Navigation method for positioning a medical robot - Patents.com

Abstract

The present invention relates to an optical navigation system (100) for determining the position of a target anatomical structure of a patient. The system includes a localization device (40) having at least two optical sensors (41) and a patient fiducial (21) having at least three optical markers (26). The system also includes a reflecting device (30). When a line of sight between the patient fiducial and the optical sensor is crossed by an obstacle (60), the optical sensor is configured to measure, for each optical marker of the patient fiducial, a quantity representative of the position of the optical marker within the reference frame of the localization device from optical radiation having a path originating from the optical marker and reflected by the reflecting device to the respective optical sensor.

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention belongs to the field of minimally invasive and non-invasive medical interventions assisted by medical robots. The present invention relates in particular to an optical navigation system for determining the position of a target anatomical structure of a patient in order to optimally position a medical instrument mounted on one end of an articulated arm of a medical robot. In particular, the present invention makes it possible to determine the position of the target anatomical structure even when obstacles prevent the acquisition of a direct line of sight between optical markers located in the target anatomical structure and an optical sensor of the navigation system. The present invention also relates to a method for determining the position of a target anatomical structure of a patient. [Background technology]

[0002] Prior Art Many medical interventions, such as minimally invasive or non-invasive medical interventions, require very precise positioning or movement of a medical instrument (e.g., needle, catheter, electrode, ultrasound generator, drill bit, etc.) relative to a target anatomy of a patient (e.g., liver, lungs, kidneys, spine, etc.). Professionals performing this type of medical intervention can be assisted by a medical robot. In this case, the medical robot positions, maintains and / or guides the medical instrument relative to the target anatomy of the patient by means of a navigation system. The medical instrument is, for example, mounted on one end of an articulated arm of the medical robot. The navigation system makes it possible to determine the position of the medical instrument and the position of the target anatomy. Information about the respective positions of the medical instrument and the target anatomy relative to each other thus allows the medical robot to configure its articulated arm such that the medical instrument is optimally positioned relative to the target anatomy.

[0003] There are different types of navigation systems: Electromagnetic navigation systems have the drawback of being susceptible to interference and distortion of the electromagnetic field in the presence of metallic materials (such as the motors of medical robots); In this sense, optical navigation systems have the drawback of no longer functioning if the line of sight between a marker positioned in the anatomical structure of interest and the optical sensor of the navigation system is blocked by an obstacle (this is the case, for example, when an expert comes between said marker and said optical sensor).

[0004] Generally, it is not sufficient to determine the position of the target anatomy at a preferred time when a direct line of sight is available, because the patient's target anatomy may be moving, for example due to the patient's respiratory movements or the displacement of the anatomy by a specialist. It is therefore necessary to be able to track the position of the target anatomy over time with the aid of the navigation system, even during periods when the line of sight between the markers positioned on the target anatomy and the optical sensor of the navigation system is blocked by obstacles.

[0005] Some solutions in the prior art involve optimizing the positioning of the markers and optical sensors used to reduce the risk that the line of sight is blocked by an obstacle. These solutions are generally complex and do not always allow to guarantee the operation of the optical navigation system when the line of sight is blocked by an obstacle.

[0006] EP 3501443 A1 specifically discloses a system that includes a rotating component integrated into a surgical light to move the camera to a suitable position for aiming at the patient's target anatomical structure when an obstacle prevents obtaining a direct line of sight.

[0007] Some prior art solutions seek to combine an optical navigation system with another complementary navigation system (e.g., an electromagnetic navigation system) that allows the navigation system to ensure operation when the line of sight is blocked by an obstacle, but these solutions result in complex and expensive systems whose accuracy may be affected by the presence of metallic objects. Summary of the Invention [Problem to be solved by the invention]

[0008] Disclosure of the Invention The object of the present invention is to overcome all or some of the drawbacks of the prior art, particularly those mentioned above. [Means for solving the problem]

[0009] To this end and according to a first aspect, the invention provides an optical navigation system for determining the position of a target anatomical structure of a patient. The system specifically comprises a patient fiducial intended to be positioned at the target anatomical structure on the patient, a localization device and a control unit. The localization device comprises at least two optical sensors. The patient fiducial has at least three optical markers. The respective positions of the optical markers of the patient fiducial relative to each other are known a priori by the control unit. The optical navigation system further comprises a reflecting device, the position of which in the reference frame of the localization device can be determined by the control unit. If a direct line of sight between the patient fiducial and the respective optical sensor is available, the optical sensor is configured to measure, for each optical marker of the patient fiducial, a parameter representative of the position of said optical marker in the reference frame of the localization device based on optical radiation coming from said optical marker and having, for each optical sensor, a direct path between said optical marker and said optical sensor. When a direct line of sight between the patient fiducial and the optical sensor is interrupted by an obstacle, the optical sensor is configured to measure, for each optical marker of the patient fiducial, a parameter representative of the position of said optical marker in the reference frame of the localization device based on optical radiation having a path coming from said optical marker and being reflected by a reflecting device towards the respective optical sensor. The control unit is configured to determine the position of the patient fiducial in the reference frame of the localization device from the measurements performed by the optical sensor and to estimate therefrom the position of the anatomical structure of interest in said reference frame.

[0010] In this application, "optical radiation" is understood to mean electromagnetic radiation in the wavelength range of 100 nm (100 nanometers) to 1 mm (1 millimeter). Thus, infrared radiation, visible light radiation and ultraviolet radiation are optical radiation. The term "light ray" is sometimes used to define the particular path that optical radiation follows.

[0011] In this application, the term "position" refers to position and orientation in the three dimensions of a spatial reference frame.

[0012] The expression "the position of the reflecting device can be determined by the control unit" means that the position of the reflecting device is known a priori by the control unit (e.g., the position of the reflecting device is stored in a memory of the control unit) or it can otherwise be determined by the control unit (e.g., with the aid of an optical marker configured on the reflecting device).

[0013] With such a configuration, the optical navigation system according to the present invention is able to determine the position of a patient's target anatomical structure even when the line of sight is blocked by an obstacle (e.g., a specialist who has to perform a medical intervention on the target anatomical structure or a medical robot assisting said specialist).

