Monitoring device for navigation-guided medical interventions

Abstract

The invention relates to an optical monitoring device (10) for monitoring the movements of an anatomical part of interest of a patient (50) during a minimally invasive medical intervention. The optical monitoring device (10) comprises a base layer (11) that serves as a sterile drape and comprises an intervention region (12) and a marking region (13) which at least partially surrounds the intervention region (12). The marking region (13) comprises, on the inner face, an adhesive material for attaching the monitoring device (10) to the skin of the patient (50) and, on the outer face (11b), at least three optical markers (14) or at least three attachment supports each intended to accommodate an optical marker (14). The marking region (13) also comprises an optical fibre sensor (15) which is securely attached to the base layer (11) and which has a measurement point associated with each of the optical markers (14) or attachment supports.

Description

[0001] Tracking device for navigation-guided medical interventions

[0002] Field of invention

[0003] The devices and methods disclosed in the present application belong to the field of optical navigation for tracking movements of an anatomy of interest of a patient during a minimally invasive medical procedure. More particularly, there is provided a patient skin-based optical tracking device and an optical navigation method using such an optical tracking device.

[0004] State of the art

[0005] Minimally invasive medical procedures require the very precise positioning or movement of a medical instrument (e.g., a needle, a catheter, an electrode, an ultrasound generator, a drill bit, etc.) relative to a patient's anatomy of interest (e.g., the liver, a lung, a kidney, a bone, etc.). The practitioner performing this type of procedure may be assisted by a medical robot. In this case, the medical robot positions, holds, and / or guides a medical instrument relative to the anatomy of interest using a navigation system. The instrument is, for example, attached to one end of an articulated arm of the robot. The navigation system determines the position of the instrument and the position of the anatomy of interest.Information about the respective positions of the instrument and the anatomy of interest relative to each other allows the robot to configure its articulated arm so that the instrument is optimally positioned relative to the anatomy of interest.

[0006] In the case of an optical navigation system, an optical tracking device is typically placed on the patient's skin near the anatomy of interest. This tracking device typically includes at least three optical markers to enable the navigation system to accurately determine the position of the tracking device. The position of the anatomy of interest can then be determined from the position of the tracking device and using a medical image in which both the anatomy of interest and the tracking device (or at least part of the tracking device) are visible.

[0007] During the procedure, the anatomy of interest may be in motion, for example due to the patient's breathing movements. Therefore, it is appropriate to be able to track the position of the anatomy of interest over time using the navigation system. However, the line of sight between an optical marker of the tracking device and an optical sensor of the navigation system may be cut off by an obstacle (for example, by the practitioner, by the instrument, or by the robot's articulated arm), and this may hinder the determination of the position of the tracking device.

[0008] The individual optical markers are sometimes glued individually to the patient's skin. In addition to the fact that this is a relatively long and complex process, the adhesion of the optical markers to the patient's skin is sometimes insufficient and they can be inadvertently peeled off by the practitioner during the procedure. In some cases, the optical markers are all attached to a single adhesive strip intended to be glued to the patient's skin to surround the intervention area. In all cases, the optical markers must not be obscured by the sterile field covering the patient. It is therefore necessary to cut a large opening or several openings at different locations in the sterile field, which is not desirable because it is necessary to disinfect the patient's skin at these opening areas.

[0009] US patent application 2020 / 0008897 A1 describes a tracking device comprising a base layer serving as a sterile field, several optical markers attached to the outer face of the base layer, and an adhesive material on the inner face for bonding the base layer to the patient's skin. During the procedure, an incision is made on the patient through the base layer of the tracking device (i.e., the base layer and the patient's skin must be incised simultaneously because the entire surface of the base layer is adhesive). However, this type of device is not suitable for percutaneous procedures. Indeed, for a percutaneous procedure, the principle is to insert needles directly through the patient's skin, without a prior incision, in order to reduce the risk of patient contamination.It is also common in this type of intervention to treat multiple lesions, or to treat a lesion using multiple needles via different pathways. Thus, simultaneous incision of the tracking device and the patient is not feasible in this minimally invasive practice.

[0010] Statement of the invention

[0011] The solutions proposed in the present application aim to remedy all or part of the drawbacks of the prior art, in particular those set out above.

