Navigation-guided medical intervention tracking device

Abstract

An optical tracking device (10) is proposed for tracking the movements of an anatomy of interest in a patient (50) during a minimally invasive medical procedure. The optical tracking device (10) comprises a base layer (11) serving as a sterile field and including an intervention region (12) and a marking region (13) that at least partially surrounds the intervention region (12). The marking region (13) has, on its inner surface, an adhesive material for fixing the tracking device (10) to the patient's skin (50) and, on its outer surface (11b), at least three optical markers (14) or at least three fixation brackets, each intended to accommodate an optical marker (14). The marking region (13) also includes a fiber optic sensor (15) attached to the base layer (11) and having a measurement point associated with each of the optical markers (14) or fixation brackets. Figure for the abstract: Fig. 3

Description

Title of the invention: Tracking device for navigation-guided medical interventions Scope of the invention

[0001] The devices and methods disclosed in this application fall within the field of optical navigation for tracking the movements of a patient's anatomy of interest during a minimally invasive medical procedure. More specifically, an optical tracking device based on the patient's skin and an optical navigation method using such an optical tracking device are proposed. State of the art

[0002] Minimally invasive medical procedures require the precise positioning or movement of a medical instrument (e.g., a needle, catheter, electrode, ultrasound generator, drill bit, etc.) relative to a patient's anatomy of interest (e.g., the liver, lung, kidney, bone, etc.). The practitioner performing this type of procedure may be assisted by a medical robot. In this case, the medical robot positions, maintains, 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 relative positions of the instrument and the anatomy of interest allows the robot to configure its articulated arm so that the instrument is optimally positioned relative to the anatomy of interest.

[0003] In the case of an optical navigation system, an optical tracking device is generally 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 precisely 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 with the aid of a medical image on which both the anatomy of interest and the tracking device (or at least a portion of the tracking device) are visible.

[0004] During the procedure, the anatomy of interest may be in motion, for example due to the patient's respiratory movements. It is therefore necessary 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 interrupted by an obstacle (e.g., (e.g., by the practitioner, by the instrument or by the articulated arm of the robot), and this can interfere with determining the position of the tracking device.

[0005] The various optical markers are sometimes individually affixed to the patient's skin. Besides 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 detached by the practitioner during the procedure. In some cases, the optical markers are all attached to a single adhesive strip intended to be affixed to the patient's skin to surround the intervention area. In all cases, the optical markers must not be obscured by the sterile drape covering the patient. It is therefore necessary to cut one or more large openings at different locations in the sterile drape, which is undesirable because it is necessary to disinfect the patient's skin at these openings.

[0006] US patent application 2020 / 0008897 A1 describes a tracking device comprising a base layer serving as a sterile field, several optical markers fixed to the outer surface of the base layer, and an adhesive material on the inner surface for attaching the base layer to the patient's skin. During the procedure, an incision is made in the patient through the base layer of the tracking device (in other words, 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 procedure to treat multiple lesions, or to treat a single lesion using multiple needles via different pathways. Therefore, simultaneous incision of the monitoring device and the patient is not feasible with this minimally invasive technique. Description of the invention

[0007] The solutions proposed in this application are intended to remedy all or part of the disadvantages of the prior art, in particular those set out above.

[0008] To this end, and according to a first aspect, an optical tracking device is proposed for monitoring 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 includes an intervention area corresponding to an opening or an area intended to be cut to expose a zone of the skin of the The base layer also includes a marking region that at least partially surrounds the intervention area. The marking region has an adhesive material on its inner surface for attaching the optical tracking device to the patient's skin. The marking region has at least three optical markers or at least three mounting brackets, each designed to accommodate an optical marker, on its outer surface. The marking region also includes a fiber optic sensor attached to the base layer and having at least one measurement point associated with each of the optical markers or mounting brackets.

[0009] The optical tracking device is particularly easy to install on the patient since all the optical markers or all the fixing supports for the optical markers are attached to each other. Simply applying the adhesive material to the patient's skin is enough to install the optical tracking device.

[0010] The optical tracking device has a minimal footprint in the intervention area. The extended configuration of the tracking device with a point distribution of optical markers allows the practitioner to have unobstructed access to the intervention area.

