Position tracking system

Abstract

A signal tracking system comprising: - a fixed element (12) to be fixed to a rigid body part around a target body part of a patient, the fixed element (12) further comprising a mapping element (16); - a tracker element to be fixed to the fixed element (12) to track in real time an internal tracker; - a control unit comprising a memory for storing: an internal reference (R), an image of the target body part and of the at least one fixed element (12), wherein the control unit is designed to define within the internal reference (R) at least one 3D frame position attached to said at least one fixed element (12) and to accurately locate each point of the target body part, the control unit being further designed to accurately locate in real time the internal tracker within the target body part.

Description

Technical Field

[0001] This invention relates to a tracking system and a positioning method for real-time and accurate tracking and positioning of signal emission sources within a patient's body. Background Technology

[0002] In modern medicine, the ability to precisely locate signal transmitting devices inserted into a patient's body in real time to perform surgical procedures or deliver drugs precisely and in a targeted manner is becoming increasingly important.

[0003] For example, this is applicable to gene therapy or cell transplantation, improved tumor resection, and local delivery of antitumor active drugs. For instance, to access challenging deep brain tumors, surgeons are known to require a system capable of positioning millimeter-level devices to precisely reach the surgical site in real time. Furthermore, the already complex medical environment necessitates tracking systems that are “easy to use,” meaning minimally invasive, repeatable, and patient-friendly.

[0004] Furthermore, minimally invasive surgery has been increasingly explored due to the desire to reduce side effects on patients (caused by anesthesia and openings in the body, such as the skull) and the need for precision. Regarding the specific example of the skull, openings can cause cerebrospinal fluid leakage, leading to brain displacement (potentially by several centimeters), thus falsifying the target surgical site (target body part) obtained from preoperative imaging techniques. Therefore, finding alternative solutions to large skull openings is of great significance.

[0005] Reducing invasiveness can be achieved by decreasing the size of the skull opening or even not opening the skull at all. However, in cases where the signal source is located inside the brain, this results in the signal penetrating through layers of the skull. The performance of the positioning system is directly affected by this layer, which increases the depth and attenuation of the signal path. This can be applied to any potentially targeted body part.

[0006] Therefore, the restriction or reduction of body openings leads to a search for signals that can be emitted from inside the patient and correctly read from outside.

[0007] Among known signal tracking techniques, magnetic field technology offers millimeter-level positioning accuracy, unsuitable for locating increasingly prevalent micro-devices. Electromagnetic radio frequency (EMRF) wave technology, limited by its centimeter-level positioning accuracy, also fails to meet the requirements of micro-devices. EM light waves are strongly absorbed in human tissue, severely limiting surgical depth and imposing invasiveness to bypass bone layers. It is well known that exceeding the maximum dose of EM VHF waves can have adverse effects on human tissue. Magnetic resonance imaging (MRI) technology is limited by the inherent trade-off between temporal and spatial resolution. The use of MRI also prohibits the use of magnetic materials, significantly reducing the number of systems that can be embedded. While ultrasound waves experience some attenuation within tissue layers and reflect at interfaces, these limitations are far less severe than those associated with electromagnetic technologies.

[0008] Regarding technological advancements, the ability to locate sub-millimeter-level devices (such as robots or catheter tips) in real time during surgical procedures while maintaining accuracy even under high disturbances is becoming increasingly important. In this context, tracking systems must meet several criteria: human safety, minimal invasiveness, optimal positioning accuracy, the ability to operate throughout the body (especially the brain), real-time operation, and minimal energy consumption.

[0009] For example, in current neuronavigation, surgeons use a well-known external 3D frame of reference and assume that the brain does not move relative to this frame. This external 3D frame is a large, cage-like structure that is screwed into the patient's skull and wraps around the entire head. This large external 3D frame is very bulky, forcing the patient to remain still for extended periods. Therefore, it is uncomfortable to carry. It is also long and difficult to secure to the patient. It also causes some spatial hindrance, which can limit the surgeon's freedom of movement during surgery. However, this external 3D frame allows the surgeon to have a reference point on both MRI and CT imaging, enabling alignment across all images.