[0012] To this end, and according to a first aspect, an optical tracking device is proposed for tracking the movements of an anatomy of interest of a patient during a minimally invasive medical procedure. The optical tracking device comprises a base layer serving as a sterile field and having an inner face intended to be oriented towards the patient's skin and an outer face opposite the inner face. The base layer comprises an intervention region corresponding to an opening or a region intended to be cut to reveal an area of ​​the patient's skin where the procedure is to take place. The base layer also comprises a marking region which at least partially surrounds the intervention region. The marking region comprises on the inner face, an adhesive material for fixing the optical tracking device to the patient's skin.The marking region comprises on the outer face, at least three optical markers or at least three fixing supports intended to each receive an optical marker. The marking region also comprises a fiber optic sensor secured to the base layer and having at least one measuring point associated with each of the optical markers or fixing supports.

[0013] The optical tracking device is particularly easy to install on the patient since all the optical markers or all the mounting brackets for the optical markers are integral with each other. Simply apply the adhesive material to the patient's skin to install the optical tracking device.

[0014] The optical tracking device has a minimal footprint in the intervention area. The extended configuration of the tracking device with a punctual distribution of optical markers allows the practitioner to have clear access to the intervention area.

[0015] The configuration of the tracking device allows for optimized adhesion to the patient's skin, thereby limiting the risk of inadvertent displacement of an optical marker during the procedure. The adhesion surface of the adhesive material can be optimized thanks to a priori knowledge of the location of the optical markers on the tracking device.

[0016] The tracking device also reduces the surface area to be disinfected on the patient's skin. Indeed, the tracking device integrates both the sterile field and the optical markers (or the mounting brackets for the optical markers) and the surface to be disinfected corresponds only to the opening of the sterile field corresponding to the intervention region.

[0017] The fiber optic sensor makes it possible to obtain information on the relative position in space of the optical markers with respect to each other. Thus, even if certain optical markers are not visible to the location device (for example if the line of sight between the location device and an optical marker is cut by an obstacle), it remains possible to estimate the position of the optical markers which are not visible from the position of at least one visible optical marker and the relative positions of the optical markers with respect to each other. The fiber optic sensor may in particular comprise an optical fiber with Bragg gratings.

[0018] In particular embodiments, the optical tracking device may further comprise one or more of the following features, taken individually or in any technically possible combination.

[0019] In particular embodiments, the base layer is a polyethylene sheet backed with an absorbent cellulose sheet.

[0020] In particular embodiments, the intervention region is pre-cut in the base layer.

[0021] In particular embodiments, the base layer includes visual indicia delineating the marking region.

[0022] In particular embodiments, the adhesive material takes the form of an adhesive strip connecting together the different points where the optical markers or the fixing supports are located. The adhesive strip provides a semi-rigid connection between the optical markers, which facilitates their installation and optimizes their stability.

[0023] In particular embodiments, the adhesive tape is a polyethylene film coated with an acrylic adhesive or a rayon fabric coated with an acrylic adhesive.

[0024] In particular embodiments, the tracking device further comprises at least three radiopaque markers each rigidly attached respectively to an optical marker or to a fixing support. The radiopaque markers are intended to locate the position of the optical tracking device in a medical image.

[0025] In particular embodiments, the optical markers are active, each active optical marker being configured to emit a differently modulated infrared signal.

[0026] In particular embodiments, the optical markers are passive, and the tracking device comprises at least four optical markers.

[0027] According to a second aspect, an optical navigation system is proposed comprising:

[0028] - an optical tracking device according to any one of the preceding embodiments, the optical tracking device being equipped with optical markers, - a measuring device configured to cooperate with the fiber optic sensor to determine a relative position of each of the optical markers in a reference frame of the measuring device,

[0029] - a location device configured to cooperate with the optical markers to determine a position of each of the optical markers in a reference frame of the location device.

[0030] In the present application, an optical marker is considered "active" when it is configured to directly emit an optical signal without said signal having been generated by another element. In contrast, an optical marker is considered "passive" when it is configured to reflect an optical signal generated by another element.

[0031] According to a third aspect, a navigation method is proposed using an optical navigation system as presented above. The method comprises the following steps:

[0032] - a determination, using the location device, of the position of at least one optical marker visible to the location device,

[0033] - an identification of said at least one visible optical marker among all the optical markers,

[0034] - a determination, using the measuring device, of the relative positions of all the optical markers in relation to each other,

[0035] - a determination of the position of at least one optical marker which is not visible to the location device from the position of the visible optical marker and the relative positions of the optical markers to each other,

[0036] - an estimate of the position of the optical tracking device from the positions of at least three optical markers.

