptic behavior rules can then be applied to the obtained speed V3. In particular, it is advantageous if the movement speed of the tool guide 14 is determined as a function of a distance between the current pose of the tool guide 14 and the insertion pose 103.

[0101] For example, for a constant effort from the practitioner, when the distance between the current position of the tool guide 14 and the insertion position 103 is less than a threshold, it is possible to consider decreasing the gain factor proportionally with the distance.

[0102] According to another example, when the distance between the current pose of the tool guide 14 and the insertion pose 103 is less than a threshold, an attractive spring behavior can be simulated by forcing the speed to be proportional to the distance, independently of the effort exerted by the practitioner. For example, when the distance d z between the current position of the tool guide 14 and the insertion position 103 is less than 5 mm, the component v z of the speed V3 can be defined by the formula: [Math. 3]

[0103] According to another example, when the distance between the current pose of the tool guide and the insertion pose is less than a threshold, the speed becomes constant (independently of the effort exerted by the practitioner, and independently of the distance between the current pose of the tool guide and the insertion pose).

[0104] It is also possible to configure the control unit 12 to prohibit any movement of the tool guide 14 for at least a predetermined duration when the insertion position 103 is reached (i.e. when the distance between the current position of the tool guide 14 and the insertion position 103 is sufficiently small to consider that the insertion position 103 is reached).

[0105] One or more of the rules cited above may be used to provide one or more haptic indications allowing the practitioner to feel the approach and the reaching of the insertion pose 103. In particular, the fact of prohibiting any movement of the tool guide 14 for at least a predetermined duration when the insertion pose 103 is reached provides the practitioner with a “virtual notch” effect.

[0106] The various movements of the robot arm 13 can be conditioned by the selection of a particular control mode on a user interface (for example on a touch display screen of the medical robot 10) and by the activation of the selected mode using a control pedal 19.

[0107] The control unit 12 may optionally be configured to automatically switch from one control mode to another, at the end of a particular movement (for example, automatic switch to “predictable automatic mode” at the end of the “free automatic mode”, or automatic switch to “cooperative manual mode” at the end of the “predictable automatic mode”). In this case, the user may simply activate the different movements successively using the pedal 19. The control unit 12 may be configured to automatically exit the “cooperative manual mode” when the insertion position 103 is reached by the tool guide 14.

[0108] The control unit 12 may be configured to display (for example on a touch display screen of the medical robot 10 or on an augmented reality headset connected to the medical robot 10) information on the pose of the tool guide 14. In particular, the displayed information may indicate whether the pose of the tool guide 14 cannot be verified (for example if one or more optical markers 147 of the tool guide 14 are not visible by the navigation system). The displayed information may also indicate whether the tool guide has reached a particular pose (approach pose 101, offset pose 102 or insertion pose 103).

[0109] When the tool guide 14 has reached the insertion position 103, the practitioner can finalize the insertion of the medical instrument 15 into the anatomy of interest.

[0110] An example of implementation of the medical robot 10 will now be described. Firstly, at the command of the practitioner, the control unit 12 of the medical robot 10 implements a movement of the robotic arm 13 to automatically position the tool guide 14 at an initial insertion position. The initial insertion position corresponds to a position of the tool guide 14 at which the tool guide 14 has a guide conduit 59 making it possible to guide the medical instrument 15 along an initial trajectory planned on a pre-interventional medical image. The practitioner can then place the medical instrument 15 in the tool guide 14 and proceed with a partial insertion of the medical instrument 15 into the patient's body.

[0111] In a second step, the practitioner opens the clamp of the tool guide 14 to release the medical instrument 15. At the command of the practitioner, the medical robot 10 switches to a cooperative manual release control mode to move the tool guide 14 away from the medical instrument.

[0112] In a third step, one or more medical control images are produced to verify that the partially inserted medical instrument 15 has not deviated from the planned trajectory. The operating table on which the patient is positioned may possibly be moved to produce these control images, then replaced in the working area of ​​the medical robot 10.

