IL318977A

IL318977A - Collaborative medical robot for securing the insertion of medical instruments

Info

Publication number: IL318977A
Application number: IL318977A
Authority: IL
Original assignee: Quantum Surgical
Priority date: 2023-03-16
Filing date: 2024-02-01
Publication date: 2025-04-01
Also published as: EP4554506A1; WO2024188531A1; FR3146587A1; KR20250158990A; JP2026508455A; CA3265656A1; CN120187376A

Description

WO 2024/188531 PCT/EP2024/052454 Collaborative medical robot for securing the insertion of medical instruments Field of the invention The present application pertains to the field of robotic devices for assisting a practitioner during a medical intervention. More particularly, the application relates to a medical robot comprising a robotic arm provided with a tool guide for holding, guiding and releasing a medical instrument during a minimally invasive medical intervention. Prior art Minimally invasive or percutaneous medical interventions may require a practitioner to insert one or more medical instruments (for example a needle, a probe, a catheter, etc.) into a patient’s body to a certain depth in order to reach a target point within an anatomy of interest (for example a tumor in the liver, lungs, kidneys or bones). When the procedure of inserting the medical instrument is performed entirely by the practitioner, the result of the intervention is very much dependent on the skill of the practitioner. The precision of the procedure can be improved with the assistance of remote-controlled medical robots. Here too, the success of the intervention is still partly dependent on the skill of the practitioner and may require continuous acquisition of medical images of the patient, which involves subjecting the patient to high doses of radiation. In order to further improve the precision of the insertion procedure and to limit the radiation doses on the patient, it is possible to use automatically controlled robotic arms. For example, the practitioner indicates, on a pre-interventional medical image, a trajectory that the medical instrument has to follow from an entry point located at the level of the patient’s skin until it reaches a target point within the anatomy of WO 2024/188531 - 2 - PCT/EP2024/052454 interest of the patient. The robotic arm can be equipped with a tool guide for guiding the medical instrument along an axis corresponding to that of the planned trajectory. The robotic arm can then be controlled to automatically adopt an insertion position (placement and orientation) in which the tool guide allows the medical instrument to be guided along the planned trajectory until it reaches the target point within the anatomy of interest. When the robotic arm is at the insertion position, the tool guide is usually located at a significant distance (several centimeters or more than ten centimeters or so) from the patient’s skin. This distance depends on the length of the medical instrument and on the depth to which the latter is to be inserted into the patient’s body (the insertion depth corresponds to the distance between the entry point at the level of the skin and the target point). It then happens that the medical instrument deviates from the planned trajectory when it pierces the patient’s skin at the entry point. This is because the medical instrument generally has a certain flexibility, and the greater the distance between the tool guide and the entry point at the moment of insertion, the greater the risk of deviation of the medical instrument from the planned trajectory. This problem of deviation (curvature) of a medical instrument is known, and one of the solutions most often used to address this problem is to calculate a deviation from the planned trajectory (see for example paragraphs [0188] to [0190] of the patent application US 2022/0265355 A1). For example, mathematical models can be used to determine the potential bending or twisting of a medical instrument (depending on its length, its diameter, the material used, etc.). This solution is not ideal due to precision errors in the estimation of the deviation. Another solution is to check, after insertion, whether the instrument has deviated from the trajectory WO 2024/188531 - 3 - PCT/EP2024/052454 and, if necessary, to correct the positioning of the instrument accordingly. This solution is also not ideal since it may require acquisition of additional medical images (greater irradiation of the patient) and insertion of the medical instrument into the patient several times (prolonging the duration of the intervention). In addition, in the case of percutaneous ablation of a tumor, this solution may also lead to an increased risk of spread of the tumor. The international patent application WO 2022/ 195210 A1 describes a medical robot with a robotic arm provided with a tool guide. The medical robot is configured to control the movement of the robotic arm in a collaborative mode in which the speed of movement of the tool guide is determined as a function of a force exerted by the practitioner on the tool guide. The movement of the tool guide can also be constrained in particular directions. However, said document does not address the problem of deviation of the medical instrument during its insertion into the patient’s body. Patent application US 2016/242849 A9 describes a medical robot comprising a robotic arm provided with an effector coupled to a distal end of the arm. The effector can comprise a surgical instrument. Patent application US 2019/282301 A1 describes an image-based guidance system making it possible to define the trajectory of a needle by setting the locations of an insertion point and a target point. Disclosure of the invention The object of the present application is to remedy all or some of the drawbacks of the prior art, in particular those set out above, by proposing a solution for more reliably securing the angle and depth of insertion of a medical instrument during a minimally invasive intervention. To this end, and according to a first aspect, a medical robot is proposed for assisting a practitioner WO 2024/188531 - 4 - PCT/EP2024/052454 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 provided with a tool guide intended to guide the insertion of at least part of a medical instrument into the patient’s body along a planned rectilinear trajectory between an entry point located at the level of the skin of the patient and a target point located within the anatomy of interest. 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 and memorize an insertion position from the planned trajectory. In an "automatic control" mode, the control unit is configured to move the tool guide autonomously to the insertion position. In a "collaborative axial control" mode, the control unit is configured to determine, with the aid of a force sensor coupled to the tool guide, a force exerted by the practitioner on the tool guide, and to move the tool guide as a function of the force thus determined. In the collaborative axial control mode, the movement of the tool guide is constrained in order to authorize only: - a movement allowing a translation of the tool guide along the axis of the planned trajectory, or - a movement allowing a translation of the tool guide along the axis of the planned trajectory and a rotation of the tool guide about the axis of the planned trajectory. In the collaborative axial control mode, the control unit is configured to provide haptic feedback to the practitioner when the tool guide returns to the insertion position. In the present application, the term "position" is to be understood as meaning "placement and orientation". The "insertion position" corresponds to a position of the tool guide in which the tool