[0037] In particular embodiments, the optical markers are active, each optical marker is configured to emit a differently modulated infrared signal, and the identification of said at least one visible optical marker is carried out by identifying the modulation of the infrared signal emitted by said optical marker.

[0038] In particular embodiments, the optical markers are passive, the optical marking device comprises at least four passive optical markers, the distances between two optical markers taken two by two all differ by at least one predetermined margin value, and the method further comprises the following steps:

[0039] - a determination, using the location device, of the position of at least three optical markers visible to the location device,

[0040] - an identification of said three optical markers, among the set of optical markers, from the distances between two optical markers determined for at least two different pairs of optical markers formed among said at least three visible optical markers.

[0041] In particular embodiments, the navigation method comprises a prior step of generating, for each optical marker, using the location device and the measuring device, a model representative of a substantially cyclical movement of said optical marker. The identification of said at least one visible optical marker is then carried out by identifying the model corresponding to the movement of said visible optical marker.

[0042] Presentation of figures

[0043] The invention will be better understood by reading the following description, given by way of non-limiting example, and made with reference to figures 1 to 4 which represent:

[0044] [Fig. 1] a schematic representation of the outer face of an exemplary embodiment of an optical tracking device according to the invention,

[0045] [Fig. 2] a schematic representation of the inner face of the optical tracking device shown in Figure 1,

[0046] [Fig. 3] a schematic representation of an exemplary embodiment of an optical navigation system using a tracking device shown in Figures 1 and 2,

[0047] [Fig. 4] A schematic representation of the main steps of an optical navigation method using a navigation system shown in Figure 3.

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

[0049] Detailed description of an embodiment of the invention

[0050] Figures 1 and 2 schematically represent an exemplary embodiment of an optical tracking device 10 according to the invention.

[0051] The optical tracking device 10 is intended to be installed on the skin of a patient, close to an anatomy of interest of the patient on which a minimally invasive medical intervention is to be performed. The anatomy of interest corresponds for example to the liver, a lung, a kidney, a bone, etc. The minimally invasive medical intervention aims for example to biopsy or ablate a lesion in the anatomy of interest (for example a cyst, a tumor, etc.). The ablation of the lesion can be carried out by different methods (radiofrequency, microwave, cryotherapy, laser, electroporation, focused ultrasound, etc.). It is then necessary to position or move very precisely a medical instrument (for example a needle, a catheter, an electrode, an ultrasound generator, a drilling bit, etc.) relative to the anatomy of interest of the patient.As will be detailed later, a localization device can be used to estimate the position of the optical tracking device 10 in real time. A pre-interventional medical image that represents both the patient's anatomy of interest and the optical tracking device 10 can make it possible to determine the position of the anatomy of interest by the ratio of the optical tracking device 10. Real-time knowledge of the position of the optical tracking device 10 can then make it possible to determine in real time the position of the patient's anatomy of interest. The medical instrument can then be guided in real time based on the estimated position of the patient's anatomy of interest. It should be noted that the position of the anatomy of interest and the position of the tracking device 10 change over time, in particular due to the patient's respiratory movements.

[0052] In the present application, the expression "the position of the tracking device 10" must be understood in the broad sense, that is to say that it encompasses both the position and the orientation of the tracking device 10 (the term "pose" is sometimes used in English literature to represent the combination of the position and the orientation of an object). The same applies to the expression "the position of the medical instrument" which must be understood as "the position and the orientation of the medical instrument", and to the expression "the position of the anatomy of interest" which must be understood as "the position and the orientation of the anatomy of interest".

[0053] As illustrated in Figures 1 and 2, the optical tracking device 10 comprises a base layer 11 which serves as a sterile field. This base layer 11 has an inner face 11a and an outer face 11b. The inner face 11a is shown in Figure 2. The inner face 11a is intended to be oriented towards the patient's skin. The outer face 11b is shown in Figure 1. The outer face 11b is opposite the inner face 11a.

[0054] The base layer 11 corresponds to a sterile sheet. The base layer 11 comprises, for example, a polyethylene sheet lined with an absorbent cellulose sheet. The inner face 11a of the base layer 11 is then formed by the absorbent cellulose sheet. The polyethylene sheet, which forms the outer face 11b of the base layer, is preferably impermeable to bacteria and liquids to reduce the risk of infection and cross-contamination.