[0014] In particular embodiments, the invention may further comprise one or more of the following features, taken alone or in all technically possible combinations:

[0015] In a particular embodiment, the reflector comprises at least three optical markers, the respective positions of the optical markers of the reflector relative to one another being known a priori by the control unit.

[0016] In a particular embodiment, during the period when a direct line of sight between the patient fiducials and the respective optical sensor is available, the control unit is configured to estimate the movement traversed by the patient fiducials in the reference frame of the localization device during the patient's respiratory cycle. Thus, at the time when a direct line of sight between the patient fiducials and the optical sensors is no longer available, the control unit is configured to determine the position of the patient fiducials as a function, on the one hand, of the measurements performed by the optical sensors based on the optical radiation coming from the optical markers of the patient fiducials and reflected by the reflecting device, and on the other hand, of the estimated movement of the patient fiducials.

[0017] In certain embodiments, the patient fiducial further comprises at least three radiopaque markers, the respective positions of which relative to one another are known a priori by the control unit.

[0018] In certain embodiments, the position of the target anatomical structure within the reference frame of the localization device is determined as a function of the position of the patient fiducial within said reference frame and as a function of a medical image of the target anatomical structure of the patient in which the radiopaque markers of the patient fiducial are visible.

[0019] In certain embodiments, the position of the target anatomy within the frame of reference of the localization device is further determined as a function of a biomechanical model of the target anatomy.

[0020] In a particular embodiment, the optical navigation system has three orthogonal reflectors in pairs.

[0021] In a particular embodiment, the optical navigation system further comprises a robot fiducial intended to be positioned at the distal end of the articulated arm of the medical robot. The robot fiducial comprises at least three optical markers. The respective positions of the optical markers relative to one another are known a priori by the control unit. If a direct line of sight between the robot fiducial and the respective optical sensor is available, the optical sensor of the localization device is configured to measure, for each optical marker of the robot fiducial, a parameter representative of the position of said optical marker in the reference frame of the localization device based on an optical radiation coming from said optical marker and having, for each optical sensor, a direct path between said optical marker and said optical sensor. If the direct line of sight between the robot fiducial and the optical sensor is interrupted by an obstacle, the optical sensor is configured to measure, for each optical marker of the robot fiducial, a parameter representative of the position of said optical marker in the reference frame of the localization device based on an optical radiation coming from said optical marker and having a path reflected by a reflecting device towards the respective optical sensor. The control unit is configured to determine the position of the robot reference in the reference frame of the localization device from the measurements thus performed by the optical sensor.

[0022] In a particular embodiment, the optical navigation system further comprises a medical robot including an articulated arm. The robotic fiducial is positioned at a distal end of the articulated arm. The medical robot further comprises an articulated encoder of the articulated arm that allows a position of the robotic fiducial in the reference frame of the medical robot to be determined at any instant in time. The medical robot is configured to transmit the position of the robotic fiducial in the reference frame of the robot to a control unit. The control unit is then configured to estimate a position of a medical instrument mounted on the distal end of the articulated arm of the medical robot relative to a target anatomy of a patient.

[0023] In a particular embodiment, the patient-based and / or robot-based optical markers are active markers, and the optical radiation coming from the optical markers is infrared radiation generated by said optical markers.

[0024] In certain embodiments, the patient-based and / or robot-based optical markers are passive markers, and the optical radiation coming from the optical markers is infrared radiation generated by a localization device and reflected by said optical markers.

[0025] According to a second aspect, the invention relates to a method for determining the position of a target anatomical structure of a patient during a surgical intervention. The method is implemented by an optical navigation system comprising a patient fiducial intended to be positioned at the target anatomical structure on the patient and also a localization device. The respective positions of the optical markers relative to each other are known a priori. The localization device comprises at least two optical sensors. The patient fiducial comprises at least three optical markers. The optical navigation system further comprises a reflecting device, the position of which in the reference frame of the localization device is known. The method comprises: - if a direct line of sight between the patient fiducial and the respective optical sensor is available, measuring, for each optical marker of the patient fiducial, a parameter representative of the position of said optical marker in the reference frame of the localization device based on the optical radiation coming from said optical marker and, for each optical sensor, having a direct path between said optical marker and said optical sensor; - if a direct line of sight between the patient fiducial and the optical sensor is interrupted by an obstacle, measuring, for each optical marker of the patient fiducial, a parameter representative of the position of said optical marker in the reference frame of the localization device based on optical radiation having a path coming from said optical marker and being reflected by a reflecting device towards the respective optical sensor, - determining the position of the patient fiducials in the frame of reference of the localization device from the measurements thus performed by the optical sensor, - determining a position of the anatomical structure of interest within said frame of reference of a localization device based on the position of a patient reference; has.

[0026] It should be noted that the location of the target anatomical structure of the patient and the positioning of the medical instrument mounted on one end of the articulated arm of the medical robot occur prior to the performance of the medical operation by the specialist, and therefore the method according to the invention for determining the location of the target anatomical structure of the patient does not include the step of therapeutic or surgical treatment.

[0027] In particular embodiments, the invention may further comprise one or more of the following features, taken alone or in all technically possible combinations:

[0028] In certain embodiments, the method comprises: - estimating the movement traversed by the patient fiducial in the frame of reference of the localization device during the patient's respiratory cycle during the period when a direct line of sight between the patient fiducial and the respective optical sensor is available; - determining the position of the patient fiducial as a function of measurements carried out by the optical sensor on the one hand based on optical radiation coming from the optical markers of the patient fiducial and reflected by the reflecting device, and on the other hand as a function of an estimated movement of the patient fiducial, at a time when a direct line of sight between the patient fiducial and the optical sensor is no longer available. It further has:

[0029] In certain embodiments, determining the position of the target anatomy within the reference frame of the localization device is further performed based on a medical image of the target anatomy of the patient, in which the patient fiducial radiopaque markers are visible.

[0030] In certain embodiments, determining the position of the target anatomy within the reference frame of the localization device is further performed based on a biomechanical model of the target anatomy.