guide has a guide duct for guiding the medical instrument along the WO 2024/188531 - 5 - PCT/EP2024/052454 axis of the planned trajectory and to the exact depth for reaching the target point. During the insertion, the medical instrument is guided in translation by the guide duct until it reaches a stop position (part of the medical instrument then comes into abutment 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 part of the instrument that has penetrated the patient’s body is located at the target point. When the part of the medical instrument intended to penetrate the patient’s body has axial symmetry along the axis of the guide duct, the different positions of the tool guide that are obtained by rotation along this axis correspond to the same insertion position. The collaborative axial control mode allows the tool guide to be moved from the insertion position to a position as close as possible to the patient’s skin, at the entry point, while maintaining the axis of the planned trajectory. The medical instrument can then be placed in the tool guide and partially inserted into the patient’s body when the tool guide is as close as possible to the patient’s skin, in order to avoid bending of the medical instrument and deviation from the planned trajectory. The collaborative axial control mode and the haptic feedback then allow the tool guide to be relocated exactly to the insertion position (the medical instrument is then still partially inserted). Once the tool guide is relocated to the insertion position, the insertion of the medical instrument can be completed as far as the stop position in order to reach the target point. When the tool guide is relocated to the insertion position in the collaborative axial control mode, the medical instrument is in place and the robotic arm or the practitioner may potentially obstruct the line of sight of an optical navigation system used to determine the position of the tool guide. The fact that the insertion position has previously been recorded in the frame of WO 2024/188531 - 6 - PCT/EP2024/052454 reference of the medical robot allows the latter to be able to autonomously relocate the tool guide to the insertion position without using an optical navigation system. The haptic feedback allows the practitioner to feel the exact moment when the insertion position is reached. The haptic feedback can optionally also allow the practitioner to sense the approach of the insertion position. This enables an easy and intuitive return to the insertion position. The haptic feedback gives the user the impression of a virtual notch when the tool guide reaches the insertion position. In particular embodiments, the invention can further comprise one or more of the following features, taken alone or in any technically possible combinations. In particular embodiments, in the collaborative axial control mode, when the distance between a current position of the tool guide and the insertion position is less than a first threshold, the control unit is configured to calculate a speed of movement of the tool guide as a function of a gain factor applied to the force exerted by the practitioner on the tool guide, the value of the gain factor decreasing progressively as a function of the distance between the current position and the insertion position. The decrease in the speed of movement of the tool guide allows the practitioner to sense the approach of the insertion position. In particular embodiments, in the collaborative axial control mode, when the distance between a current position of the tool guide and the insertion position is less than a second threshold, the control unit is configured to limit or maintain the speed of movement of the tool guide at a predetermined speed regardless of the force exerted by the practitioner on the tool guide. In particular embodiments, in the collaborative axial control mode, the control unit is configured to prohibit any movement of the tool guide for a WO 2024/188531 - 7 - PCT/EP2024/052454 predetermined duration when the insertion position is reached. The abrupt stop in the movement of the tool guide allows the practitioner to feel the exact moment when the insertion position is reached. The insertion position can in particular be determined with the aid of a navigation system (for example an optical navigation system) and a pre-interventional medical image. Thus, in particular embodiments, the tool guide comprises at least one marker detectable by a navigation system, and the control unit is configured to: - receive, from said navigation system, a first item of information relating to a position of the tool guide in a reference frame of the navigation system, - receive, from said navigation system, a second item of information relating to an insertion position, in the reference frame of the navigation system, that the tool guide has to adopt in order to guide the medical instrument along the planned trajectory until the target point is reached, - determine the insertion position, in a reference frame of the medical robot, from the first item of information and the second item of information. In particular embodiments, the second item of information corresponds to a position, in the reference frame of the navigation system, of a patient reference intended to be placed on the patient in proximity to the anatomy of interest. The patient reference comprises at least one marker detectable by the navigation system and at least one radiopaque marker. The control unit is configured to determine the insertion position from the position of the patient reference and from the planned trajectory. The planned trajectory is defined relative to the position of the patient reference with the aid of WO 2024/188531 - 8 - PCT/EP2024/052454 a pre-interventional medical image on which can be seen the anatomy of interest of the patient and said at least one radiopaque marker of the patient reference. In particular embodiments, the part of the medical instrument intended to penetrate the patient’s body has axial symmetry along an axis which, during the insertion of the medical instrument, corresponds to the axis of the planned trajectory. In the collaborative axial control mode, the movement of the tool guide is constrained in order to limit it to a movement allowing a translation of the tool guide along the axis of the planned trajectory and a rotation of the tool guide about the axis of the planned trajectory. With such arrangements, the part of the instrument intended to penetrate the patient’s body is unchanged when it is rotated about the axis of symmetry. In this case, the collaborative axial control mode can act both in translation and in rotation about the axis of the trajectory. This makes it possible to modify the position of the tool guide without modifying the axis of the trajectory (the axis of the trajectory is coincident with the axis of the guide duct, and the guide duct remains identical during rotation of the tool guide about this axis). When the tool guide is brought close to the patient’s skin, the rotational control mode allows the position of the tool guide to be modified while keeping the guide duct along the axis of the trajectory. This makes it possible, for example, to avoid collision of the tool guide with an obstacle (for example the patient or a marker positioned on the patient’s body). At the insertion position, the rotational control allows the position of the tool guide to be modified without changing the insertion position (any rotation of the tool guide about the axis of the trajectory corresponds to the same insertion position because the guide duct remains identical). This can in particular help free the working space available to the practitioner.