[0055] The base layer 11 includes an intervention region 12 which corresponds to an opening or a region intended to be cut out to reveal an area of ​​the patient's skin where the intervention is to take place. In Figures 1 and 2, the intervention region 12 corresponds to the region located inside the smaller dotted rectangle.

[0056] In particular embodiments, the intervention region 12 corresponds to a pre-cut area in the base layer 11. The portion of the sterile field forming the intervention region 12 can then be easily removed by the practitioner after installation of the optical tracking device 10 on the patient. Alternatively, the intervention region 12 can be cut by the practitioner without being pre-cut. The size and shape of the intervention region 12 are adapted to the intended medical intervention. The intervention region 12 can be located in the center of the base layer 11 or at another location on the base layer 11.

[0057] The base layer 11 also comprises a marking region 13 which at least partially surrounds the intervention region 12. In Figures 1 and 2, the marking region 13 corresponds to the region located between the two dotted rectangles. For example, and as illustrated in Figures 1 and 2, the marking region 13 may take the form of a substantially rectangular band around the intervention region. The marking region 13 could, however, also take another form, such as the form of a substantially circular band, or the form of an arcuate band, or a C-shaped, U-shaped, or V-shaped band which partially surrounds the intervention region 12.

[0058] As illustrated in Figure 2, the marking region 13 has on the inner face 11 an adhesive material 16 for fixing the optical tracking device 10 to the patient's skin.

[0059] As illustrated in FIG. 1, the marking region 13 comprises on the outer face 11b at least three optical markers 14 or at least three fixing supports intended to each accommodate an optical marker 14.

[0060] An optical marker 14 corresponds, for example, to a reflective sphere visible to an infrared stereoscopic camera (as, for example, in the Polaris® navigation solution from Northern Digital Inc.) or black and white patterns visible to a stereoscopic camera (as, for example, in the MicronTracker® navigation solution from ClaroNav). In these examples, the optical markers are passive markers.

[0061] Alternatively, the optical markers may be active markers configured to emit infrared signals detectable by an infrared camera. The optical markers may include retroreflective lenses (such as the Radix® lenses developed by Northern Digital Inc.).

[0062] When the optical markers 14 are active, it is advantageous for each optical marker 14 to be configured to emit a differently modulated infrared signal. It is thus possible to identify each optical marker 14 among all the optical markers 14 from the infrared signal emitted by said optical marker 14.

[0063] It is advantageous to use small optical markers to limit the size of the optical tracking device 10 and facilitate access to the intervention area.

[0064] The optical markers 14 are either directly integrated into the base layer 11 (they can for example be heat-sealed onto the base layer 11), or mounted by an operator on the fixing supports of the optical tracking device 10.

[0065] The position of the optical tracking device 10 is determined from the position of at least three optical markers 14. The optical tracking device 10 may advantageously comprise a number of optical markers 14 (or a number of fixing supports for the optical markers 14) greater than three. This makes it possible to increase the chances of having at least three optical markers 14 visible at a given time even if certain optical markers are hidden by an obstacle.

[0066] The marking region 13 also comprises a fiber optic sensor 15 secured to the base layer 11. As will be detailed later, the fiber optic sensor 15 is intended to be connected to a measuring device to determine the relative position in space of the optical markers 14 with respect to each other. For this purpose, the fiber optic sensor 15 has at least one measuring point associated with each of the optical markers 14 or the fixing supports. The fiber optic sensor can be formed by a Bragg grating fiber, as for example in the solution proposed by the company Sensuron® or by the company The Shape Sensing Company®. The fiber optic sensor 15 can be positioned both on the inner face 11a and on the outer face 11b of the base layer 11.

[0067] A Bragg grating is a resonant microstructure inscribed on the core of an optical fiber. This resonant structure acts as a wavelength-selective mirror (a narrowband filter around a specific wavelength of the Bragg grating): when light travels through the optical fiber, only a narrow part of the light spectrum centered on the Bragg grating wavelength is reflected. The rest of the light spectrum continues along the optical fiber to the next Bragg grating. The wavelength of a Bragg grating is essentially defined by the period of the microstructure and the refractive index of the fiber core. The fiber can contain different Bragg gratings in series, with each Bragg grating associated with a specific wavelength. An optoelectronic measurement device can measure the wavelength reflected by each Bragg grating.Each Bragg grating corresponds to a measurement point. A deformation of the optical fiber causes a change in the period of the microstructure and consequently also a change in the wavelength of the Bragg grating. It is thus possible to determine a deformation applied to the optical fiber at each Bragg grating by measuring a difference between a reference wavelength of the Bragg grating (wavelength of the Bragg grating without deformation) and a measured wavelength of the Bragg grating (wavelength of the Bragg grating with deformation). Measurements of the different deformations applied respectively at the different Bragg gratings make it possible to determine their relative position in space with respect to each other.