[0031] In a particular embodiment, the optical navigation system further comprises a robotic fiducial intended to be positioned at a distal end of an articulated arm of a medical robot, the robotic fiducial comprising at least three optical markers, the respective positions of which relative to one another being known a priori. - if a direct line of sight between the robot fiducial and the respective optical sensor is available, measuring, for each optical marker of the robot fiducial, a parameter representative of the position of said optical marker in the reference frame of the localization device based on the optical radiation coming from said optical marker and, for each optical sensor, having a direct path between said optical marker and said optical sensor; - measuring, for each optical marker of the robot fiducial, a parameter representative of the position of said optical marker in the reference frame of the localization device based on optical radiation having a path coming from said optical marker and being reflected by a reflecting device towards the respective optical sensor, if the direct line of sight between the robot fiducial and the optical sensor is interrupted by an obstacle; - determining the position of the robot reference in the reference frame of the localization device based on the measurements thus performed by the optical sensor. It further has:

[0032] In a particular embodiment, the optical navigation system further comprises a medical robot having an articulated arm at the distal end of which a robotic datum is positioned. The medical robot also has an articulated encoder on the articulated arm that allows determining the position of the robotic datum within the reference frame of the medical robot at any instant in time. Thus, the method includes determining the position of a medical instrument mounted on the distal end of the articulated arm of the medical robot relative to the target anatomy of the patient.

[0033] Figure presentation The invention will be better understood on reading the following description, given by way of non-limiting example and made with reference to FIGS. [Brief description of the drawings]

[0034] [Figure 1] FIG. 2 is a schematic diagram of an optical navigation system according to the present invention when a direct line of sight is available. [Diagram 2] 2 is a schematic diagram of an optical navigation system according to the present invention when the line of sight is blocked by an obstacle; [Diagram 3] FIG. 1 is a schematic diagram of a patient fiducial having three optical and three radiopaque markers. [Figure 4] FIG. 1 is a schematic diagram of a robotic fiducial with three optical markers. [Diagram 5] FIG. 1 is a schematic diagram of a reflector device having four optical markers. [Figure 6] 13 is a schematic diagram of the determination of the position of a patient-based optical marker when the line of sight is interrupted by an obstacle, as a function of measurements performed by an optical sensor on a light beam reflected by a reflecting device. [Figure 7] 1 is a schematic diagram of the main steps of a method for determining the location of an anatomical structure of interest within a patient. [Figure 8] FIG. 2 is a schematic diagram of the estimated movement of a patient reference during the patient's respiratory cycle. [Figure 9a] FIG. 13 is a schematic diagram of the determination of the position of an optical marker of a patient reference when the line of sight is interrupted by an obstacle, as a function of the measurements performed by the optical sensor and as a function of the estimated movement of the patient reference. [Figure 9b] FIG. 9b is a cross-sectional view of FIG. 9a. [Figure 10] 1 is a schematic diagram of the main steps of a particular embodiment of a method for determining the location of an anatomical structure of interest within a patient. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] In the figures, identical reference numbers between the figures designate identical or similar elements. For reasons of clarity, elements shown are not necessarily drawn to scale unless otherwise indicated.

[0036] Detailed Description of an Embodiment of the Invention FIG. 1 illustrates generally one example of an optical navigation system 100 according to the present invention.

[0037] In the example of the subject shown in Fig. 1, the optical navigation system 100 comprises the main elements: a localization device 40, a control unit 43, a patient fiducial 21 intended to be positioned in the anatomical structure of interest of a patient 20, and a reflecting device 30. In the example shown in Fig. 1, the patient 20 lies on a table 50 in an operating room.

[0038] The objective of the optical navigation system 100 is to determine the position of the patient fiducials 21 in order to estimate therefrom the position of the anatomical structure of interest in the reference frame of the localization device 40. For this purpose, the control unit 43 is configured to implement all or some of the steps of a method allowing the determination of the position of the patient fiducials in the reference frame of the localization device 40. The control unit 43 comprises, for example, one or more processors and a memory (magnetic hard disk, electronic memory, optical disk, etc.) in which a computer program product is stored in the form of a set of program code instructions that are executed to implement the different steps of such a method. Alternatively or additionally, the control unit 43 comprises one or more programmable logic circuits (FPGA, PLD, etc.), and / or one or more specialized integrated circuits (ASICs), and / or a set of discrete electronic components suitable for implementing all or some of the method steps, etc.

[0039] As shown in Fig. 1, the optical navigation system 100 may also include a robot datum 11 intended to be positioned at the distal end of the articulated arm 13 of the medical robot 10, for example on an instrument holder 14 mounted at said end. The control unit 43 may therefore also be configured to determine the position of the robot datum in the reference frame of the localization device 40. If the position of the medical instrument mounted at the level of the instrument holder 14 relative to the position of the robot datum 11 is known by the control unit 43, the control unit 43 may determine the position of the medical instrument in the reference frame of the localization device 40. The respective positions of the medical instrument and the target anatomy relative to each other may thus enable the medical robot 10 to configure its articulated arm such that the medical instrument is optimally positioned with respect to the target anatomy.

[0040] The control unit 43 can be integrated in the localization device 40, as in the example shown in FIG. 1. The control unit 43 can also be a separate entity from the localization device 40 or else integrated in the medical robot 10. If the control unit 43 is not integrated in the medical robot 10, it can be configured to transmit information regarding the position of the target anatomy and / or the position of the medical instrument to the medical robot 10, so that the medical robot 10 can configure its articulated arm 13 such that the medical instrument is optimally positioned with respect to the target anatomy. This transmission of information can be performed, for example, via wireless communication means. If the control unit 43 is not integrated in the localization device 40, it is configured to receive information regarding the position of the patient fiducials 21 and / or the robot fiducials 11 from the localization device 40. The transmission of information between the localization device 40 and the control unit 43 can be performed, for example, via wireless communication means.

[0041] Fig. 3 shows a schematic representation of the patient fiducial 21. The patient fiducial 21 has at least three optical markers 26 such that the position of the patient fiducial 21 can be determined in three spatial dimensions of the reference frame of the localization device 40. The respective positions of the optical markers 26 of the patient fiducial 21 relative to one another are known a priori by the control unit 43. Advantageously, the geometric shape of the respective optical markers 26 may also be known a priori by the control unit 43. In the example shown in Fig. 3, the patient fiducial 21 has three optical markers 26 of spherical shape. The spherical shape allows for an optimization of the reflection of the optical radiation.