[0011] The configuration of the tracking device optimizes its adhesion to the patient's skin, thereby limiting the risk of unintentional displacement of an optical marker during the procedure. The adhesive surface area of ​​the adhesive material can be optimized by knowing the position of the optical markers on the tracking device in advance.

[0012] The tracking device also makes it possible to reduce the area to be disinfected on the patient's skin. Indeed, the tracking device integrates both the sterile field and the optical markers (or the fixing supports for the optical markers), and the area to be disinfected corresponds only to the opening of the sterile field corresponding to the area of ​​intervention.

[0013] The optical fiber 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 some optical markers are not visible to the localization device (for example, if the line of sight between the localization device and an optical marker is interrupted by an obstacle), it is still possible to estimate the position of the optical markers that 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.

[0014] In particular embodiments, the optical tracking device may further comprise one or more of the following features, taken individually or in all technically possible combinations.

[0015] In particular embodiments, the base layer is a poly- sheet ethylene lined with an absorbent cellulose sheet.

[0016] In particular embodiments, the intervention region is pre-cut in the base layer.

[0017] In particular embodiments, the base layer includes visual indications delimiting the marking region.

[0018] In particular embodiments, the adhesive material takes the form of an adhesive strip connecting the various points where the optical markers or mounting supports are located. The adhesive strip provides a semi-rigid bond between the optical markers, which facilitates their installation and optimizes their stability.

[0019] In particular embodiments, the adhesive strip is a polyethylene film coated with an acrylic adhesive or a rayon fabric covered with an acrylic adhesive.

[0020] In particular embodiments, the tracking device further comprises at least three radiopaque markers, each rigidly attached respectively to an optical marker or a fixation support. The radiopaque markers are intended to locate the position of the optical tracking device in a medical image.

[0021] In particular embodiments, the optical markers are active, each active optical marker being configured to emit a differently modulated infrared signal.

[0022] In particular embodiments, the optical markers are passive, and the tracking device comprises at least four optical markers.

[0023] According to a second aspect, an optical navigation system is proposed comprising: - an optical tracking device according to any of the preceding embodiments, the optical tracking device being equipped with optical markers, - a measuring device configured to cooperate with the optical fiber sensor to determine a relative position of each of the optical markers in a reference frame of the measuring device, - a localization device configured to cooperate with optical markers to determine a position of each of the optical markers in a reference frame of the localization device.

[0024] In the present application, an optical marker is considered "active" when it is configured to directly emit an optical signal without that 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.

[0025] According to a third aspect, a navigation method using a Optical navigation system as described above. The process comprises the following steps: - a determination, using the localization device, of the position of at least one optical marker visible to the localization device, - identification of said at least one visible optical marker among all optical markers, - a determination, using the measuring device, of the relative positions of all the optical markers with respect to each other, - a determination of the position of at least one optical marker that is not visible to the localization device, based on the position of the visible optical marker and the relative positions of the optical markers with respect to each other, - an estimation of the position of the optical tracking device from the positions of at least three optical markers.

[0026] 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.

[0027] In particular embodiments, the optical markers are passive, the optical marking device comprises at least four passive optical markers, the distances between any two pairs of optical markers all differ by at least a predetermined margin value, and the method further comprises the following steps: - a determination, using the localization device, of the position of at least three optical markers visible to the localization device, - 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.

[0028] In particular embodiments, the navigation method includes a preliminary step of generating, for each optical marker, using the localization device and the measuring device, a model representative of a substantially cyclic 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. Presentation of the figures

[0029] The invention will be better understood upon reading the following description, given by way of non-limiting example, and made with reference to Figures 1 to 4, which represent:

[0030] [Fig. 1] a schematic representation of the outer face of an example embodiment of an optical tracking device according to the invention,

[0031] [Fig.2] a schematic representation of the inner face of the tracking device optics represented in [Fig.1],

[0032] [Fig.3] a schematic representation of an example embodiment of a system of optical navigation using a tracking device shown in Figures 1 and 2,

[0033] [Fig.4] a schematic representation of the main steps of a na process optical surveillance using a navigation system shown in [Fig.3].

[0034] In these figures, identical reference numerals from one figure to another designate identical or analogous elements. For clarity, the elements shown are not necessarily to the same scale, unless otherwise stated.