WO 2024/188531 - 9 - PCT/EP2024/052454 In particular embodiments, the tool guide comprises two jaws. Each jaw comprises a groove. The jaws can be driven between a closed position, in which the grooves are contiguous and define a guide duct for holding the medical instrument and guiding it in translation, and an open position, in which the grooves are spaced apart from each other for placement or release of the medical instrument. The guide duct adopts, at the insertion position, a position coaxial to the planned trajectory. The change from the closed position to the open position can be brought about by the practitioner pressing on a lever formed by a support surface of one of the jaws. In the collaborative axial control mode, the control unit is configured to transpose the force exerted by the practitioner on the tool guide to a virtual application point positioned such that the axis of a pressure force exerted on the lever and the axis passing through a real application point of the pressure force and the virtual application point form an angle of less than twenty degrees. When the tool guide is as close as possible to the patient’s skin, the practitioner presses on the lever to open the jaws in order to put the medical instrument in place. The practitioner then releases the lever, such that the tool guide holds the medical instrument, and proceeds to partially insert the medical instrument. Before bringing the tool guide to the insertion position in order to complete the insertion of the medical instrument, the practitioner again presses on the lever in order to open the jaws of the tool guide. The particular position of the force application point in the control law makes it possible to avoid an untimely rotation of the tool guide when the practitioner presses on the lever to open the jaws of the tool guide before relocating it to the insertion position. This allows intuitive transition from translational control to rotational control: pressing on the lever does not cause rotation of the tool guide; by contrast, pressure WO 2024/188531 - 10 - PCT/EP2024/052454 exerted on another part of the tool guide can cause rotation of the tool guide. In particular embodiments, the robotic arm has at least six degrees of freedom. The use of at least six degrees of freedom advantageously makes it possible to achieve any position of the tool guide in three-dimensional space. Presentation of the figures The invention will be better understood on reading the following description, given as a non-limiting example and with reference to the following figures: [Fig. 1] shows a schematic representation of an embodiment of a medical robot according to the invention, [Fig. 2] shows a schematic representation of a trajectory that a medical instrument is to follow from an entry point at the level of the patient’s skin to a target point in or near a region to be treated within the anatomy of interest of the patient, [Fig. 3] shows a schematic representation of the robotic arm of the medical robot illustrated in Figure 1, [Fig. 4] shows a schematic representation of the tool guide attached to a distal end of the robotic arm illustrated in Figure 3, [Fig. 5] shows a detailed representation of the tool guide illustrated in Figure 3, [Fig. 6] shows another representation of the tool guide, when the medical instrument is held by the tool guide, [Fig. 7] shows a schematic representation of an embodiment of a patient reference, [Fig. 8] shows an illustration of the collaborative axial control mode, the tool guide being located at the insertion position, [Fig. 9] shows an illustration of the collaborative axial control mode, the tool guide having been moved in translation from the insertion position, along the axis of the planned trajectory, to approach the entry point, WO 2024/188531 - 11 - PCT/EP2024/052454 so as to allow partial insertion of the medical instrument, [Fig. 10] shows an illustration of the collaborative axial control mode, the tool guide having been relocated to the insertion position in order to complete the insertion of the medical instrument until it reaches the target point, [Fig. 11] shows a schematic representation of an embodiment of the tool guide’s holding system, [Fig. 12] shows a schematic representation of a force applied to one of the jaws of the holding system of Figure in order to move it to the open position, [Fig. 13] shows a schematic representation of a force applied to one of the jaws of the holding system of Figure in order to hold it in the open position, [Fig. 14] shows a representation, for a particular example of implementation, of the variation in the speed of movement of the tool guide as a function of the distance separating the current position of the tool guide and the insertion position, for a constant force exerted by the practitioner on the tool guide. In these figures, identical references from one figure to another designate identical or similar elements. For the sake of clarity, the elements shown are not necessarily to the same scale, unless otherwise indicated. Detailed description of an embodiment of the invention Figure 1 shows a schematic representation of an example of an embodiment of a medical robot 10 according to the invention. The medical robot 10 is used to assist a practitioner during a minimally invasive medical intervention on an anatomy of interest of a patient positioned on an intervention table 21. This type of intervention generally requires the practitioner to insert one or more medical instruments into the body of the patient 20 from an entry point located at the level of the patient’s skin to a certain WO 2024/188531 - 12 - PCT/EP2024/052454 depth in order to reach a target point in or near a region of the anatomy of interest to be treated. The aim of the intervention may in particular be to perform 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 specific anatomical region. The anatomy of interest may correspond to an organ or a bone, for example the liver, a lung, a kidney, the brain, a vertebra, the tibia, the femur, the hip, the knee, the pelvic bones, the pelvis, etc. The medical instrument 15 may be a needle, an electrode, a probe, a drill, a trocar, a screw, etc. Figure 2 illustrates a rectilinear trajectory that the medical instrument 15 has to follow from an entry point 43 located at the level of the skin of the patient 20 to a target point 44 that is to be reached in or near a region to be treated within the anatomy of interest 45 of the patient 20. 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 allow 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. Attached to the other end of the robotic arm 13 is a tool guide 14 intended to guide a medical instrument 15 (for example a needle, a probe, an electrode, or a trocar). The medical robot 10 is used to assist a practitioner in positioning, maintaining the position of or guiding the medical instrument 15 during the medical intervention. The medical robot 10 then serves as a third hand for the practitioner. As is 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). The control unit 12 comprises at least one WO 2024/188531 - 13 - PCT/EP2024/052454 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 in order to implement the different steps of a method for positioning the robotic arm 13 and more particularly the tool guide 14. The robotic arm 13 is also illustrated in Figure 3. In the example considered and illustrated in Figures and 3, the robotic arm 13 comprises six rotoid articulations 131 to 136 conferring six degrees of freedom, making it possible to place and/or move the medical instrument 15 in any position of the three-dimensional space. Advantageously, the articulations 1to 135 of the robotic arm 13 are not aligned and have an offset relative to each other, which allows a greater number of possible configurations of the robotic arm 13. Each articulation comprises at least one encoder making it possible to know its angular position in real time. A configuration of the robotic arm 13 then corresponds to a set of parameter values taken by the articulations 1to 136 (for example the value of an angle of rotation for each articulation). The rotoid articulation 1corresponds to a rotation about a main axis of the tool guide 14. It should be noted that, when the medical instrument 15 has axial symmetry for the part of the instrument that is intended to penetrate the patient’s body, it is not essential to be able to effect rotation about the axis of symmetry (five degrees of freedom are in fact sufficient to guide and release the medical instrument in this case). This additional degree of freedom makes it possible to be in a situation of redundancy and to have an infinite number of possible configurations of the robotic arm 13 for a given position of the tool guide 14. This situation of redundancy is particularly useful for adapting to constraints related WO 2024/188531 - 14 - PCT/EP2024/052454 to the positioning of the patient 20 or to the configuration of the operating room. As is illustrated in Figures 3 and 4, the tool guide 14 is attached to the robotic arm 13 by means of a flange 17. The tool guide has a main axis 145 represented in Figure 4 by a dotted line. 