[0042] The optical markers 26 can be passive or active. Passive optical markers reflect, for example, optical radiation emitted by another element of the localization device 40. Passive optical markers can correspond, for example, to reflective spheres detectable by an infrared stereo camera (such as those used in the Polaris® navigation system manufactured by Northern Digital Inc.) or black and white patterns visible by a stereo camera (such as those used in the MicronTracker® navigation system from ClaroNav). Active optical markers themselves emit optical radiation, for example infrared radiation, detectable by the localization device 40.

[0043] Fig. 4 shows the robotic fiducial 11 in a schematic way. The robotic fiducial 11 has at least three optical markers 16 so that the position of the robotic fiducial 11 can be determined in three spatial dimensions of the reference frame of the localization device 40. The respective positions of the optical markers 16 of the robotic fiducial 11 relative to each other are known a priori by the control unit 43. Advantageously, the geometric shape of the respective optical markers 16 may also be known a priori by the control unit 43. In the example shown in Fig. 4, the robotic fiducial 11 has three optical markers 16 of spherical shape. What has been described above with regard to the active or passive nature of the optical markers 26 of the patient fiducial 21 also applies to the optical markers 16 of the robotic fiducial 11.

[0044] The respective positions of the optical markers 16 of the robot fiducial 11 relative to each other are different from the respective positions of the optical markers 26 of the patient fiducial 21 relative to each other. Such an arrangement allows the localization device 40 to distinguish between the patient fiducial 21 and the robot fiducial 11.

[0045] As shown in Fig. 1, the localization device 40 has at least two optical sensors 41, which correspond for example to the two sensors of a stereo camera operating in an infrared radiation field or in a visible light field. In the remainder of the description, by way of non-limiting example, it is considered that the optical sensors 41 of the localization device 40 and the various optical markers 16, 21 of the optical navigation system 100 are designed to operate with infrared type optical radiation, i.e. electromagnetic radiation whose wavelength varies between 780 nm and 1 mm. However, it should also be noted that the optical navigation system 100 according to the invention can also be designed to operate in a visible light field (electromagnetic radiation whose wavelength varies between 380 nm and 780 nm) or in an ultraviolet radiation field (electromagnetic radiation whose wavelength varies between 10 nm and 380 nm).

[0046] In a conventional manner and as shown in FIG. 1, if a direct line of sight is available between the patient fiducial 21 and the optical sensor 41 of the localization device 40 (i.e. if there are no obstacles between the patient fiducial 21 and the optical sensor 41 of the localization device 40 or in other words if the infrared radiation can propagate a direct path 22 as a straight line between each optical marker 26 of the patient fiducial 21 and each optical sensor 41 of the localization device 40), the position of each optical marker 26 can be determined as a function of the travel time of the infrared radiation corresponding to the direct path 22 between the optical marker 26 and the optical sensor 41 (the speed of infrared radiation is known since this is equal to the speed of light) and / or as a function of the angle of arrival of the infrared radiation at the optical sensor 41.

[0047] For example, if the optical markers 26 used in the optical navigation system 100 are passive markers, the optical sensor 41 may be configured to emit infrared radiation. This infrared radiation is then reflected by the various optical markers 26 towards the optical sensor 41. The optical sensor 41 is configured to receive this reflected infrared radiation. The distance between the optical markers 26 and the optical sensor 41 is therefore equal to half the time required by the infrared radiation to perform a round trip between the optical sensor 41 and the optical markers 26 multiplied by the speed of light. Knowing the distance between each optical marker 26 and each optical sensor 41, and knowing a priori the configuration of the optical markers 26 relative to each other on the patient fiducial 21, the position of the patient fiducial 21 in the frame of reference of the localization device 40 can be determined.

[0048] According to another example, if the optical markers 26 used in the optical navigation system 100 are active markers, each optical sensor 41 is configured to determine the angle of arrival at said optical sensor 41 of infrared radiation generated directly by the optical marker 26. By knowing the angle of arrival at the respective optical sensor 41 for each optical marker 26, and knowing a priori the configuration of the optical markers 26 relative to each other on the patient fiducial 21, the position of the patient fiducial 21 within the frame of reference of the localization device 40 can be determined.

[0049] Similarly, the localization device 40 can determine the position of the robot fiducial 11 within the reference frame of the localization device 40 if a direct line of sight is available between the robot fiducial 11 and the optical sensor 41 of the localization device 40 .

[0050] It should be possible to determine the position of the target anatomy of the patient from the position of the patient fiducial 21. For this purpose and as shown in FIG. 3, the patient fiducial 21 may have radiopaque markers 27. The respective positions of the radiopaque markers 27 relative to one another are known a priori by the control unit 43. Advantageously, the geometric shape of the radiopaque markers 27 may also be known a priori by the control unit 43. Preferably, the patient fiducial 21 has at least three radiopaque markers 27. The position of the target anatomy in the reference frame of the localization device 40 can therefore be determined as a function of the position of the patient fiducial 21 in said reference frame and as a function of a medical image of the target anatomy of the patient, in which the radiopaque markers 27 of the patient fiducial 21 are visible. In fact, the medical image gives information about the position of the target anatomy relative to the position of the patient fiducial 21. Thus, by knowing the position of the patient fiducial 21 in the reference frame of the localization device 40, the position of the target anatomy in this reference frame can be deduced therefrom.

[0051] For example, the radiopaque marker 27 can be a ceramic or metal ball that is visible in a medical image (e.g., computed tomography, 3D rotational angiography, magnetic resonance imaging, ultrasound, etc.). A medical image of the patient 20 is acquired together with the patient fiducials 21. This medical image can be registered with another image of the same patient that was previously acquired and includes intervention planning data, or can be used directly to plan the intervention. The planned intervention can be the ablation (e.g., by radiofrequency, microwave, electroporation, laser, cryotherapy, ultrasound) of a tumor in the target anatomical structure (e.g., liver, lung or kidney). The planned intervention can also be the insertion of a medical instrument into the brain, into the spine (e.g., for vertebroplasty and bone cement therapy) or into another bone structure (e.g., knee). The planning includes determining the path that the medical instrument (e.g., needle) will follow between an entry point in the patient's skin and a target point (in the tumor) in the target anatomical structure. Once the position of the target anatomical structure of the patient has been determined in the frame of reference of the localization device, it is possible to deduce from these planning data the position that the medical instrument must occupy in this frame of reference.