[0010] In this application, the 3D frame is defined as a coordinate system, whose origin, orientation, and scale are specified by a set of reference points. Its position is identified mathematically (using numerical coordinate values) and physically (by emitting signals through traditional markers).

[0011] The purpose of this invention is to provide surgeons and patients with a method for safely, accurately, and comfortably aligning different images obtained through different imaging techniques. Summary of the Invention

[0012] Therefore, the present invention relates to a signal tracking system configured to track an internal tracker located within a target body part of a patient, the system comprising:

[0013] - At least one fixation element is designed to be fixed to a rigid body part of the patient, said rigid body part at least partially surrounding the target body part, and the fixation element also includes a mapping element.

[0014] - At least one tracker element configured to be fixed to a fixed element, said at least one sensor element being designed to track the internal tracker in real time.

[0015] - A control unit configured to collect tracking information from at least one tracker element in real time, the control unit also including a memory designed to store:

[0016] oInternal reference,

[0017] o At least one pre-established unique image, which at least shows a portion of the patient's target body part or an element located within the target body part, the pre-established unique image also showing the at least one fixation element and the at least one mapping element, wherein the control unit is designed to define at least one 3D frame position attached to the at least one fixation element within an internal reference, and to precisely position each point of the target body part relative to the 3D frame position.

[0018] The internal reference is defined within a pre-established, unique image that at least shows a portion of the patient's target body part or an element located within the target body part.

[0019] The control unit is also designed to precisely locate the internal tracker within the target body part in real time relative to the position of the at least one 3D frame within an internal reference.

[0020] Thus, this solution achieves the aforementioned objectives. In particular, it is able to register ultrasound tracking information on a single internal reference medical image. It is also able to minimize registration errors by automatically detecting implants within the image.

[0021] The system according to the invention may include one or more of the following features, which may be separate from or combined with each other:

[0022] -The memory is also designed to store:

[0023] oInternal reference,

[0024] o At least one first pre-established image showing the patient's target area.

[0025] o At least one second pre-established image showing a rigid body part, wherein the at least one fixing element and the at least one mapping element are fixed to the rigid body part.

[0026] The internal reference is defined within a first pre-established image, which at least shows a portion of the patient's target body part or elements located within the target body part.

[0027] The control unit is designed to align the at least one first pre-established image and the second pre-established image within an internal reference to define at least one 3D frame position attached to the at least one fixed element within the internal reference, and to precisely locate each point of the target body part relative to the 3D frame position.

[0028] The control unit is also designed to precisely locate an internal tracker within the target body part in real time relative to the position of the at least one 3D frame within an internal reference.

[0029] - The at least one tracker element is configured to be removably fixed to a fixing element.

[0030] - The at least one fixation element is designed to be fixed within a rigid body part of the patient, and the at least one tracker element is also fixed to the fixation element within the rigid body part.

[0031] The system includes at least three tracker elements regularly distributed around the target body part.

[0032] - The at least one fixing element, mapping element, and tracker element are all CT compatible, and the at least one second image is a CT image.

[0033] Both the fixation element and the mapping element are MRI compatible, and the at least one first image is an MRI image.

[0034] -The internal tracker is the signal emission source.

[0035] - The internal tracker is a secondary source, designed to reflect the signal emitted by the primary source.

[0036] -The primary source is outside the target body.

[0037] - The primary source is at least one tracker element.

[0038] -The internal tracker is made by dripping contrast agent from a tiny device.

[0039] - The internal tracker is part of a micro-device.

[0040] The present invention also relates to a signal tracking method configured to locate an internal tracker located within a target body part in an internal reference by means of a tracking system according to any one of the preceding claims, the method comprising the following steps in chronological order:

[0041] -Use at least one fixing element to fix at least one mapping element to a rigid part of the patient's body.