[0068] The marking region 13 incorporates various technical elements. This is a technical area that must not be damaged. In particular embodiments, the base layer 11 includes visual indications that delimit the marking region 13. This makes it possible to indicate to the practitioner an area of ​​the sterile field that must not be cut.

[0069] The adhesive material 16 makes it possible to stick the optical tracking device 10 to the patient's skin. This adhesive material can be distributed more or less uniformly, and continuously or not, on the part of the inner face 11a corresponding to the marking region 13.

[0070] In the example considered and illustrated in Figure 2, the adhesive material 16 takes the form of an adhesive strip connecting together the different points where the optical markers 14 or the fixing supports are located.

[0071] The adhesive strip is, for example, a polyethylene film coated with an acrylic adhesive or a rayon fabric coated with an acrylic adhesive. The use of a rayon fabric allows the base layer 11 to retain its absorbent character in contact with the patient.

[0072] The adhesive strip may be attached to the base layer 11 by sewing or gluing. The adhesive strip provides a semi-rigid bond between the optical markers, facilitating their installation and optimizing their stability. The strip shape also minimizes the footprint of the marking region 13.

[0073] As mentioned previously, a pre-interventional medical image may represent both the patient's anatomy of interest and the optical tracking device 10 to enable the position of the anatomy of interest to be determined relative to the optical tracking device 10.

[0074] This could be, for example, a medical image obtained by computed tomography (or “CT-scan”), angiography, or magnetic resonance imaging (MRI).

[0075] In particular embodiments, the optical tracking device 10 comprises at least three radiopaque markers each rigidly attached respectively to an optical marker 14 or to a fixing support, to help determine the position of the optical tracking device 10 on the medical image. These radiopaque markers may be, for example, ceramic beads or adhesives comprising a radiopaque ink.

[0076] It should be noted, however, that these radiopaque markers are not necessarily essential because the nature of the materials used to manufacture certain elements of the optical tracking device 10 (in particular the optical markers 14) can sometimes make it possible to visualize these elements on the medical image.

[0077] Figure 3 schematically represents an exemplary embodiment of an optical navigation system 20 according to the invention.

[0078] The optical navigation system 20 comprises an optical tracking device 10 according to any one of the embodiments previously described. The optical tracking device 10 is equipped with optical markers 14. In the example illustrated in FIG. 3, the optical tracking device 10 corresponds to that previously described with reference to FIGS. 1 and 2.

[0079] The optical navigation system 20 also comprises a location device 40 configured to cooperate with the optical markers 14 to determine the position of the optical markers 14 in a frame of reference of the location device 40.

[0080] The location device 40 comprises, for example, a stereoscopic camera operating in the infrared radiation range or in the visible light range. The stereoscopic camera comprises two optical sensors 41 configured to receive light signals from the optical markers 14 and to deduce therefrom the position of the optical markers 14 (from a time and / or an angle of arrival of each light signal). These may be light signals directly transmitted by the optical markers 14 when the optical markers 14 are active, or light signals reflected by the optical markers 14 when the optical markers 14 are passive. A ToF (Time of Flight) or RGB-D (Red Green Blue - Depth) type camera may be used when the optical markers 14 are active. As a non-limiting example, the Polaris® navigation solution proposed by the company Northern Digital Inc.uses a stereoscopic infrared camera.

[0081] The location device 40 may further comprise an additional camera 42 for continuously acquiring images of the procedure. The camera 42 may in particular be integrated into the stereoscopic camera system to have the same field of vision axis. The camera 42 may for example be used to track the insertion of the medical instrument and to estimate the insertion depth of the medical instrument at a given time.

[0082] In the example considered and illustrated in Figure 3, a patient 50 is positioned on an intervention table 70 to undergo a minimally invasive medical intervention on an anatomy of interest. The optical tracking device 10 is positioned on the skin of the patient 50 near the anatomy of interest. A medical robot 60 is used to assist the practitioner during the intervention. The medical robot comprises, for example, an articulated arm at the end of which a medical instrument is attached.