[0052] As shown in FIG. 2, a problem arises in determining the position of the patient fiducial 21 if an obstacle 60 blocks the line of sight between the patient fiducial 21 and the sensor 41 of the localization device 40 (and a similar problem arises in determining the position of the robot fiducial 11 if an obstacle intersects the line of sight between the robot fiducial 11 and the sensor 41 of the localization device, although not shown in FIG. 2).

[0053] To overcome this problem, the invention proposes to use a reflecting device 30 whose position in the reference frame of the localization device 40 is known by the control unit 43 .

[0054] The position of the reflecting device 30 is for example known a priori and stored in the memory of the control unit 43. In one variant and as shown in Fig. 5, the reflecting device 30 has at least three optical markers 36. The respective positions of the optical markers 36 relative to one another are known a priori by the control unit 43. Advantageously, the geometric shape of each optical marker 36 may also be known a priori by the control unit 43. The position of the reflecting device 30 can thus be determined by the control unit 43 with the aid of the optical sensor 41 of the localization device 40. As shown in Figs. 1 and 2, the reflecting device 30 is for example fixed to an intervention table 50 and the position of the reflecting device 30 is not changed during the period of time required to determine the anatomical structure of interest of the patient.

[0055] The reflector 30 corresponds, for example, to a glass plate on top of which is glued a thin sheet of metal (for example aluminum or silver), itself covered by a layer of copper or lead. Alternatively, the glass plate can be covered by a thin gold foil. The reflector 30 can be a flat mirror or a concave mirror that allows concentrating infrared radiation. In the example in question, the reflector 30 is a flat mirror of rectangular shape. As shown in FIG. 5, optical markers 36 can be positioned at each corner of the rectangle formed by the reflector 30.

[0056] 2 and 6, when the direct line of sight between the patient fiducial 21 and the optical sensor 41 is blocked by an obstacle 60, the optical sensor 41 is configured to measure, for each optical marker 26 of the patient fiducial 21, a parameter representative of the position of said optical marker 26 in the reference frame of the localization device 40 based on infrared rays coming from said optical marker 26 and following a path 23 reflected by the reflecting device 30 towards the respective optical sensor 41 (and not based on infrared rays corresponding to a direct path 22 between said optical marker 26 and said optical sensor 41). The expression "parameter representative of the position of the marker" is understood to mean, for example, the travel time of the infrared rays between the optical sensor and the optical marker or the angle of arrival of the infrared rays at the optical sensor 41.

[0057] For example and as shown in FIG. 6, if the angle of arrival of the infrared ray 23 reflected by the reflecting device 30 and coming from the optical marker 26 of the patient reference 21 is known for each optical sensor 41 and the position of the reflecting device 30 is known, the position of said optical marker 26 can be determined. It should be noted that the infrared ray 23 is reflected in the reflecting device 30 at the reflection point 28 by making a reflection angle θ with respect to a line δ perpendicular to the reflecting device 30 and passing through the reflection point 28. This reflection angle θ is the same for the incident ray and the reflected ray. In FIG. 6, the angle of arrival of the infrared ray 23 at the optical sensor 41 in the plane containing the infrared ray 23 and the line δ corresponds to the angle φ. If the angle of arrival φ at the optical sensor 41 and the position of the reflecting device 30 are known, it is possible to determine the value of the reflection angle θ. Thus, the reflection angle can be determined for the infrared ray associated respectively with each of the two optical sensors 41. The position of the optical marker 26 corresponds to the intersection point of the two infrared rays.

[0058] It should be noted that the position of the optical marker 26 can also be determined from the optical sensor 41, on the one hand as a function of the angle of arrival of the infrared ray 23, and on the other hand as a function of the travel time of the infrared ray 23 between the optical marker 26 and the optical sensor 41 (assuming that this travel time can be determined).

[0059] FIG. 7 shows diagrammatically the main steps of a method implemented by the control unit 43 for determining the position of a target anatomical structure of a patient.

[0060] The method 200 includes a first step in which it is detected whether an obstacle interrupts the direct line of sight between the patient fiducial 21 and the optical sensor 41 of the localization device 40 .

[0061] If a direct line of sight is available (no obstacles are present), the method 200 includes a step 201 in which a measurement is performed by the optical sensor 41 based on infrared light following a direct path 22 between the optical marker 26 of the patient reference 21 and the optical sensor 41.

[0062] If the line of sight is blocked (an obstacle is present), the method 200 includes a step 202 in which a measurement is performed by the optical sensor 41 based on infrared light 23 following an indirect path between the optical marker 26 of the patient reference 21 and the optical sensor 41, including reflection on the reflecting device 30.

[0063] In step 203 , the position of the patient fiducial 21 is determined from the position of the optical marker 26 determined based on measurements performed by the optical sensor 41 .

[0064] In step 204 , the position of the target anatomical structure 204 is determined from the position of the patient fiducials 21 .

[0065] The optical sensor 41 is configured by default to function with infrared radiation 23 coming directly from the workspace in which, for example, the patient fiducial 21 and / or the robot fiducial 11 are assumed to be located. If no such infrared radiation is detected, the control unit 43 configures the optical sensor 41 to function based on infrared radiation 23 reflected by the reflecting device 30.

[0066] Thus, the location of a patient's target anatomy can be determined at any time even when a direct line of sight is not available.

[0067] What has been described above in relation to determining the position of the patient fiducial 21 also applies to determining the position of the robot fiducial 11 when an obstacle interrupts the line of sight between the robot fiducial 11 and the sensor 41 of the localization device 40 .

[0068] In a particular embodiment, the medical robot 10 further comprises an articulated encoder, which makes it possible to determine at any instant in time the position of the robot fiducial 11 in the reference frame of the medical robot 10, at the level of its articulated arm 13. The medical robot 10 is configured to transmit the position of the robot fiducial 11 in the reference frame of the medical robot 10 to the control unit 43. The control unit 43 is then configured to estimate the position of the medical instrument mounted at the distal end of the articulated arm 13 of the medical robot 10 with respect to the target anatomical structure of the patient 20.