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 manually moving the robotic arm 13. As is illustrated in Figures 5 and 6, the tool guide 14 comprises a body 141 with a base 142 intended to be attached to the flange 17 using screws 143, and also a holding system 50 comprising two parts movable relative to each other. The holding system 50 is intended to hold the medical instrument 15 at that 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 driven by a drive system such as a gear, a cam, a screw with reverse threads and/or a linear actuator, in order to block or release the medical instrument 15. The tool guide makes it possible, for example, to guide medical instruments of different diameters. For example, such a guide makes it possible to guide medical instruments whose diameter is between 11 and 21 gauges. Gauge is a unit of measurement commonly used to define the external diameter of a medical instrument such as a needle, probe or catheter (11 gauges correspond to an external diameter of 2.946 mm; 21 gauges correspond to an external diameter of 0.812 mm). As is illustrated in Figure 1, a navigation system 30 can be used to provide the control unit 12 of the medical robot 10 with information relating to a current position of the tool guide 14 and to an insertion position that the tool guide has to reach. The current position and the insertion position are, for example, initially defined in a reference frame of the navigation system 30 and then transformed into positions in a WO 2024/188531 - 15 - PCT/EP2024/052454 reference frame of the medical robot 10 by the control unit 12. The control unit 12 can then be configured (in what is called an "automatic control" mode, without intervention by the practitioner) to automatically move the robotic arm 13 such that the latter reaches the insertion position. The navigation system 30 and the control unit 12 of the medical robot 10 can exchange data via communication means (wired or wireless). The insertion position corresponds to a position of the tool guide 14 in which the latter is able to guide the medical instrument 15 along the axis of the planned trajectory 41 and to the exact depth in order to reach the target point 44 within the anatomy of interest 45. The holding system 50 of the tool guide 14 forms, for example, a guide duct in which at least part of the medical instrument 15 is intended to slide during the insertion of the medical instrument 15 into the body of the patient 20. At the insertion position, the axis of the trajectory 41 is then coincident with the axis of the guide duct. The insertion position is defined as a function of the length of the medical instrument 15 and as a function of the insertion depth corresponding to the planned trajectory 41. During the insertion, the medical instrument is guided in translation by the guide duct until it reaches a stop position (a part of the medical instrument then comes into abutment against the tool guide and prevents any further insertion). The insertion position is defined such that when this stop position is reached, the distal end of the part of the instrument that has penetrated the patient’s body is located at the target point. When the part of the medical instrument intended to penetrate the patient’s body has axial symmetry along the guide duct (i.e. along the planned trajectory), the different positions of the tool guide that are obtained by rotation along this axis correspond to the same insertion position (in other words, the insertion WO 2024/188531 - 16 - PCT/EP2024/052454 position corresponds to the position adopted by the guide duct, formed by the holding system 50 of the tool guide 14, when the tool guide 14 is in position for inserting the medical instrument 15). In the example considered, the navigation system 30 is an optical navigation system. The navigation system comprises at least two optical sensors corresponding, for example, to two sensors of a stereoscopic camera operating in the infrared radiation range or in the visible light range. As is illustrated in Figures 5 and 6, the tool guide 14 comprises stubs 144 intended to receive optical markers 147. Advantageously, the tool guide 14 comprises at least three optical markers 147 so that the position of the tool guide 14 can be determined in the three spatial dimensions of the reference frame of the navigation system 30. The respective positions of the optical markers 147 of the tool guide relative to one another are known a priori by the navigation system and/or by the control unit 12. Advantageously, the geometric shape of each optical marker 147 can also be known a priori. In the example illustrated in Figure 6, the optical markers 147 are spherical in shape. In the illustration in Figure 6, the tool guide 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). The optical markers 147 may be passive or active. Passive optical markers reflect optical radiation emitted by another element, for example the navigation system 30. Passive optical markers may correspond, for example, to reflective spheres detectable by an infrared stereoscopic camera (this is what is used, for example, in the Polaris® navigation systems manufactured by Northern Digital Inc.), or to black and white patterns visible by a stereoscopic camera (this is what is used, for example, WO 2024/188531 - 17 - PCT/EP2024/052454 in the MicronTracker® navigation system from the company ClaroNav). Active optical markers themselves emit optical radiation, for example infrared radiation, detectable by the navigation system 30. As is illustrated in Figure 1, all of the markers 147 present on the tool guide 14 correspond to a robot reference 18. The use of at least three optical markers 1makes it possible to define a plane and therefore a direct orthonormal three-dimensional reference frame with a z axis normal to the plane and x and y axes in the plane, so that the reference frame is direct. This thus makes it possible to determine the position of the reference frame formed from the optical markers 147 which represent 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 x, y or z axes and a rotation about each of these axes. It should however be noted that a single optical marker having a characteristic geometric shape in three dimensions could be used instead of the set of spherical optical markers 147. As is illustrated in Figure 1, a patient reference 22 is placed on the patient 20 in proximity to the anatomy of interest. Figure 7 shows a schematic representation of the patient reference 22. The patient reference 22 comprises at least three optical markers 221, such that the position of the patient reference can be determined in the three spatial dimensions of the reference frame of the navigation system 30. The respective positions of the optical markers 221 of the patient reference 22 relative to one another are known a priori by the navigation system 30 and/or by the control unit 12. Advantageously, the geometric shape of each optical marker 221 can also be known a priori. In the example illustrated in Figure 7, the patient reference comprises three optical markers 221 of spherical shape. The spherical shape makes it possible to optimize WO 2024/188531 - 18 - PCT/EP2024/052454 the reflection of the optical radiation. What has been mentioned above for the active or passive type of optical markers 147 of the tool guide 14 is also true for the optical markers 221 of the patient reference 22. Here again, it would be conceivable to use a single optical marker having a characteristic geometric shape in three dimensions instead of the three spherical optical markers 221. In the remainder of the description, it is considered by way of non-limiting example that the optical sensors 31 of the navigation system 30 and the various optical markers 147, 221 are designed to operate with infrared optical radiation. It is further considered that the optical markers 147, 221 are passive markers. The optical sensors 31 of the navigation system 30 are configured to emit infrared radiation. This infrared radiation is reflected by the various optical markers 147, 221 toward the optical sensors 31. The optical sensors 31 are configured to receive this reflected infrared radiation. The navigation system 30 can then determine the distance between an optical marker 147, 2and an optical sensor 31 by measuring the time taken by an infrared ray to make a round trip between said optical sensor 31 and said optical marker 147, 221. By knowing the distance between each optical marker 147, 221 and each optical sensor 31, and by knowing a priori the arrangement of the optical markers 147, 221 relative to one another on the tool guide 14 and on the patient reference 22, it is possible to determine the position of the tool guide 14 and of the patient reference 22 in the reference frame of the navigation system 30. The insertion position that the tool guide 14 has to reach can in particular be defined from the position of the patient reference 22. For this purpose, and as is illustrated in Figure 7, the patient reference 22 also comprises radiopaque markers 222 which are visible on a medical image acquired by a medical imaging device (for example by computed tomography, magnetic resonance, WO 2024/188531 - 19 - PCT/EP2024/052454 ultrasound, tomography, positron emission, etc.). The respective positions of the radiopaque markers 2relative to one another are known a priori by the navigation system 30 and/or by the control unit 12. Advantageously, the geometric shape of the radiopaque markers 222 may also be known a priori. Preferably, the patient reference 22 comprises at least three radiopaque markers 222. The radiopaque markers 222 may be ceramic beads, for example. It should be noted, however, that a single radiopaque marker having a characteristic geometric shape in three dimensions could be used instead of the three spherical radiopaque markers 222. It is thus possible to plan the medical intervention from a pre-interventional medical image acquired on the patient provided with the patient reference 22 (this may in particular be a three-dimensional image). 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 has to adopt in order to guide the medical instrument 15 to perform the medical intervention. The insertion position can then be stored by the control unit 12. The planning includes determining, on the pre- interventional image 40, the trajectory 41 to be followed by the medical instrument 15 (e.g. a needle) between an entry point 43 located at the level of the skin of the patient 20 and a target point 44 located in or near a region to be treated (e.g. a tumor) within the anatomy of interest 45 (e.g. the liver) of the patient 20. The patient reference 22 (more precisely the radiopaque elements 222 of the patient reference 22) is visible on the pre-interventional image 40. The position of the patient reference 22 can therefore be defined in the medical image. The insertion position of the tool guide for following the trajectory 41 can then be defined relative to the position of the patient reference 22.