[0083] The purpose of the location device 40 is to determine in real time the position of the optical markers 14 in order to deduce therefrom the position of the optical tracking device 10 in order to ultimately determine the position of the anatomy of interest. The location device 40 may also be configured to determine the position of the medical instrument using another optical tracking device positioned on the medical robot 60 or directly on the medical instrument. The position of the medical instrument may also be determined using the camera 42. When the respective positions of the medical instrument and the anatomy of interest relative to each other are known (for example in a reference frame of the location device 40), it is possible to configure the articulated arm of the medical robot 60 to position the medical instrument optimally relative to the anatomy of interest.

[0084] The localization device 40 comprises, for example, a control unit comprising one or more processors configured to determine the respective positions of the anatomy of interest and of the medical instrument relative to each other, as well as a communication module configured to transmit this information to the medical robot 60.

[0085] The optical navigation system 20 also comprises a measuring device 30 configured to cooperate with the fiber optic sensor 15 to determine the relative position of each of the optical markers 14 in a frame of reference of the measuring device 30. The fiber optic sensor 15 is for example connected to the measuring device 30 once the optical tracking device 10 is positioned on the patient 50.

[0086] The measuring device 30 and the fiber optic sensor 15 form a redundant device with respect to the locating device 40 for determining the position of the optical markers 14. This is particularly useful when one or more of the optical markers 14 are not visible to the locating device 40. This is the case, for example, when the line of sight between an optical sensor 41 and an optical marker 14 is interrupted by an obstacle (for example, the practitioner, an operator, the articulated arm of the medical robot 60, the medical instrument, etc.). When an optical marker 14 is not visible, the locating device 40 cannot determine its position. However, if at least one optical marker 14 is visible and can be identified among all the optical markers, and if the relative position of each of the optical markers 14 with respect to each other is known, then it is possible to deduce the position of all the optical markers 14.

[0087] It is thus possible to supplement the information obtained by the location device 40 with the information provided by the measurement device 30. This makes it possible to optimize the precision of the location device 40 because all of the optical markers 14 can be used permanently.

[0088] Figure 4 schematically describes the main steps of an optical navigation method 100 using a navigation system 20 as described above with reference to Figure 3.

[0089] The method 100 comprises a step 101 of determining, using the location device 40, the position of at least one optical marker 14 visible to the location device 40 (this means that the line of sight between the optical marker 14 and the location device 40 is not interrupted by an obstacle).

[0090] The method 100 then comprises a step 102 of identifying said visible optical marker 14 among the set of optical markers 14. As will be detailed later, there are different ways of identifying an optical marker 14 among the set of optical markers 14.

[0091] The method 100 comprises a step 103 of determining, using the measuring device 30, the relative positions of all the optical markers 14 with respect to each other.

[0092] The method 100 comprises a step 104 of determining the position of at least one optical marker 14 which is not visible to the location device 40 from the position of the visible optical marker 14 and the relative positions of the optical markers 14 with respect to each other.

[0093] Finally, the method 100 comprises a step 105 of estimating the position of the optical tracking device 10 from the positions of at least three optical markers 14.

[0094] There may be different ways to identify an optical marker 14 among the set of optical markers 14.

[0095] According to a first example, if the optical markers 14 are active, each optical marker 14 can be configured to emit a differently modulated infrared signal. The identification 102 of a visible optical marker 14 can then be carried out by identifying the modulation of the infrared signal emitted by said optical marker 14.

[0096] According to a second example, for passive optical markers 14, it is possible to envisage placing at least four optical markers 14 on the optical tracking device 10 in a particular way making it possible to identify optical markers unambiguously as soon as at least three optical markers are visible. The optical markers 14 can for example be positioned such that the distances separating two optical markers 14 taken two by two all differ by at least a predetermined margin value (for example, whatever the optical markers considered, the distance between two optical markers must differ by at least 5 mm compared to the distance separating two other optical markers).When the positions of at least three visible optical markers 14 are determined by the location device 40, it is then possible to unambiguously identify said three optical markers 14 from among all the optical markers 14, from the distances between two optical markers 14 determined for at least two different pairs of optical markers 14 formed from among said at least three visible optical markers 14.

[0097] According to a third example, the method 100 may comprise a prior step of generating, for each optical marker 14, using the location device 40 and the measurement device 30, a model representative of a substantially cyclical movement of said optical marker 14. In this case, it is possible to identify a visible optical marker 14 by identifying the model corresponding to the observed movement of said visible optical marker 14.