[0042] - Create at least one unique image that shows at least a portion of the patient's target body part or an element located within the target body part, the image also showing the at least one fixation element and the at least one mapping element.

[0043] - Store the at least one unique image in the memory of the control unit.

[0044] - Align the at least one unique image with an internal reference.

[0045] - The position of the at least one mapping element is detected by means of a control unit to determine the position of each fixed element relative to the 3D frame of the internal reference.

[0046] - Secure the tracker components to the mounting components if necessary.

[0047] - Signal to activate the internal tracker

[0048] - The internal tracker can be tracked and located in real time with the help of the control unit.

[0049] The method may include the following steps, which may be independent of or in combination with each other:

[0050] -The method, in chronological order of description, includes the following steps:

[0051] - Create at least one first image displaying the patient's target body part and store it in the memory of the control unit.

[0052] - By means of at least one fixation element, at least one mapping element is fixed to a rigid part of the patient's body.

[0053] - Establish at least one second image displaying a rigid body part, wherein the at least one fixing element and the at least one mapping element are fixed to the rigid body part.

[0054] - By means of a control unit, the at least one first image and the second image are aligned relative to an internal reference.

[0055] - The position of the at least one mapping element is detected by means of a control unit to determine the position of each fixed element relative to the 3D frame of the internal reference.

[0056] - Secure the tracker components to the mounting components if necessary.

[0057] - Signal to activate the internal tracker

[0058] -With the help of the control unit, the internal tracker can be tracked and located in real time.

[0059] The method can also include two additional steps that occur after at least one mapping element is secured to a rigid part of the patient's body by means of at least one fixation element.

[0060] - Create at least one new first image displaying the patient's target body part and replace the previous image in the control unit's memory.

[0061] - Create at least one new second image showing a rigid part of the patient's body and replace the previous image in the control unit's memory.

[0062] - The final step could be: to visualize the internal tracker in real time within the at least first pre-established image or on an image acquired in real time. Attached Figure Description

[0063] Figure 1 It is a perspective view of a system that communicates with the control unit and is regularly fixed to the head of a person around the target body part.

[0064] Figure 2 This is a perspective view of a sensor element according to the present invention.

[0065] Figure 3 This is a perspective view of the fixing element according to the present invention.

[0066] Figure 4 This is a perspective view of the mapping element according to the present invention.

[0067] Figure 5 It is a perspective view of the fixing elements and mapping elements that are fixed to the human skull.

[0068] Figure 6 This is a schematic diagram of the tracking method according to the present invention. Detailed Implementation

[0069] In order to perform surgical procedures including millimeter- or sub-millimeter-scale implantable or importable devices, such as neurosurgery using implantable microrobotic systems or cardiac surgery using catheters, the devices need to be registered on medical imaging for planning and / or real-time monitoring of the procedure.

[0070] In other words, the equipment must be monitored. This is achieved through the signal tracking system 10 of the present invention.

[0071] From a clinical perspective, any patient requires a specific external 3D framing system mounted around the body part to be operated on, particularly in the specific case of brain surgery, where an external 3D framing system is mounted around their head. This external 3D framing system is crucial for tracking millimeter- or sub-millimeter-scale devices, such as miniature robots operating inside the brain. Therefore, the signal tracking system 10 according to the invention comprises:

[0072] - At least one fixation element 12, which is designed to be fixed to a rigid body part 14 of the patient, such as the skull.

[0073] -At least one mapping element 16,

[0074] -At least one tracker element 18,

[0075] -Control unit 20.