[0035] Detailed description of an embodiment of the invention

[0036] Figures 1 and 2 schematically represent an example of an embodiment of an optical tracking device 10 according to the invention.

[0037] The optical tracking device 10 is intended to be installed on the skin of a patient, near an anatomy of interest of the patient on which a minimally invasive medical intervention is to be performed.

[0038] 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 (e.g., a cyst, a tumor, etc.). Ablation of the lesion can be performed by various methods (radiofrequency, microwave, cryotherapy, laser, electroporation, focused ultrasound, etc.). It is then necessary to position or move a medical instrument (e.g., a needle, a catheter, an electrode, an ultrasound generator, a drill bit, etc.) very precisely relative to the patient's anatomy of interest. 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-intervention medical image that represents both the patient's anatomy of interest and the optical tracking device 10 can be used to determine the position of the anatomy of interest relative to the optical tracking device 10. Real-time knowledge of the optical tracking device 10's position can then be used to determine the position of the patient's anatomy of interest in real time. 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, particularly due to the patient's respiratory movements.

[0039] In this application, the expression "the position of the tracking device 10" must to be understood in a broad sense, that is to say, it encompasses both the position and orientation of the tracking device 10 (the term "pose" is sometimes used in Anglo-Saxon literature to represent the combination of the position and orientation of an object). The same applies to the expression "the position of the medical instrument," which should be understood as "the position and orientation of the medical instrument," and to the expression "the position of the anatomy of interest," which should be understood as "the position and orientation of the anatomy of interest."

[0040] 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 1la and an outer face 11b. The inner face 1la is shown in [Fig. 2]. The inner face 1la is intended to be oriented towards the patient's skin. The outer face 11b is shown in [Fig. 1]. The outer face 11b is opposite the inner face 1a.

[0041] 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 1la 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.

[0042] The base layer 11 includes an intervention area 12 which corresponds to an opening or region intended to be cut out to expose an area of ​​the patient's skin where the intervention is to take place. In Figures 1 and 2, the intervention area 12 corresponds to the region located inside the smaller dashed rectangle.

[0043] In particular embodiments, the intervention area 12 corresponds to a pre-cut zone in the base layer 11. The portion of the sterile field forming the intervention area 12 can then be easily removed by the practitioner after the optical tracking device 10 has been placed on the patient. Alternatively, the intervention area 12 can be cut out by the practitioner without being pre-cut. The size and shape of the intervention area 12 are adapted to the intended medical procedure. The intervention area 12 can be located in the center of the base layer 11 or at another location within the base layer 11.

[0044] The base layer 11 also includes 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 area between the two dashed rectangles. For example, and as illustrated in Figures 1 and 2, the marking region 13 can take the form of a substantially rectangular band around the intervention region. However, the marking region 13 could also take another form, such as the shape of a substantially circular band, or the shape of a band in an arc of a circle, or a band in the shape of a C, a U, or a V that partially encloses the intervention area 12.

[0045] As illustrated in [Fig.2], the marking region 13 has on the inner face 1 an adhesive material 16 for fixing the optical tracking device 10 to the patient's skin.

[0046] As illustrated in [Fig.1], the marking region 13 has on the outer face 11b at least three optical markers 14 or at least three mounting supports intended to accommodate each one optical marker 14.

[0047] 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 to 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.

[0048] 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, for example, the Radix® lenses developed by Northern Digital Inc.).

[0049] 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. This makes it possible to identify each optical marker 14 among all the optical markers 14 based on the infrared signal emitted by said optical marker 14.

[0050] It is advantageous to use small optical markers to limit the bulk of the optical tracking device 10 and facilitate access to the intervention area.

[0051] 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 mounting supports of the optical tracking device 10.

[0052] 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 include more than three optical markers 14 (or more than three mounting brackets for the optical markers 14). This increases the likelihood of having at least three optical markers 14 visible at any given time, even if some optical markers are obscured by an obstacle.

[0053] The marking region 13 also includes a fiber optic sensor 15 attached to the base layer 11. As will be detailed later, the optical fiber 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 optical fiber sensor 15 has at least one measuring point associated with each of the optical markers 14 or their mounting brackets. The optical fiber sensor can be formed by a Bragg grating fiber, as for example in the solution offered by Sensuron® or The Shape Sensing Company®. The optical fiber sensor 15 can be positioned on either the inner face 1a or the outer face 11b of the base layer 11.