[0098] In other words, in this third example, the identification 102 of a visible optical marker 14 is carried out by jointly using the movement information provided by the measuring device 30 and that provided by the optical location device 40. The identification 102 of a visible optical marker 14 is determined by analyzing the movement characteristics of each of the optical markers 14, matching the information provided by the measuring device 30 and that provided by the optical location device 40, and using these movement characteristics to unambiguously identify the visible optical marker.Under the assumption of a substantially cyclical movement, as is the case for the movement generated by the breathing of the patient 50, this matching method can make it possible to reconstruct the complete location information of the optical tracking device 10 even if only one of the optical markers 14 is visible. The movement characteristics of an optical marker 14 can for example correspond to an amplitude of the movement of the optical marker 14 and / or to a frequency of movement of the optical marker 14 in a main direction followed by the optical marker 14. These characteristics form a model representative of the movement of the optical marker 14 during a cycle.

[0099] The optical navigation method 100 makes it possible to significantly limit the problems of loss of line of sight while maintaining good precision thanks to the joint use of, on the one hand, the precise absolute location information in space provided by the location device 40, and on the other hand, the relative position information provided by the measurement device 30.

[0100] In the example illustrated in Figure 3, the optical navigation system 20 can be used in the following manner.

[0101] The patient 50 is put into apnea, or the practitioner asks the patient 50 to hold his breath, and the position of the optical markers 14 is recorded (when the patient is in apnea, the position of the optical markers 14 is fixed).

[0102] A pre-interventional medical image of the patient 50 is acquired while the patient 50 is holding his breath. The pre-interventional medical image makes it possible to visualize both the anatomy of interest of the patient 50 and the optical tracking device 10. This makes it possible to determine the position of the anatomy of interest by the optical tracking device 10 ratio at the instant in the respiratory cycle when the patient is holding his breath. Knowing the position of the optical tracking device 10 at this instant can then make it possible to determine in real time the position of the patient's anatomy of interest at this instant. The patient's breathing then resumes normally.

[0103] The pre-interventional medical image is used to plan the surgical procedure. For example, it is possible to determine a trajectory that the medical instrument must follow during its insertion. The trajectory is, for example, defined from an entry point at the patient's skin and a target point at the lesion to be treated. In order to insert a medical needle, the patient is put back into apnea at a time when the position of the optical tracking device 10 is substantially at the same position as when the pre-interventional medical image was acquired (i.e., substantially at the same phase of the respiratory cycle). This ensures that the anatomy of interest is substantially at the same position as that represented on the pre-interventional medical image used to plan the procedure.

[0104] During these operations, the practitioner may possibly obstruct the line of sight of one or more optical markers 14 of the optical tracking device 10. As soon as at least one optical marker 14 that can be identified among all the optical markers 14 is visible by the location device 40, the position of the optical tracking device 10 can be determined with good precision thanks to the redundancy provided by the optical fiber sensor 15 and the measuring device 30. The optical navigation system 20 can also make it possible to detect an unexpected movement of the patient.

[0105] In some cases, it is necessary to insert multiple medical instruments (or to insert the same medical instrument multiple times) to reach different target points at the lesion. The configuration of the tracking device 10 allows this without particular constraint on the entry point.

[0106] The above description clearly illustrates that, through its various characteristics and their advantages, the various devices and methods presented achieve the set objectives. In particular, the optical tracking device 10 is easy to install, it has a minimal footprint in the intervention area, it makes it possible to optimize adhesion to the skin of the patient 50, it makes it possible to limit the surface to be disinfected on the skin of the patient 50, and it guarantees good navigation precision even if certain optical markers 14 are not visible by the location device 40.

[0107] It should be noted that the implementation and embodiment methods considered above have been described as non-limiting examples, and that other variants are consequently conceivable.

[0108] In particular, the choice of a particular dimension, shape or composition of the base layer 11 of the tracking device 10 is only a variant of the invention. The same applies to the choice of a particular shape of the marking region 13, or a particular position of the marking region 13 on the base layer 11. The same also applies to the choice of a particular dimension, shape or position of the intervention region 12 on the base layer 11.

[0109] As explained above, the optical markers 14 of the tracking device 10 can be either active markers or passive markers. For the optical navigation method 100, different methods have been presented for identifying at least one visible optical marker 14 among all the optical markers 14 of the tracking device 10. Other methods could however be used in this method 100, and the choice of a particular method is only a variant of the invention.