WO 2024/188531 - 20 - PCT/EP2024/052454 The entry point 43, the target point 44 and the patient reference 22 can be determined on the image automatically (e.g. using an automatic segmentation algorithm), semi-automatically (with the help of the practitioner), or manually by the practitioner. It should be noted that the determination of the trajectory can also be carried out on a pre-operative image acquired several days before the intervention (image acquired without the patient being provided with the patient reference). The pre-operative image can then be registered with the pre-interventional image 40 on which the patient reference 22 is visible, in order to obtain a relative position of the patient reference with respect to the trajectory, and therefore with respect to the insertion position of the tool guide 14. In the example considered, the navigation system is configured to provide the control unit 12 of the medical robot 10 with the current position of the tool guide 14 (or more precisely the position of the robot reference 18) in the reference frame of the navigation system 30. However, the control unit 12 of the medical robot 10 knows the current position of the tool guide in the reference frame of the medical robot 10 (via the encoders of the articulations 131 to 136). The control unit 12 can therefore determine the transformation to be carried out in order to define a position in the reference frame of the medical robot 10 from a position in the reference frame of the navigation system 30. The navigation system 30 is also configured to provide the control unit 12 of the medical robot with the position of the patient reference 22 in the reference frame of the navigation system 30. The control unit can then define the position of the patient reference in the reference frame of the medical robot 10. Now, by virtue of the pre-interventional image 40, the control unit 12 of the medical robot 10 knows the insertion position that the tool guide 14 has to reach relative to the position of the patient reference 22. The control WO 2024/188531 - 21 - PCT/EP2024/052454 unit 12 can therefore determine the insertion position, in the reference frame of the medical robot, that the tool guide 14 has to reach from the information provided by the navigation system 30. The control unit 12 can then be configured to automatically move (in what is called the "automatic control" mode) the robotic arm 13 such that the latter reaches the insertion position. The movements of the robotic arm 13 are, for example, conditioned by the selection of a control mode on a user interface of the medical robot 10 and by the activation of the selected mode by a control pedal 19. The automatic control mode corresponds to a mode in which the robotic arm 13 is completely controlled by the control unit 12. The robotic arm 13 is then moved automatically, without intervention of the practitioner. In what is called a "collaborative control" mode, the control unit 12 is configured to determine, using the force sensor 16, a force exerted by the practitioner on the tool guide 14, and to move the tool guide 14 according to the force thus determined. This corresponds to a mode in which the practitioner can manually move the robotic arm 13 himself, but with control of the movement of the robotic arm 13 by the control unit 12 (for example in order to limit the speed and/or the possible directions of movement of the robotic arm 13). There may be several "collaborative control" modes. For example, a "collaborative approach control" mode corresponds to a mode in which the practitioner moves the robotic arm 13 in order to cause the tool guide to approach the patient, so that the robotic arm 13 enters the field of view of the optical navigation system 30. In this mode, it is of interest to control the speed of movement of the robotic arm 13 as a function of the force exerted by the practitioner on the robotic arm 13. In this mode, the movement of the robotic arm 13 is generally permitted in all directions. The robotic arm can then be moved automatically (in the automatic control mode) to the insertion position.