[0069] For this purpose, for example in a preliminary setup step, it can be envisaged that the articulated arm 13 of the medical robot 10 executes predefined movements in order for the robotic fiducial 11 to occupy different calibration positions distributed in the common working space of the medical robot 10 and the optical navigation system 100. For each calibration position occupied by the robotic fiducial 11, the control unit 43 receives position information from the articulated encoders on the one hand and from the optical markers 16 of the robotic fiducial 11 on the other hand. The reference frames of the medical robot 10 and of the localization device 40 can be realigned by matching the different calibration positions and calculating the rigid body registration point by point.

[0070] As a patient breathes, the patient's target anatomy (and more specifically the target zone within the target anatomy) follows the respiratory movement. With the aid of the optical navigation system 100, it should be possible to track the position of the target anatomy over time, even during periods when the line of sight between the markers positioned on the target anatomy and the optical sensor of the navigation system is blocked by an obstacle.

[0071] 8 shows diagrammatically the movement of the patient fiducial 21 over a period of time comprising several respiratory cycles of the patient. The movement is shown in a system having two coordinates x and y. Each axis x or y thus corresponds to a component of the movement of the patient fiducial 21.

[0072] For example, during a time period of interest, a direct line of sight is always available between the patient fiducial 21 and the optical sensor 41 of the localization device 40. The position of each optical marker 26 of the patient fiducial 21 is determined at several points during that time period. Thus, an estimated movement 24 can be determined, which corresponds to an average movement of the patient fiducial 21, for example for the two selected components, during the patient's respiratory cycle, over the time period of interest. In the remainder of the description, for the sake of clarity, the estimated movement 24 of the patient fiducial 21 is considered to be substantially identical to the movement traversed by each optical marker 26 of the patient fiducial 21. In fact, each optical marker 26 of the patient fiducial 21 may have a specific movement, and thus the movement of the patient fiducial may correspond to the result of the movement of the various optical sensors (it would therefore be conceivable to consider an estimated movement for each optical marker 26 of the patient fiducial 21).

[0073] Figures 9a and 9b show diagrammatically how the position of an optical marker 26 of a patient fiducial 21 can be determined as a function of the estimated movement 24 of said optical marker 26 when the line of sight is blocked by an obstacle. Figure 9b is a two-dimensional representation of Figure 9a in a plane containing infrared radiation 23 coming from the optical marker 26 and reflected by a reflecting device 30, and also a line δ perpendicular to the reflecting device 30 and passing through the reflecting point 28.

[0074] As shown in Figures 9a and 9b, when the line of sight is no longer available between the patient fiducial 21 and the optical sensor 41, the position of the optical marker 26 can be determined on the one hand as a function of the measurements performed by the optical sensor 41 on the basis of the light ray 23 coming from said optical marker 26 of the patient fiducial 21 and reflected by the reflecting device 30, and on the other hand as a function of the estimated movement 24 of the optical marker 26. As shown in Figure 9b, the estimated movement 24 of the optical marker 26 is resolved into two orthogonal components x and y belonging to a plane containing the infrared ray 23 and the line δ. The infrared ray 23 is reflected in the reflecting device 30 at the reflection point 28, thereby forming a reflection angle θ with respect to the line δ. This reflection angle θ is identical for the incident and reflected light ray. The infrared ray 23 forms an arrival angle φ at the optical sensor 41.

[0075] If the angle of arrival φ at the optical sensor 41 and the position of the reflecting device 30 are known, the value of the reflection angle θ can be determined. It is therefore possible to determine the position of the optical marker 26, since this corresponds to the intersection of the infrared light 23 with the path followed by the estimated movement 24 of the optical marker 26.

[0076] According to another example, if the travel time of the infrared ray 23 between the optical marker 26 and the optical sensor 41 is known, in other words if the distance traveled by said infrared ray is known, it is also possible to determine the position of the optical marker 26, since there is only a single point on the path traced by the estimated movement 24 of the optical marker 26 from which the infrared ray 23 reflected on the reflecting device 30 travels said distance and then reaches the optical sensor 41.

[0077] Once the position of each optical marker 26 has been determined, the position of the patient fiducials 21 can also be determined. Thus, the position of the target anatomical structure can be deduced therefrom, particularly if the position of the target anatomical structure can be defined relative to the position of the patient fiducials on the medical image.

[0078] It is further possible to use a biomechanical model of the target anatomy in order to optimize the determination of the position of the target anatomy as a function of the position of the patient fiducial 21 and the estimated movement 24 followed by the patient fiducial 21. Indeed, in the form of a biomechanical model it is possible to model the deformations of the various anatomical structures (muscles, tendons, bone structures, organs, vascular networks, etc.) and the mechanical interactions between these various structures. The biomechanical model may therefore make it possible to better define the movements followed by the target anatomy as a function of the movements followed by the patient fiducial 21.

[0079] Figure 10 shows in a schematic way a particular embodiment of the method 200 described with reference to figure 7. In particular, the step 201 of measuring the position of the optical marker 26 of the patient fiducial with a direct line of sight is repeated at several different points in time during a period of time including at least one respiratory cycle of the patient. As described above with reference to figure 8, this allows to estimate in step 205 the movement of the patient fiducial 21 in the respiratory cycle of the patient. This estimated movement 24 is then used in step 203 to determine the position of the patient fiducial 21 when the line of sight is no longer available (as described above with reference to figures 9a and 9b). Thus, in step 204, the position of the target anatomical structure of the patient can be determined from the position of the patient fiducial 21.

[0080] Thus, the present invention makes it possible to determine the position of a patient's target anatomical structure with the aid of the optical navigation system 100 even when a direct line of sight is not available between the patient fiducial 21 and the optical sensor 41 of the localization device 40 of the optical navigation system 100.

[0081] In a particular embodiment and as shown in Figs. 1 and 2, the localization device 40 may further comprise a camera 42 that provides images to the control unit 43 in order to determine the insertion depth of the medical instrument during the intervention. Images of the intervention are continuously taken by the camera 42. When the medical robot 10 is positioned relative to the patient according to the intervention plan, the specialist inserts a medical instrument (e.g. a needle) into the target anatomical structure of the patient in order to reach a target zone (e.g. a tumor). The images from the camera 42 are analyzed by the control unit 43 configured to detect the medical instrument. By knowing the total length of the medical instrument and the position of the reached target zone, the control unit 43 is able to determine the insertion depth of the medical instrument and when the instrument has reached the target zone. When the target zone has been reached, a message is displayed for the specialist's attention, for example on a control screen. The message may be accompanied by an acoustic signal.