Claims

Claims Optical tracking device (10) for tracking movements of an anatomy of interest of a patient (50) during a minimally invasive medical procedure, said optical tracking device (10) comprising a base layer (11) serving as a sterile field and having an inner face (11a) intended to be oriented towards the skin of the patient (50) and an outer face (11b) opposite the inner face (11a), said base layer (11) comprising an intervention region (12) corresponding to an opening or a region intended to be cut to reveal an area of ​​the skin of the patient (50) where the procedure is to take place, and a marking region (13) which at least partially surrounds the intervention region (12), said marking region (13) comprising: - on the inner face (1 1 a), an adhesive material (16) for fixing the optical tracking device (10) to the skin of the patient (50), - on the outer face (11 b), at least three optical markers (14) or at least three fixing supports intended to each accommodate an optical marker (14), - a fiber optic sensor (15) secured to the base layer (11) and having at least one measuring point associated with each of the optical markers (14) or fixing supports, the fiber optic sensor (15) comprising a Bragg grating optical fiber. Optical tracking device (10) according to claim 1 wherein the base layer (11) is a polyethylene sheet lined with an absorbent cellulose sheet. Optical tracking device (10) according to any one of claims 1 to 2 wherein the intervention region (12) is pre-cut in the base layer. Optical tracking device (10) according to any one of claims 1 to 3 wherein the base layer (11) comprises visual indications delimiting the marking region (13). Optical tracking device (10) according to any one of claims 1 to 4 wherein the adhesive material (16) takes the form of an adhesive strip connecting between them the different points where the optical markers (14) or the fixing supports are located.

6. An optical tracking device (10) according to claim 5 wherein the adhesive strip is a polyethylene film coated with an acrylic adhesive or a rayon fabric coated with an acrylic adhesive.

7. Optical tracking device (10) according to any one of claims 1 to 6 comprising at least three radiopaque markers each rigidly linked respectively to an optical marker (14) or to a fixing support.

8. Optical tracking device (10) according to any one of claims 1 to 7 wherein the optical markers (14) are active, each active optical marker (14) being configured to emit a differently modulated infrared signal.

9. Optical tracking device (10) according to any one of claims 1 to 7 in which the optical markers (14) are passive, and comprising at least four optical markers (14).

10. Optical navigation system (20) comprising: - an optical tracking device (10) according to any one of claims 1 to 7, said optical tracking device (10) being equipped with optical markers (14), - a measuring device (30) configured to cooperate with the fiber optic sensor (15) to determine a relative position of each of the optical markers (14) in a frame of reference of the measuring device (30), - a location device (40) configured to cooperate with the optical markers (14) to determine a position of each of the optical markers (14) in a frame of reference of the location device (40). 1 1. Method (100) of optical navigation using an optical navigation system (20) according to claim 10, said method (100) comprising: - a determination (101), using the location device (40), of the position of at least one optical marker (14) visible to the location device (40), - an identification (102) of said at least one optical marker (14) visible among the set of optical markers (14), - a determination (103), using the measuring device (30), of the relative positions of all the optical markers (14) with respect to each other, - a determination (104) of the position of at least one optical marker (14) which is not visible to the location device (40) from the position of the visible optical marker (14) and the relative positions of the optical markers (14) with respect to each other, - an estimation (105) of the position of the optical tracking device (10) from the positions of at least three optical markers (14). Optical navigation method (100) according to claim 11 wherein the optical markers (14) are active, each optical marker (14) is configured to emit a differently modulated infrared signal, and the identification (102) of said at least one visible optical marker (14) is carried out by identifying the modulation of the infrared signal emitted by said optical marker (14). Optical navigation method (100) according to claim 11 wherein the optical markers (14) are passive, the optical marking device (10) comprises at least four passive optical markers (14), the distances between two optical markers (14) taken two by two all differ by at least one predetermined margin value, and the method (100) comprises: - a determination (101), using the location device (40), of the position of at least three optical markers (14) visible to the location device (40), - an identification (102) of said three optical markers (14), among the set of optical markers (14), from the distances between two optical markers (14) determined for at least two different pairs of optical markers (14) formed among said at least three visible optical markers (14). Optical navigation method (100) according to claim 1 1 comprising a prior step of generating, for each optical marker (14), using the location device (40) and the measurement device (30), a model representative of a substantially cyclical movement of said optical marker (14), and wherein the identification (102) of said at least one visible optical marker (14) is performed by identifying the pattern corresponding to the movement of said visible optical marker (14).

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