WO 2024/188531 - 22 - PCT/EP2024/052454 A "collaborative axial control" mode corresponds to a mode in which the practitioner can manually move the robotic arm 13, but only in such a way that the position of the tool guide 14 preserves the planned trajectory when the medical instrument 15 slides in the tool guide 14, that is to say in such a way that the axis of the guide duct formed by the holding system 50 of the tool guide 14 remains coincident with the axis of the planned trajectory 41. In other words, in the collaborative axial control mode, the control unit 13 is configured to prohibit any movement which would result in a modification of the position of the tool guide 14 such that the trajectory 41 would no longer be respected when the medical instrument 15 slides in the tool guide 14. In a particular embodiment, the movement of the tool guide 14 in collaborative axial control is constrained to authorize only a movement allowing a translation of the tool guide 14 along the axis of the planned trajectory 41. In the collaborative axial control mode, the control unit 12 is configured to provide haptic feedback to the practitioner when the tool guide 14 returns to the insertion position. Such arrangements allow for an easy and intuitive return to the insertion position. Figures 8 to 10 illustrate the collaborative axial control mode with a translation of the tool guide close to the body of the patient 20 in order to partially insert the medical instrument 15 therein before returning the tool guide 14 to the insertion position. In Figure 8, the tool guide is located at the insertion position. In Figure 9, the tool guide 14 has been moved in translation along the axis of the planned trajectory in order to be brought closer to the patient’s body, as close as possible to the patient’s skin 20, at the entry point 43. As is illustrated in Figure 9, the medical instrument 15 can then be placed in the tool guide 14 and partially inserted into the body of the patient 20 when WO 2024/188531 - 23 - PCT/EP2024/052454 the tool guide 14 is as close as possible to the patient’s skin, in order to avoid bending of the medical instrument and deviation from the planned trajectory 41. The collaborative axial control mode and the haptic feedback then make it possible to relocate the tool guide 14 exactly to the insertion position (the medical instrument is then still partially inserted). Figure 10 illustrates the situation where the tool guide 14 is relocated to the insertion position. Once the tool guide 14 is relocated to the insertion position, the insertion of the medical instrument 15 can be finalized to reach the target point 44. It can happen that the line of sight between the navigation system 30 and a reference (patient reference or robot reference 18) is obstructed, which may prevent information being obtained relating to the position of the reference. In particular, when the tool guide 14 is relocated to the insertion position in the collaborative axial control mode, the medical instrument is in place and could potentially obstruct the line of sight between the navigation system 30 and robot reference 18. The fact that the insertion position (in the reference frame of the medical robot) has been recorded makes it possible to relocate the tool guide to the insertion position without having to use a navigation system 30. In another particular embodiment, the movement of the tool guide 14 in collaborative axial control is constrained in order to authorize not only a movement allowing translation of the tool guide 14 along the axis of the planned trajectory 41, but also a movement allowing rotation of the tool guide 14 about the axis of the planned trajectory 41 (any other movement of the tool guide 14 being prohibited). Indeed, when the part of the medical instrument 15 intended to penetrate the body of the patient 20 has axial symmetry along the axis of the trajectory 41, it is advantageous for the collaborative axial control mode to be able to act both in translation WO 2024/188531 - 24 - PCT/EP2024/052454 and in rotation about the axis of the trajectory 41. Thus, when the tool guide 14 is brought close to the skin of the patient 20, the rotation control makes it possible to modify the position of the tool guide 14 while keeping the guide duct along the axis of the trajectory 41 (the axis of the trajectory is coincident with the axis of the guide duct, and the guide duct remains identical during a rotation of the tool guide 14 about this axis). This makes it possible, for example, to avoid a collision of the tool guide 14 with an obstacle (for example with the patient reference 22 or with the actual patient 20). At the insertion position, the rotation control mode makes it possible to modify the position of the tool guide without modifying the insertion position (any rotation of the tool guide 14 about the axis of the trajectory 41 corresponds to the same insertion position because the guide duct remains identical). This can in particular make it possible to free the working space available to the practitioner. The haptic feedback allows the practitioner to feel the exact moment when the insertion position is reached. The haptic feedback can optionally also allow the practitioner to sense the approach of the insertion position. This allows for an easy and intuitive return to the insertion position. For example, in particular embodiments, the control unit 12 can be configured to decrease the speed of movement of the tool guide 14 when the tool guide approaches the insertion position. Such arrangements allow the practitioner to sense the approach of the insertion position. The speed of movement of the tool guide 14 can in particular be controlled as a function of a distance between a current position of the tool guide and the insertion position. For example, the speed of movement of the tool guide 14 is controlled as a function of a gain factor applied to the force exerted by the practitioner on the tool guide 14, and the control unit WO 2024/188531 - 25 - PCT/EP2024/052454 is configured to progressively reduce the value of the gain factor as a function of the distance separating the current position and the insertion position. This progressive reduction of the gain factor may possibly be implemented only from the moment when the distance between the current position and the insertion position is less than a first threshold. Alternatively and/or in addition, when the distance between the current position of the tool guide and the insertion position is less than a second threshold, the control unit 12 can be configured to limit or maintain the speed of movement of the tool guide at a predetermined speed regardless of the force exerted by the practitioner on the tool guide 14. Such arrangements give the user the impression of a virtual notch when the tool guide 14 reaches the insertion position. The decrease in the speed of movement of the tool guide to a particularly low speed corresponds to a haptic feedback that allows the practitioner to sense the approach of the insertion position. Alternatively and/or in addition, the control unit 12 can also be configured to prohibit any movement of the tool guide 14 for a predetermined duration when the insertion position is reached. The abrupt stop of the movement of the tool guide corresponds to haptic feedback allowing the practitioner to sense the exact moment when the insertion position is reached. Figure 14 shows, for a particular example of implementation, the variation of the speed v of movement of the tool guide 14 as a function of the distance d separating the current position and the insertion position, for a constant force exerted by the practitioner on the tool guide 14. In the zones 61 and 62, the speed of movement of the tool guide 14 is determined by applying the gain factor to the force exerted by the practitioner. When the distance separating the current position and the insertion position is WO 2024/188531 - 26 - PCT/EP2024/052454 greater than a first threshold d1, the gain factor is constant (zone 61 in the figure). When the distance is between the first threshold d1 and a second threshold dless than d1, the gain factor gradually decreases with the distance (zone 62 in the figure). When the distance is less than the second threshold d2, the speed of movement of the tool guide 14 is forced to a predetermined value (zone 63 in the figure). When the distance becomes zero, the speed of movement of the tool guide 14 becomes zero for a predetermined duration. Other options could be