[0054] 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 wavelength specific to the Bragg grating): when light travels along the optical fiber, only a narrow portion of the light spectrum centered on the wavelength of the Bragg grating 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 several Bragg gratings in series, each Bragg grating being associated with a specific wavelength. An optoelectronic measuring 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 the deformation applied to the optical fiber at each Bragg grating by measuring the 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). The measurements of the different deformations applied to the different Bragg gratings allow their relative positions in space to be determined.

[0055] The marking area 13 incorporates various technical elements. It is a technical zone that must not be damaged. In particular embodiments, the base layer 11 includes visual indications that delimit the marking area 13. This allows the practitioner to be shown an area of ​​the sterile field that must not be cut.

[0056] The adhesive material 16 allows the optical tracking device 10 to be attached to the patient's skin. This adhesive material can be distributed more or less uniformly, and continuously or not, over the portion of the inner surface lia corresponding to the region marking 13.

[0057] In the example considered and illustrated in [Fig.2], the adhesive material 16 takes the form of an adhesive strip connecting the different points where the optical markers 14 or the fixing supports are located.

[0058] The adhesive strip is, for example, a polyethylene film coated with an acrylic adhesive or a rayon fabric covered with an acrylic adhesive. The use of a rayon fabric allows the absorbent properties of the base layer 11 in contact with the patient to be maintained.

[0059] The adhesive strip can be attached to the base layer 11 by stitching or gluing. The adhesive strip provides a semi-rigid bond between the optical markers, facilitating their installation and optimizing their stability. The strip's shape also minimizes the footprint of the marking area 13.

[0060] As previously mentioned, a pre-intervention medical image can represent both the patient's anatomy of interest and the optical tracking device 10 to allow the position of the anatomy of interest to be determined by the ratio of the optical tracking device 10.

[0061] This may be, for example, a medical image obtained by computed tomography scan (CT scan), angiography, or magnetic resonance imaging (MRI).

[0062] 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 fixation 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 containing radiopaque ink.

[0063] It should be noted, however, that these radio-opaque 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 allow these elements to be visualized on the medical image.

[0064] Fig. 3 schematically represents an example of an embodiment of an optical navigation system 20 according to the invention.

[0065] The optical navigation system 20 includes an optical tracking device 10 according to any one of the embodiments described above. The optical tracking device 10 is equipped with optical markers 14. In the example shown in [Fig. 3], the optical tracking device 10 corresponds to that described above with reference to Figures 1 and 2.

[0066] The optical navigation system 20 also includes a localization device 40 configured to cooperate with the optical markers 14 to determine the position of the optical markers 14 in a reference frame of the localization device 40.

[0067] The localization device 40 includes, for example, a stereoscopic camera operating in the infrared radiation range or in the visible light range. The stereoscopic camera includes two optical sensors 41 configured to receive light signals from the optical markers 14 and to deduce the position of the optical markers 14 (from a time and / or 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) camera may be used when the optical markers 14 are active.As a non-limiting example, the Polaris® navigation solution offered by Northern Digital Inc. uses a stereoscopic infrared camera.

[0068] The localization device 40 may further include 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 view 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.

[0069] In the example considered and illustrated in [Fig. 3], a patient 50 is positioned on an operating table 70 to undergo a minimally invasive medical procedure on an anatomy of interest. The optical tracking device 10 is positioned on the skin of patient 50 near the anatomy of interest. A medical robot 60 is used to assist the practitioner during the procedure. The medical robot includes, for example, an articulated arm to the end of which a medical instrument is attached.

[0070] The localization device 40 is designed to determine the position of the optical markers 14 in real time, thereby deducing the position of the optical tracking device 10 and ultimately determining the position of the anatomy of interest. The localization device 40 can 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 can 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 localization device 40), it is possible to configure the articulated arm of the medical robot 60 to optimally position the medical instrument relative to the anatomy of interest.

[0071] The location device 40 includes, for example, a control unit comprising one or more processors configured to determine the respective positions of the anatomy of interest and the medical instrument relative to each other, and a communication module configured to transmit this information to the medical robot 60.