[0082] In a particular embodiment, the images provided by the camera 42 of the localization device 40 are analyzed by the control unit 43 in order to recognize gestures performed by the (gloved or not) hand of the expert, said gestures being associated with specific commands intended for the medical robot 10 (for example to configure the articulated arms of the medical robot in a predefined position, to move the base of the medical robot to a predefined position, to urgently interrupt any movement of the medical robot, etc.). The gestures performed by the expert may disturb the line of sight between the patient fiducial 21 and the optical sensor 41, but the reflecting device 30 nevertheless allows the optical navigation system 100 according to the invention to determine the position of the patient fiducial 21.

[0083] It should be noted that several reflectors 30 can be used to increase the number of different paths followed by the optical radiation coming from the optical marker. In a particular embodiment, the optical navigation system 100 advantageously has three different reflectors arranged orthogonally in pairs. If a direct line of sight is not available, the position of the patient fiducial 21 can be determined from the light beam reflected by one or more of the reflectors.

Claims

1. 1. An optical navigation system (100) for determining a position of an anatomical structure of interest in a patient (20), comprising: A location determination device (40) having at least two optical sensors (41), A control unit (43), and A patient fiducial (21) having at least three optical markers (26), the respective positions of which relative to one another are known a priori by the control unit (43), and the patient fiducial (21) is positioned on the patient (20) to the anatomical structure of interest. An optical navigation system (100) comprising: a reflecting device (30), the position of which in a reference frame of the localization device (40) can be determined by the control unit (43), if the control unit (43) determines based on an angle of arrival of optical radiation at each optical sensor (41) coming from the optical marker (26) that a direct line of sight between the patient fiducial (21) and the respective optical sensor (41) is available, the optical sensor (41) is configured to measure, for each optical marker (26) of the patient fiducial (21), a parameter representative of a position of the optical marker (26) within the reference frame of the localization device (40) based on optical radiation coming from the optical marker (26) and having, for each optical sensor (41), a direct path (22) between the optical marker (26) and the optical sensor (41); if the control unit (43) determines, based on an angle of arrival of optical radiation at each optical sensor (41) coming from the optical marker (26), that a direct line of sight between the patient fiducial (21) and the optical sensor (41) is interrupted by an obstacle (60), the optical sensor (41) is configured to measure, for each optical marker (26) of the patient fiducial (21), a parameter representative of the position of the optical marker (26) within the reference frame of the localization device (40) based on optical radiation coming from the optical marker (26) and having a path (23) reflected by the reflecting device (30) towards the respective optical sensor (41), The optical navigation system (100) is characterized in that the control unit (43) is configured to determine the position of the patient fiducial (21) in the reference frame of the localization device (40) from the measurements performed by the optical sensor (41), and to estimate the position of the target anatomical structure in the reference frame from the position of the patient fiducial (21).

2. 2. The optical navigation system (100) of claim 1, wherein the reflecting device (30) has at least three optical markers (36), the respective positions of the optical markers (36) relative to one another being known a priori by the control unit (43).

3. The control unit (43) estimating the movement (24) followed by said patient fiducials (21) within the reference frame of said localization device (40) during a respiratory cycle of said patient (20) during a period when a direct line of sight between said patient fiducials (21) and the respective optical sensors (41) is available; determining the position of the patient fiducial (21) as a function of the measurements performed by the optical sensor (41) on the one hand based on the optical radiation coming from the optical markers (26) of the patient fiducial (21) and reflected by the reflecting device (30) and as a function of the estimated movement (24) of the patient fiducial (21) at a time when a direct line of sight between the patient fiducial (21) and the optical sensor (41) is no longer available; The optical navigation system (100) of claim 1 or 2, configured to:

4. The optical navigation system (100) of any one of claims 1 to 3, wherein the patient reference (21) further comprises at least three radiopaque markers (27), the respective positions of the radiopaque markers (27) relative to one another being known a priori by the control unit (43).

5. 5. The optical navigation system (100) of claim 4, wherein the position of the target anatomical structure within the reference frame of the localization device (40) is determined as a function of the position of the patient fiducial (21) within the reference frame and as a function of a medical image of the target anatomical structure of the patient in which the radiopaque markers (27) of the patient fiducial (21) are visible.

6. 6. The optical navigation system (100) of claim 5, wherein the position of the target anatomical structure within the reference frame of the localization device (40) is further determined as a function of a biomechanical model of the target anatomical structure, the biomechanical model being configured to model deformations of the anatomical structures and mechanical interactions between the anatomical structures.

7. The optical navigation system (100) according to any one of claims 1 to 6, comprising three reflecting devices (30) arranged in orthogonal pairs.

8. a robotic datum (11) intended to be positioned at the distal end of an articulated arm (13) of the medical robot (10), said robotic datum (11) comprising at least three optical markers, the respective positions of said optical markers (16) relative to one another being known a priori by said control unit (43); if the control unit (43) determines based on an angle of arrival of optical radiation at each optical sensor (41) coming from the optical marker (26) that a direct line of sight between the robot reference (11) and the respective optical sensor (41) is available, the optical sensor (41) is configured to measure, for each optical marker (16) of the robot reference (11), a parameter representative of a position of the optical marker (16) within the reference frame of the localization device (40) based on optical radiation coming from the optical marker (16) and having, for each optical sensor (41), a direct path between the optical marker and the optical sensor (41); if the control unit (43) determines based on an angle of arrival of optical radiation at each optical sensor (41) coming from the optical marker (26) that a direct line of sight between the robot reference (11) and the optical sensor (41) is interrupted by an obstacle, the optical sensor (41) is configured to measure, for each optical marker (16) of the robot reference (11), a parameter representative of the position of the optical marker (16) within the reference frame of the localization device (40) based on optical radiation having a path coming from the optical marker (16) and reflected by the reflecting device (30) towards the respective optical sensor (41), The optical navigation system (100) of any one of claims 1 to 7, wherein the control unit (43) is configured to determine the position of the robot reference (11) within the reference frame of the localization device (40) based on the measurements thus performed by the optical sensor (41).