[0076] like Figure 1 As shown, to maximize efficiency, the tracking system 10 requires multiple tracker elements 18 distributed around the target body part 22 to create an external 3D framing system. The tracker elements 18 are distributed around the target body part 22 to allow the surgeon to perform surgery in a sufficiently large workspace. In this view, the multiple tracker elements 18 are secured to a rigid body part 14 of the patient surrounding the target body part 22. In the currently described embodiment, the target body part 22 is the patient's brain and multiple tracker elements 18 need to be screwed onto the skull. In the described embodiment, each tracker element 18 includes at least one tracker head 18a and a tracker fixing rod 18b (see...). Figure 2 Each tracking head 18a includes at least one ultrasonic transducer. Thus, similar to a GPS system, the plurality of tracking elements 18 are regularly distributed around the object's head and form a satellite-like implant.

[0077] Each tracker head 18a also communicates continuously in real time with the control unit 20. Therefore, measurement signals are continuously and in real time transmitted from each tracker element 18 to the control unit 20.

[0078] like Figure 2 As shown, in some embodiments, each tracker retaining rod 18b has an external thread that is designed to mate with an internal thread 24 formed within each retaining element 12 (see Figure 1). Figure 3 To secure each tracker element 18 to a rigid body part 14 of the object, the tracking system 10 includes the same number of fixing elements 12. An example of the fixing element 12 is shown in... Figure 3As shown in the diagram. The fixation element 12 is made of well-known biocompatible and inert materials such as PEEK, silicone, or titanium. Each fixation element 12 enables the tracker element 18 and the mapping element 16 to be securely fixed to the patient's skull. In some embodiments, the tracker element 18 is removably fixed to the fixation element 12, and in some other embodiments, they are part of the same component. In any case, fixation of the tracker element 18 to the rigid body part 14 requires incisions into the patient's body, particularly the scalp, which is highly vascularized tissue, thus limiting the number of incisions. Furthermore, the risk of infection increases with the duration of the procedure, especially in neurosurgery, with each incision. Therefore, it is important to allow the fixation element 12 to be quickly fixed with minimal tissue openings. In some alternative embodiments, gluing the fixation element 12 may be an alternative to screwing the fixation element 12 to the rigid body part 14. According to embodiments, the tracker element 18 can be secured above or below the patient's skin: in some embodiments, the securing element 12 is secured within a rigid body part 14 of the patient, and the at least one tracker element 18 is therefore also secured within the rigid body part 14, and thus secured under the skin. This requires drilling a small hole in the rigid body part 14, but the skin can close, thus improving security.

[0079] According to the embodiment, there may be two types of fixing elements 12:

[0080] - Secured to or within a rigid body part 14, meaning that the rigid body part 14 (or a portion thereof) is held between the target body part 22 and the tracker element 18 (in the depicted embodiment, this means that the securing element 12 is screwed onto or glued to the skull), or

[0081] - The fixation element 12 passes through the rigid body part 14, which means that the fixation element 12 passes through the rigid body part 14 and makes the tracker element 18 directly contact the target body part 14 (in the depicted embodiment, this means that the fixation element 12 is twisted through the skull and the tracker element 18 is in direct contact with the brain).

[0082] The direct contact embodiment limits tracking signal attenuation because the tracker element 18 is not separated from the target body part 22 by a rigid body part 14 (in this case, the subject's brain and skull). In this embodiment, and in the embodiment where the fixation element 12 is secured within the rigid body part 14, the surgeon makes a semi-drill hole approximately 1 cm in diameter (maximum 2 cm). However, this posture requires a neuroanesthesiologist to handle undesirable events such as massive hemorrhage or partial skull collapse. In the embodiment without direct contact, the size of the fixation element 12 is limited by the shape of the rigid body part 14, in which case the size of the fixation element 12 is limited by the circular shape of the skull. In the embodiment where the fixation element 12 is secured within the rigid body part 14, the surgeon makes the same type of semi-drill hole approximately 1 cm in diameter (maximum 2 cm) and presents the same constraints and risks as the direct contact embodiment. However, as described above, this embodiment allows for closure of the skin above the fixation element 12 and the tracker element 18, thus improving safety. In embodiments where the fixation element 12 is fixed to a rigid body part 14, in the case of a skull, each fixation element 12 needs to be in contact with the skull and cannot be fixed at a point of high curvature.