[0072] The optical navigation system 20 also includes a measuring device 30 configured to cooperate with the optical fiber sensor 15 to determine the relative position of each of the optical markers 14 in a reference frame of the measuring device 30. The optical fiber sensor 15 is, for example, connected to the measuring device 30 once the optical tracking device 10 is positioned on the patient 50.

[0073] The measuring device 30 and the optical fiber 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 (e.g., 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..

[0074] It is thus possible to supplement the information obtained by the localization device 40 with the information provided by the measurement device 30. This optimizes the accuracy of the localization device 40 because all the optical markers 14 can be used continuously.

[0075] Fig. 4 schematically describes the main steps of an optical navigation method 100 using a navigation system 20 as described above with reference to Fig. 3.

[0076] The method 100 includes a step of determining 101, using the localization device 40, the position of at least one optical marker 14 visible to the localization device 40 (it is meant that the line of sight between the optical marker 14 and the localization device 40 is not interrupted by an obstacle).

[0077] The process 100 then includes an identification step 102 of said visible optical marker 14 among the set of optical markers 14. As will be detailed later, there are different ways to identify an optical marker 14 among the set of optical markers 14.

[0078] The method 100 includes a step 103 of determining, using the measuring device 30, the relative positions of all the optical markers 14 to one another by relationship with others.

[0079] The method 100 includes a step of determining the position of at least one optical marker 14 which is not visible to the localization 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.

[0080] Finally, the method 100 includes a step of estimating 105 the position of the optical tracking device 10 from the positions of at least three optical markers 14.

[0081] There may be different ways to identify an optical marker 14 among the set of optical markers 14.

[0082] 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.

[0083] According to a second example, for passive optical markers 14, it is possible to place at least four optical markers 14 on the optical tracking device 10 in a particular way that allows optical markers to be identified 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 any two optical markers 14, taken two at a time, all differ by at least a predetermined margin value (for example, regardless of the optical markers considered, the distance between two optical markers must differ by at least 5 mm from the distance separating any two other optical markers).When the positions of at least three visible optical markers 14 are determined by the localization 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 said at least three visible optical markers 14.

[0084] According to a third example, the method 100 may include a preliminary step of generating, for each optical marker 14, using the localization device 40 and the measurement device 30, a model representative of a substantially cyclic 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.

[0085] In other words, in this third example, the identification 102 of a visible optical marker 14 is carried out using joint information from The movement information provided by the measuring device 30 and that provided by the optical localization device 40 are used. The identification 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 with that provided by the optical localization device 40, and using these movement characteristics to unambiguously identify the visible optical marker. Assuming a substantially cyclical movement, such as that generated by the patient's breathing, this matching method can reconstruct the complete localization information of the optical tracking device 10 even if only one of the optical markers 14 is visible.The motion characteristics of an optical marker 14 may, for example, correspond to an amplitude of the displacement of the optical marker 14 and / or a frequency of displacement of the optical marker 14 along a principal direction followed by the optical marker 14. These characteristics form a representative model of the motion of the optical marker 14 during a cycle.

[0086] The optical navigation method 100 makes it possible to significantly limit the problems of loss of line of sight while maintaining good accuracy thanks to the joint use on the one hand of the precise information of absolute location in space provided by the location device 40, and on the other hand of the relative position information provided by the measurement device 30.

[0087] In the example illustrated in [Fig.3], the optical navigation system 20 can be used in the following way.

[0088] Patient 50 is put into apnea, or the practitioner asks 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).

[0089] A pre-intervention medical image of patient 50 is acquired while patient 50 is holding their breath. The pre-intervention medical image allows visualization of both the anatomy of interest of patient 50 and the optical tracking device 10. This makes it possible to determine the position of the anatomy of interest relative to the optical tracking device 10 at the point in the respiratory cycle when the patient is holding their breath. Knowing the position of the optical tracking device 10 at that point can then allow the position of the patient's anatomy of interest to be determined in real time. The patient's breathing then resumes normally.

[0090] Pre-intervention medical imaging 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 defined, for example, from an entry point on the patient's skin to a target point on the lesion to be treated.

[0091] In order to insert a medical needle, the patient is placed back in apnea at a time when the position of the optical tracking device 10 is substantially the same as during the acquisition of the pre-intervention medical image (i.e., substantially the same phase of the respiratory cycle). This ensures that the anatomy of interest is substantially in the same position as that represented on the pre-intervention medical image used to plan the intervention.