[0113] If necessary, the planned insertion pose and / or trajectory can be corrected from the control images (i.e., a new insertion pose different from the initial insertion pose and / or a new trajectory different from the initial trajectory can be determined). The actual position of the partially inserted medical instrument can be taken into account for the calculation of the insertion pose, which allows the medical instrument to be precisely recaptured after a possible update of the planning data using the control images.

[0114] This makes it easier to produce the control image and allows for early detection and correction of any deviation of the medical instrument.

[0115] In a fourth step, the robotic arm 13 is controlled to move the tool guide 14 according to the particular sequence of movements proposed by the invention. This particular sequence of movements allows the tool guide 14 to re-grip the partially inserted medical instrument 15 with precision and safety. The sequence of movements successively comprises a free automatic movement to move the tool guide 14 to the approach pose 101, a predictable automatic movement to move the tool guide 14 from the approach pose 101 to the offset pose 102, and a cooperative manual movement to move the tool guide 14 from the offset pose 102 to the insertion pose 103.

[0116] During the cooperative manual movement, the movement of the tool guide 14 is constrained on a plane orthogonal to the axis of the medical instrument 15 and the main axis ZZ' of the tool guide 14 is constrained in the direction of the medical instrument (it is only possible to move closer to or further from the medical instrument and to rotate around it). When the tool guide 14 is at a certain distance from the medical instrument (for example a distance less than or equal to 30 mm), the movement of the tool guide 14 is slowed down to make the practitioner feel the approach of the insertion pose and limit the risk of collision between the tool guide and the medical instrument. The practitioner can then open the clamp of the tool guide 14 and continue to move the tool guide closer to the medical instrument. The constrained manual behavior is sufficiently stable and intuitive so that a single hand of the practitioner is sufficient to move the tool guide while keeping the clamp open.If the alignment is not perfect, the practitioner can adjust the position of the medical instrument using his other hand (the one not manipulating the instrument guide).

[0117] Optionally, once a very small distance from the insertion position has been reached (for example, a distance less than or equal to 3 mm), the movement of the tool guide 14 ends automatically until the insertion position and the cooperative manual movement stops. The practitioner can then release the clamp so that the medical instrument 15 is again held by the tool guide 14. The practitioner can then proceed with the insertion of the medical instrument 15 up to the target point.

[0118] Throughout the procedure, the navigation system makes it possible to track the current position of the tool guide 14 and / or the patient reference 20. Information indicating whether the tool guide 14 is correctly positioned to follow the planned trajectory 41 may in particular be provided by a user interface. This indication may be visual (for example, information displayed on a screen of the medical robot or on an augmented reality headset connected to the medical robot), audible (for example, via a sound or a message spoken by a loudspeaker of the medical robot 10) or haptic (for example, via a vibration of the tool guide 14). The user interface may also indicate to the user which particular movement (free automatic movement, predictable automatic movement, or cooperative manual movement) is currently in progress or ready to be triggered by a user command (for example, by pressing the pedal 19).In particular, at the end of the predictable automatic movement, the user interface can indicate to the practitioner that it is up to him to move the tool guide 14 to grasp the partially inserted medical instrument 15.