[0083] The size of the fixation element 12 is minimized to reduce the size of the screw and thus reduce pressure on the patient. The size of the fixation element 12 should be compatible with local anesthesia, so they have a diameter of 2 cm and a height of 1 cm, especially when the fixation element 12 must be fixed (or embedded) within a rigid body part 14.

[0084] As described above, in order to perform surgical procedures, including those involving millimeter- or submillimeter-scale implantable or introducible devices, these devices need to be registered with medical imaging for planning and / or real-time monitoring of the procedure. To obtain medical imaging, such as for a miniature robot operating within a subject's brain, surgeons typically plan and track the procedure on MRI and / or CT images. Computed tomography (CT) scanners consist of an X-ray tube and a scintillation detector, mounted face-to-face on a rotating gantry. CT scans provide image slices of the target organ through pre-planned translation and rotation of a sensor array.

[0085] Magnetic resonance imaging (MRI) uses signals emitted by moving hydrogen (protons) within the body. Due to their electrical charge, the protons' spin generates a detectable magnetic field. MRI measurements involve three steps:

[0086] - A superconducting magnet creates a fixed external magnetic field that causes a fraction of a million mobile protons to align and reach a low energy state.

[0087] - The transmitting coil generates RF radiation.

[0088] - After RF radiation ceases, protons relax and emit photons at their resonant frequency.

[0089] - Measure the relaxation time constant to obtain MRI images.

[0090] In some cases, such as emergency situations, the surgeon can acquire at least one unique image that shows at least a portion of the patient's target body part 22 or elements located within the target body part 20, as well as the at least one fixation element 12 and the at least one mapping element 16. The control unit 20 can then define at least one 3D frame position attached to the at least one fixation element 12 in a coordinate system (or internal reference R), and thus can precisely position each point of the target body part 22 relative to the 3D frame position.

[0091] Due to the different physiological characteristics of the tissues of the rigid body part 14 and the target body part 22, surgeons spend most of their time planning surgery on MRI and CT images (MRI images for the soft target body part 22, and CT images for the rigid body part 14). These different images can be aligned using a multimodal registration process. According to anyone skilled in the art, the goal of the image registration process is to find the optimal transformation of the alignment-related structures (target body part 22, rigid body part 14, and the external 3D frame formed by the fixation element 12) across the different images. In this invention, the registration process aligns at least one first image (e.g., an MRI image) showing the target body part 22 with at least one second image (e.g., a CT image) showing the rigid body part 14, with the fixation element 12 fixed to the rigid body part 14.

[0092] In some alternative embodiments, the registration process first aligns the at least one first image with an image displaying the rigid body part 14, with the fixing element 12 fixed to the rigid body part 14. The registration process then aligns the two previous images with at least one second image displaying the rigid body part 14, with the fixing element 12 fixed to the rigid body part 14.

[0093] As is well known to anyone skilled in the art, a registration process is an algorithm that converges to a maximum similarity measurement through multiple iterations, aligning the at least two images into a coordinate system (or internal reference R) found in a prior geometric transformation well known in the art. Registration process algorithms use image information to establish a specific measurement called similarity. These algorithms are typically based on voxel intensity, gradient intensity, frequency studies (Fourier space), or statistical information about intensity or features (edges, contours, etc.) in the images to be aligned. Thus, the internal reference R is defined within a pre-established image that at least shows a portion of the target body part 22 of the patient or elements located within the target body part 20.

[0094] Therefore, the present invention enables the definition of an internal reference on a first 3D image of the target body part 22, which is set as a reference and defines / includes an internal reference R.