[0092] During these operations, the practitioner may optionally obstruct the line of sight of one or more optical markers 14 of the optical tracking device 10. As soon as at least one identifiable optical marker 14 is visible to the localization device 40, the position of the optical tracking device 10 can be determined with good accuracy thanks to the redundancy provided by the optical fiber sensor 15 and the measuring device 30. The optical navigation system 20 can also detect unexpected patient movement.

[0093] In some cases, it is necessary to insert several medical instruments (or to insert the same medical instrument several times) to reach different target points at the lesion. The configuration of the tracking device 10 allows this without any particular constraint on the entry point.

[0094] The above description clearly illustrates that, through their various characteristics and advantages, the different devices and methods presented achieve the stated objectives. In particular, the optical tracking device 10 is easy to install, has a minimal footprint in the intervention area, optimizes adhesion to the patient's skin 50, limits the area to be disinfected on the patient's skin 50, and ensures good navigation accuracy even if some optical markers 14 are not visible to the localization device 40.

[0095] It should be noted that the implementation and realization methods considered above have been described as non-limiting examples, and that other variants are therefore conceivable.

[0096] In particular, choosing a specific size, shape, or composition for the base layer 11 of the tracking device 10 is only one variant of the invention. The same applies to choosing a specific shape for the marking region 13, or a specific position for the marking region 13 on the base layer 11. The same also applies to choosing a specific size, shape, or position for the intervention region 12 on the base layer 11.

[0097] As explained above, the optical markers 14 of the tracking device 10 can be either active or passive markers.

[0098] For the optical navigation method 100, various 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 process 100, and the choice of a particular method is only a variant of the invention.

Claims

Demands

1. An optical tracking device (10) for tracking the 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 (1a) intended to be oriented towards the skin of the patient (50) and an outer face (11b) opposite the inner face (1a), said base layer (11) comprising an intervention region (12) corresponding to an opening or a region intended to be cut out to expose an area of ​​the patient's skin (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 (1a), an adhesive material (16) for fixing the optical tracking device (10) to the skin of the patient (50), - on the outer face (11b),at least three optical markers (14) or at least three mounting supports, each intended to accommodate an optical marker (14), - a fiber optic sensor (15) attached to the base layer (11) and having at least one measurement point associated with each of the optical markers (14) or mounting supports, the fiber optic sensor (15) comprising a Bragg grating optical fiber.

2. Optical tracking device (10) according to claim 1 wherein the base layer (11) is a polyethylene sheet lined with a cellulose absorbent sheet.

3. Optical tracking device (10) according to any one of claims 1 to 2 in which the intervention region (12) is pre-cut in the base layer.

4. Optical tracking device (10) according to any one of claims 1 to 3 wherein the base layer (11) has visual indications delimiting the marking region (13).

5. 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 the various points where the optical markers (14) or mounting brackets.

6. 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 radio-opaque markers each rigidly attached 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 wherein 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 optical fiber sensor (15) to determine a relative position of each of the optical markers (14) in a reference frame of the measuring device (30), - a localization device (40) configured to cooperate with the optical markers (14) to determine a position of each of the optical markers (14) in a reference frame of the localization device (40).

11. A method (100) of optical navigation using an optical navigation system (20) according to claim 10, said method (100) comprising: - a determination (101), using the locating device (40), of the position of at least one optical marker (14) visible to the locating device (40), - an identification (102) of said at least one visible optical marker (14) among all the optical markers (14), - a determination (103), using the measuring device (30), 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 localization 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).

12. A method (100) of optical navigation 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).

13. A method (100) of optical navigation 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 any two pairs of optical markers (14) all differ by at least a predetermined margin value, and the method (100) comprises: - a determination (101), using the localization device (40), of the position of at least three optical markers (14) visible to the localization 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).

14. Method (100) of optical navigation according to claim 11 comprising a preliminary generation step, for each marker optical (14), using the localization device (40) and the measuring device (30), of a model representative of a substantially cyclic movement of said optical marker (14), and in which the identification (102) of said at least one visible optical marker (14) is carried out by identifying the model corresponding to the movement of said visible optical marker (14).

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