Claims

Claims 1. Medical robot (10) for assisting a practitioner during a minimally invasive medical intervention on an anatomy of interest (45) of a patient (20), the medical robot (10) comprises a robotic arm (13) a distal end of which is equipped with a tool guide (14) intended to guide the insertion of at least part of a medical instrument (15) into the body of the patient (20) according to a planned trajectory (41), said tool guide (14) being coupled to a force sensor (16), the medical robot (10) comprises a control unit (12) configured to control the robotic arm (13) in order to move the tool guide (14), characterized in that the control unit (12) is configured to determine, from the planned trajectory (41), an insertion pose (103) and an offset pose (102) of the tool guide (14), the offset pose (102) lying in a plane (104) orthogonal to the planned trajectory (41) and passing through the insertion pose (103),and to carry out a sequence of movements of the robotic arm (13) successively comprising:, - an automatic movement to move the tool guide (14) to the offset position (102), - a cooperative manual movement for moving the tool guide (14) from the offset position (102) to the insertion position (103), the cooperative manual movement being controlled to constrain the movement of the tool guide (14) on the plane (104) orthogonal to the planned trajectory (41) and passing through the insertion position (103), such that the only possible movements of the tool guide (14) during the cooperative manual movement are in this plane (104), the speed of movement of the tool guide (14) during the cooperative manual movement being determined as a function of a force exerted by the practitioner on the tool guide (14), said force being measured by the force sensor (16).

2. Medical robot (10) according to claim 1 wherein the tool guide has a guide axis (XX') and a main axis (ZZ') orthogonal to the guide axis (XX'), the insertion pose (103) being such that, at the insertion pose, the guide axis (XX') coincides with the axis (TT') of the planned trajectory (41), and for which the only possible movements of the tool guide (14) during the cooperative manual movement are a translation along the main axis (ZZ') of the tool guide (14) and optionally a rotation around the axis (TT') of the planned trajectory (41).

3. Medical robot (10) according to any one of claims 1 to 2 wherein the control unit (12) is configured to determine an approach pose (101), and the automatic movement successively comprises: - a free automatic movement to move the tool guide (14) to the approach position (101), - a predictable automatic movement to move the tool guide (14) from the approach position (101) to the offset position (102).

4. The medical robot (10) of claim 3 wherein the predictable automatic motion comprises linear motion contained within a plane comprising the planned trajectory (41) and the approach pose (101).

5. Medical robot (10) according to claim 4 wherein the predictable automatic movement is a linear movement parallel to the planned trajectory (41).

6. Medical robot (10) according to any one of claims 3 to 5 wherein the predictable automatic movement comprises a linear movement contained in a plane orthogonal to the axis (TT') of the planned trajectory (41), and passing through the insertion pose (103).

7. Medical robot (10) according to any one of claims 1 to 6 wherein, during the cooperative manual movement, the speed of movement of the tool guide (14) is determined as a function of a gain factor applied to the force exerted by the practitioner, said gain factor also being calculated as a function of the force exerted by the practitioner.

8. Medical robot (10) according to claim 7 wherein the value of the gain factor is calculated as follows: where G(f) is the gain factor, K is a constant, |f| is the force exerted by the practitioner on the tool guide (14), Emin and E ma x correspond respectively to a minimum value and a maximum value for the effort exerted by the practitioner.

9. Medical robot (10) according to any one of claims 1 to 8 wherein the speed of movement of the tool guide (14) is determined as a function of a distance between a current pose of the tool guide (14) and the insertion pose (103).

10. Medical robot (10) according to any one of claims 1 to 9 wherein the control unit (12) is configured to prohibit any movement of the tool guide (14) for at least a predetermined duration when the insertion position (103) is reached.

11. Medical robot (10) according to any one of claims 1 to 10 wherein the robotic arm (13) is an articulated arm having at least six degrees of freedom.

12. Medical robot (10) according to any one of claims 1 to 11 wherein the insertion pose (103) and / or the planned trajectory (41) is determined from a control medical image on which the partially inserted medical instrument 15 is visible.

13. Medical robot (10) according to any one of claims 1 to 12 comprising a user interface configured to provide information indicating whether the tool guide (14) is correctly positioned to follow the planned trajectory (41).

14. A medical robot (10) according to any one of claims 1 to 13 comprising a user interface configured to provide information indicating which movement, among a set of predefined movements, is currently in progress or ready to be triggered by a user command, said set of predefined movements comprising free automatic movement, predictable automatic movement and cooperative manual movement.

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