[0095] The goal of the registration process during surgery is to establish a 3D transformation between an external 3D frame and an internal 3D frame, namely the 3D frame of the target body part 22. According to the invention, as described above, the fixing elements 12 of the plurality of rigid body parts 14 fixed to the object form the external 3D frame. This means that in order to continue the registration process, each fixing element 12 must be precisely detected and its precise position obtained within a predetermined reference R. This reference R can be, for example, the rigid body part 14 or any other element present in one of the images. The reference R may also be an external element defined independently of what is seen on the image. The internal reference R is stored in the memory 26 of the control unit 20. The memory 26 of the control unit 20 also stores:

[0096] -The at least one first image showing the patient's target area 22 (internal 3D frame),

[0097] - The at least one second image shows the rigid body part 14 (external 3D frame) to which the fixing element 12 and the mapping element 16 are fixed, and

[0098] - Any other image that may be used to obtain a clear and precise alignment.

[0099] The control unit 20 runs a registration process algorithm and is therefore designed to align all images within the internal reference R, and is then able to locate each point of the target body part 22 within the internal reference R.

[0100] This image alignment also enables the control unit 20 to establish a 3D frame position within the internal reference R for each fixing element 12. When the control unit 20 aligns the external and internal 3D frames, each 3D frame position is thus defined, as is any point on the target body part 10 within the internal reference R. The 3D frame position of each fixing element 12 is thus clearly established relative to the target body part 10. To allow for direct establishment of 3D frame positions within the internal reference R or to allow the registration process algorithm to run, each fixing element 12 includes a mapping element 16. (As...) Figure 4 As shown, the mapping element 16 includes a mapping head 16a and a connecting rod 16b. In the illustrated embodiment, the mapping element 16 is removably secured to the fixing element 12. In other embodiments, the mapping element 16 and the fixing element 12 form a single piece (not shown). In the illustrated embodiment, each connecting rod 16b has an external thread designed to mate with an internal thread 24 formed within each fixing element 12 (see [link to documentation]). Figure 3 The connecting rod 16b thus cooperates with the fixing element 12 to secure the mapping element 16 to the fixing element 12. Some other embodiments, not shown, are conceivable.

[0101] As in Figure 4 As can be seen, the mapping head 16a has a specific shape that allows for easy identification and positioning of the mapping head 16a and, consequently, easy identification and positioning of the fixed element 12 to which the mapping head 16a is connected. The head 16a of the mapping element 16 is therefore a 3D square reference point.

[0102] In some embodiments, both the mapping element 16 and the tracker element 18 are CT-compatible.

[0103] When each anchor element 12 and the target body part 10 is precisely located within the internal reference R, the control unit 20 and the tracker element 18 precisely locate any internal tracker 28, such as a signal transmitter located within the target body part 22, within the internal reference R in real time. More precisely, this allows the 3D position of the anchor element 12 within the internal reference R to be obtained when at least one anchor element 12 is detected in the image of the target body part. Because each tracker element 18 is attached to each anchor element 12, their 3D positions within the internal reference R can be directly known. Therefore, it is possible to directly track any internal tracker 28 within the internal reference R.

[0104] This enables more direct, reliable, and effective tracking, unlike other systems that require defining at least two references, one about the patient and one about the system itself.

[0105] The internal tracker 28 can also be a signal sensor configured to sense signals emitted by the tracker element 18. In this application, the term "sensor" is understood to mean a receiver. In some embodiments, the internal tracker 28 can be a contrast agent dripped from a microdevice. The contrast agent can be any micro-element about 1 micrometer in size that highly reflects ultrasound waves, such as microbubbles. In some embodiments, the internal tracker 28 can be part of a microdevice that can be manipulated from outside the patient's body.