considered for the haptic feedback (as alternatives and/or in addition to the options proposed above), for example a vibration of the tool guide 14 when the insertion position is reached. The control unit 12 can also be configured to provide a visual indication of the distance between a current position of the tool guide 14 and the insertion position, or of the arrival of the tool guide 14 at the insertion position. For example, the distance between the current position of the tool guide 14 and the insertion position can be displayed on a user interface (for example on a monitor-type display screen, or on a screen of an augmented reality mask) in the form of a number or a gauge. A symbol (for example a green circle) can further be displayed when the insertion position is reached, i.e. when the distance between the current position of the tool guide 14 and the insertion position becomes zero. The control unit 12 can also be configured to provide an acoustic indication of the distance between the current position of the tool guide 14 and the insertion position, or of the arrival of the tool guide at the insertion position. For example, an acoustic signal can be repeated with a frequency that increases as the distance between the current position of the tool guide 14 and the insertion position decreases. The acoustic signal can, for example, become a continuous sound when the insertion position is reached. Or a WO 2024/188531 - 27 - PCT/EP2024/052454 specific sound can be emitted when the insertion position is reached. Thus, the control unit 12 can be configured to provide information on the distance between a current position of the tool guide 14 and the insertion position, or on the arrival of the tool guide 14 at the insertion position, or even when the tool guide 14 exceeds the insertion position, using one or more indications from among a haptic indication, a visual indication and an acoustic indication. Figures 11 to 13 illustrate an exemplary embodiment of the holding system 50 of the tool guide 14. This embodiment of the holding system is similar to the one described in the patent application WO 2020/2012A1, with reference to Figures 7 to 8 of this application. In this exemplary embodiment, the holding system 50 of the tool guide 14 comprises two jaws 51, 55. The jaws and 55 can be driven between a closed position (as is illustrated in Figure 12) and an open position (as is illustrated in Figure 13). Each jaw has a groove 52, 56. The grooves 52, 56 extend transversely relative to teeth 53, 57 arranged so as to mesh with each other 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 contiguous and define a guide duct 59 for holding the medical instrument 15 and guiding it in translation. In the open position, the grooves 52 and 56 are spaced apart from each other for placement or release of the medical instrument 15. The closed position therefore corresponds to a position for guiding the medical instrument, while the open position corresponds to a position for releasing the medical instrument. At the insertion position, the guide duct adopts a position coaxial to the planned trajectory 41. The change from the closed position to the open position can be caused by a pressure force exerted by the practitioner on a lever 58 formed by a support surface WO 2024/188531 - 28 - PCT/EP2024/052454 of one of the jaws (the jaw 55 in the example illustrated in Figures 11 to 13). As is illustrated in Figures 12 and 13, in the collaborative axial control mode, the control unit 12 is configured to transpose the force exerted by the practitioner on the tool guide 14 to a virtual application point A’ positioned such that the axis of a pressure force ? ⃗ exerted on the lever 58 and the axis (AA’) passing through a real application point A of the pressure force ? ⃗ and the virtual application point A’ form a particularly small angle θ, for example less than twenty degrees, or even less than ten degrees. When the tool guide is very close to the patient’s skin, the practitioner presses the lever 58 to open the jaws 51, 55 in order to put the medical instrument 15 in place. The practitioner then releases the lever 58 so that the tool guide holds the medical instrument 15 (while allowing it to slide along the guide duct 59). The practitioner can then proceed with the partial insertion of the medical instrument 15. Before returning the tool guide 14 to the insertion position in order to finalize the insertion of the medical instrument 15, the practitioner can again press on the lever 58 in order to open the jaws 51, 55 of the tool guide. Alternatively, the practitioner does not press on the lever 58, and the jaws of the tool guide are closed during the sliding movements of the guide along the needle. The particular position of the virtual application point A’ of the forces taken into account in the control law makes it possible to avoid untimely rotation of the tool guide 14 when the practitioner presses on the lever 58 in order to open the jaws 51, of the tool guide 14 before relocating it to the insertion position. Indeed, as the angle θ is small, the torque of the pressure force ? ⃗ exerted on the lever 58 is small, and this makes it possible to avoid (or at least very greatly limit) the untimely rotation of the tool guide WO 2024/188531 - 29 - PCT/EP2024/052454 when the practitioner presses on the lever in order to open the jaws 51, 55 of the tool guide. This configuration allows an intuitive transition from a translational control mode to a rotational control mode: pressure on the lever 58 does not cause rotation of the tool guide 14; by contrast, pressure exerted on another part of the tool guide 14 can cause rotation of the tool guide 14. This intuitive transition from translational control to rotational control is implemented through the combination of the design of the tool guide 14 and the definition of the virtual application point A’ of the forces in the control law. In particular, the practitioner does not need to use a user interface (control pedal 19, dedicated physical button, virtual button on a control screen, or similar) to switch from translational control to rotational control. The torque of the pressure force ? ⃗ exerted on the lever 58 depends not only on the cosine of the angle θ but also on the distance AA’ separating the virtual application point A’ and the real application point A of the pressure force ? ⃗. It is therefore also advantageous to position the virtual application point A’ at a short distance from the support surface of the lever 58 (for example less than five centimeters). It should be noted that other examples of embodiments of the holding system 50 of the tool guide could be compatible with this idea of advantageously positioning the virtual application point A' relative to the pressure force ? ⃗ exerted by the practitioner on the lever 58 of the holding system 50 (for example the embodiment of the holding system described in the patent application WO 2020/201286 A1 with reference to Figures to 6 of this application). The above description clearly illustrates that, through its various features and their advantages, the present invention achieves the set objectives. The proposed solution in fact allows the medical instrument WO 2024/188531 - 30 - PCT/EP2024/052454 to be inserted without deviation from the planned trajectory 41. The approach of the tool guide 14 as close as possible to the patient’s skin in order to perform a partial insertion of the medical instrument 15, then the relocation of the tool guide 14 to the planned insertion position, are easily implemented by the practitioner by virtue of the collaborative axial control mode. The haptic feedback permits an easy and intuitive return to the insertion position. A particular design of the tool guide 14 combined with a particular position of the virtual application point A’ taken into account in the control law also allows an intuitive transition from translational control to rotational control of the tool guide 14. It should be noted that the invention has been described using an optical navigation system. However, there would be nothing to prevent the use, in a variant, of an electromagnetic navigation system instead of the optical navigation system. In this case, the various "markers" detectable by the navigation system (markers present on the patient reference 22, markers present on the tool guide 14) would then correspond to electro-magnetic sensors whose position can be determined by the navigation system in a generated electromagnetic field.