9. 9. The optical navigation system (100) of claim 8, further comprising a medical robot (10) having an articulated arm (13), the robot fiducial (11) being positioned at a distal end of the articulated arm (13), the medical robot (10) further comprising an articulated encoder of the articulated arm (13) enabling the position of the robot fiducial (11) to be determined at any instant in a reference frame of the localization device (40), the medical robot (10) being configured to transmit the position of the robot fiducial (11) in the reference frame of the localization device (40) to the control unit (43), and the control unit (43) being configured to estimate from the position of the robot fiducial (11) a position of a medical instrument attached to the distal end of the articulated arm (13) of the medical robot (10) relative to the target anatomical structure of the patient (20).

10. The optical navigation system (100) of claim 8 or 9, wherein the optical markers (26, 16) of the patient fiducial (21) and / or the robot fiducial (11) are active markers, and the optical radiation coming from the optical markers (26, 16) is infrared radiation generated by the optical markers (26, 16).

11. 10. The optical navigation system (100) of claim 8 or 9, wherein the optical markers (26, 16) of the patient fiducial (21) and / or the robot fiducial (11) are passive markers and the optical radiation coming from the optical markers (26, 16) is infrared radiation generated by the localization device (40) and reflected by the optical markers (26, 16).

12. A method (200) for determining a position of an anatomical structure of interest in a patient (20), comprising: A location device (40) having at least two optical sensors (41), and A patient fiducial (21) having at least three optical markers (26), the positions of each of the optical markers (26) relative to one another being known a priori, the patient fiducial (21) being positioned on the patient (20) to the anatomical structure of interest. A method (200) implemented by an optical navigation system (100) comprising: The optical navigation system (100) further comprises a reflecting device (30), the position of which within a reference frame of the localization device (40) is known; and The method (200) comprises: if it is determined based on the angle of arrival at each optical sensor (41) of the optical radiation coming from the optical marker (26), that a direct line of sight between the patient fiducial (21) and the respective optical sensor (41) is available, measuring (201) for each optical marker (26) of the patient fiducial (21) a parameter representative of a position of the optical marker (26) within the reference frame of the localization device (40) based on the optical radiation coming from the optical marker (26) and having, for each optical sensor (41), a direct path (22) between the optical marker (26) and the optical sensor (41); if it is determined based on the angle of arrival of the optical radiation at each optical sensor (41) coming from the optical marker (26) that a direct line of sight between the patient fiducial (21) and the optical sensor (41) is interrupted by an obstacle (60), measuring (202) for each optical marker (26) of the patient fiducial (20) a parameter representative of the position of the optical marker (26) within the reference frame of the localization device (40) based on the optical radiation coming from the optical marker (26) and having a path (23) reflected by the reflecting device (30) towards the respective optical sensor (41); determining (203) a position of the patient fiducial (21) in the frame of reference of the localization device (40) based on the measurements thus performed by the optical sensor (41); determining (204) a position of the target anatomical structure based on the position of the patient fiducials (21) within the frame of reference of the localization device (40); The method according to claim 1, further comprising:

13. estimating (205) the movement (24) followed by said patient fiducials (21) in the reference frame of said localization device (40) during a respiratory cycle of said patient (20) during the period when a direct line of sight between said patient fiducials (21) and the respective optical sensor (41) is available, determining (203) the position of the patient fiducial (21) as a function of the measurements performed by the optical sensor (41) on the one hand based on the optical radiation coming from the optical markers (26) of the patient fiducial (21) and reflected by the reflecting device (30), and on the other hand as a function of the estimated movement (24) of the patient fiducial (21), at a time when a direct line of sight between the patient fiducial (21) and the optical sensor (41) is no longer available. The method (200) of claim 12, further comprising:

14. The method (200) according to claim 13, wherein the determination (204) of the position of the target anatomical structure within the reference frame of the localization device (40) is further performed based on a medical image of the target anatomical structure of the patient (20) in which a radiopaque marker (27) of the patient reference (21) is visible.

15. The method (200) of claim 14, wherein the determination (204) of the position of the target anatomical structure within the reference frame of the localization device (40) is further performed based on a biomechanical model of the target anatomical structure, the biomechanical model being configured to model deformations of the anatomical structures and mechanical interactions between the anatomical structures.

16. The optical navigation system (100) further comprises a robotic fiducial (11) intended to be positioned at the distal end of an articulated arm (13) of a medical robot (10), the robotic fiducial (11) comprising at least three optical markers (16), the respective positions of the optical markers (16) relative to one another being known a priori; The method (200) comprises: if it is determined based on the angle of arrival of the optical radiation at each optical sensor (41) coming from the optical marker (26) that a direct line of sight between the robot fiducial (11) and the respective optical sensor (41) is available, measuring, for each optical marker of the robot fiducial (11), a parameter representative of the position of the optical marker (16) within the reference frame of the localization device (40) based on the optical radiation coming from the optical marker (16) and having, for each optical sensor (41), a direct path between the optical marker (16) and the optical sensor (41); if it is determined based on the angle of arrival of the optical radiation at each optical sensor (41) coming from the optical marker (26) that a direct line of sight between the robot reference (11) and the optical sensor (41) is interrupted by an obstacle, measuring, for each optical marker (16) of the robot reference (11), a parameter representative of the position of the optical marker (16) within the reference frame of the localization device (40) based on the optical radiation coming from the optical marker (16) and having a path reflected by the reflecting device (30) towards the respective optical sensor (41); determining the position of the robot reference (11) in the reference frame of the localization device (40) based on the measurements thus performed by the optical sensor (41); The method (200) of any one of claims 12 to 15, further comprising:

17. 17. The method according to claim 16, wherein the optical navigation system further comprises a medical robot having an articulated arm, the robot fiducial being positioned at a distal end of the articulated arm, the medical robot further comprising an articulated encoder of the articulated arm that enables determining at any instant the position of the robot fiducial within a reference frame of the localization device, the method further comprising determining the position of a medical instrument attached to the distal end of the articulated arm of the medical robot relative to the target anatomical structure of the patient.

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