Claims

1. WO 2024/188531 - 31 - PCT/EP2024/052454 Claims 1. A 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), of which a distal end is provided 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) along a planned rectilinear trajectory (41) between an entry point (43) located at the level of the skin of the patient and a target point (44) located within the anatomy of interest (45), the medical robot (10) comprises a control unit (12) configured to control the robotic arm (13) in order to move the tool guide (14), the control unit (12) is configured to determine and memorize an insertion position from the planned trajectory (41), the insertion position corresponding to a placement and an orientation of the tool guide (14) that are to be maintained when the practitioner proceeds to insert the medical instrument as far as the target point, in an “automatic control” mode, the control unit (12) is configured to move the tool guide (14) autonomously to the insertion position, in a “collaborative axial control” mode, the control unit (12) is configured to determine, with the aid of a force sensor (16) coupled to the tool guide (14), a force exerted by the practitioner on the tool guide (14), and to determine a speed of movement of the tool guide (14) as a function of the force thus determined, the movement of the tool guide (14) being constrained in order to authorize only: WO 2024/188531 - 32 - PCT/EP2024/052454 - a movement allowing a translation of the tool guide (14) along the axis of the planned trajectory (41), or - a movement allowing a translation of the tool guide (14) along the axis of the planned trajectory (41) and a rotation of the tool guide (14) about the axis of the planned trajectory (41), in the collaborative axial control mode, the control unit (12) is configured to provide haptic feedback to the practitioner when the tool guide (14) returns to the insertion position.

2. The medical robot (10) as claimed in claim 1, wherein, in the collaborative axial control mode, when the distance between a current position of the tool guide and the insertion position is less than a first threshold, the control unit (12) is configured to calculate a speed of movement of the tool guide (14) as a function of a gain factor applied to the force exerted by the practitioner on the tool guide (14), the value of the gain factor decreasing progressively as a function of the distance between the current position and the insertion position.

3. The medical robot (10) as claimed in either of claims 1 and 2, wherein, in the collaborative axial control mode, when the distance between a current position of the tool guide and the insertion position is less than a second threshold, the control unit (12) is configured to limit or maintain the speed of movement of the tool guide (14) at a predetermined speed regardless of the force exerted by the practitioner on the tool guide (14).

4. The medical robot (10) as claimed in any one of claims 1 to 3, wherein, in the collaborative axial WO 2024/188531 - 33 - PCT/EP2024/052454 control mode, the control unit (12) is configured to prohibit any movement of the tool guide (14) for a predetermined duration when the insertion position is reached.

5. The medical robot (10) as claimed in any one of claims 1 to 4, wherein the tool guide (14) comprises at least one marker (147) detectable by a navigation system (30), and the control unit (12) is configured to: - receive, from said navigation system (30), a first item of information relating to a position of the tool guide (14) in a reference frame of the navigation system (30), - receive, from said navigation system (30), a second item of information relating to an insertion position, in the reference frame of the navigation system (30), that the tool guide (14) has to adopt in order to guide the medical instrument (15) along the planned trajectory (41) until the target point is reached, - determine the insertion position, in a reference frame of the medical robot (10), from the first item of information and the second item of information.

6. The medical robot (10) as claimed in claim 5, wherein the second item of information corresponds to a position, in the reference frame of the navigation system (30), of a patient reference (22) intended to be placed on the patient (20) in proximity to the anatomy of interest, said patient reference (22) comprising at least one marker (221) detectable by the navigation system (30) and at least one radiopaque marker (222), and the control unit (12) is configured to determine the insertion position from the position of the patient reference (22) and from the planned trajectory (41), said WO 2024/188531 - 34 - PCT/EP2024/052454 trajectory (41) being defined relative to the position of the patient reference (22) with the aid of a pre-interventional medical image (40) on which can be seen the anatomy of interest of the patient and said at least one radiopaque marker (222) of the patient reference (22).

7. The medical robot (10) as claimed in any one of claims 1 to 6, wherein the part of the medical instrument (15) intended to penetrate the patient’s body has an axial symmetry along an axis which, during insertion of the medical instrument (15), corresponds to the axis of the planned trajectory, and, in the collaborative axial control mode, the movement of the tool guide (14) is constrained in order to limit it to a movement allowing a translation of the tool guide (14) along the axis of the planned trajectory (41) and a rotation of the tool guide (14) about the axis of the planned trajectory (41).

8. The medical robot (10) as claimed in claim 7, wherein: the tool guide (14) comprises two jaws (51, 55), each jaw comprising a groove (52, 56), the jaws being able to be driven between a closed position, in which the grooves (52, 56) are contiguous and define a guide duct (59) for holding the medical instrument (15) and guiding it in translation, and an open position, in which the grooves (52, 56) are spaced apart from each other for placement or release of the medical instrument (15), the guide duct adopting, at the insertion position, a position coaxial to the planned trajectory, the change from the closed position to the open position being able to be brought about by the practitioner pressing on a lever (58) formed by a support surface of one of the jaws (55), WO 2024/188531 - 35 - PCT/EP2024/052454 in the collaborative axial control mode, the control unit (12) is configured to transpose the force exerted by the practitioner on the tool guide (14) at a virtual application point (A’) positioned such that the axis of a pressure force ( ? ⃗) exerted on the lever (58) and the axis (AA’) passing through a real application point (A) of the pressure force (? ⃗) and the virtual application point (A’) form an angle (θ) of less than twenty degrees.

9. The medical robot (10) as claimed in any one of claims 1 to 8, wherein the robotic arm (13) comprises at least six degrees of freedom.

10. The medical robot (10) as claimed in any one of claims 1 to 9, wherein the control unit (12) is configured to provide a visual indication and/or an acoustic indication when the tool guide (14) returns to the insertion position or when the tool guide (14) goes beyond the insertion position.