[0106] When the internal tracker 28 is the signal transmitting source, it can be a primary source (active implantable device) or a secondary source. The secondary source is designed to reflect signals emitted by another primary source. This secondary source can be a passive implantable device, such as a passive microtracker. When the signal transmitting source is a secondary source, the primary source can be located outside the patient's body, and more specifically, the primary source can be one of multiple tracker elements 18 fixed around the target body part 22. In this case, the primary source transmits a signal within the target body part 22, and the signal source reflects this signal back to the tracker element 18 fixed to the rigid body part 14. In the specific case where the tracker element 18 is an ultrasound transducer, one of the tracker elements 18 fixed to the patient's rigid body part 14 (e.g., the skull) transmits ultrasound waves within the target body part 22 (e.g., the patient's brain). In any case, the signal transmitting source emits waves that travel toward the rigid body part 14 into which one or more additional tracker elements 18 are implanted. The time of flight between the initial transmission and reception is used to obtain the distance the wave has traveled. Because multiple tracker elements 18 (at least three) are involved, the 3D position of the transmitted signal source relative to the tracker elements 18 is obtained.

[0107] In the case where the internal tracker 28 is a sensor, it works in a similar manner: the time of flight between the initial transmission and reception from the tracker element 18 is used to obtain the distance the wave has traveled. Since multiple tracker elements 18 are involved (at least three), this allows for the acquisition of the 3D position of the internal tracker 28 relative to the tracker elements 18.

[0108] As any person skilled in the art will know, most tracker elements 18 (e.g., ultrasound transducers) are compatible with CT images but not with MRI images due to their composition. This greatly limits the use of such a system in increasingly MRI-based clinical settings, as MRI typically allows surgeons to examine the status of target body parts 22 during surgery.

[0109] However, because the memory 26 of the control unit 20 stores an accurate image of the target body part 22 aligned with an accurate image of the external 3D frame including the fixing element 12 and the rigid body part 14, the position of the internal tracker 28 can therefore be converted by the control unit 20 into an image displayed to the surgeon on the screen in real time during the operation. The surgeon is thus able to accurately see the internal tracker 28 within the patient's target body part 22.

[0110] The tracking system 10 according to the invention enables surgeons to perform procedures such as Figure 6 The signal localization method is shown. This method allows for the localization of an internal tracker 28 located within a target body part 22 of the patient within an internal reference R. When only a single unique image is required, the method includes the following steps in chronological order:

[0111] -At least one mapping element 16 is fixed to a rigid body part 14 of the patient by means of at least one fixing element 12.

[0112] - Create at least one unique image showing at least a portion of the patient's target body part 22 or elements located within the target body part 22, the image also showing the at least one fixation element 12 and the at least one mapping element 16.

[0113] - Store the at least one unique image in the memory 26 of the control unit 20.

[0114] - Align at least one unique image with an internal reference R.

[0115] - The position of the at least one mapping element 16 is detected by means of the control unit 20 to determine the 3D frame position of each fixing element 12 relative to the internal reference R.

[0116] - If necessary, the tracker element 18 can be secured to the fixing element 12.

[0117] - Signal transmission to activate internal tracker 28

[0118] - The internal tracker 28 is tracked and located in real time with the help of the control unit 20.

[0119] If the quality of the unique image is sufficiently good, the method may include real-time visualization of an internal tracker 28 within at least one pre-established unique image. The internal tracker may also be visualized on the real-time acquired image. This real-time acquired image can be acquired via an external device, such as an ultrasound probe.

[0120] If two or more images are required, the method includes the following steps in chronological order:

[0121] - At least one first image showing the target body part 22 of the patient is created by means of MRI imaging and stored in the memory 26 of the control unit 20.

[0122] - In some cases, at least one additional image showing the patient's rigid body parts 14 is created using CT imaging and stored in the memory 26 of the control unit 20.

[0123] -Design and define the preoperative plan for robotic surgery.

[0124] -At least one mapping element 16 is fixed to a rigid body part 14 of the patient by means of at least one fixing element 12.

[0125] - Establish at least one second image showing a rigid body part 14, on which at least one fixing element 12, at least one mapping element 16, and a tracker element 18 are fixed (if the tracker element 18 and the fixing element 12 are made as a single piece).

[0126] - By means of the control unit 20, at least one first image, a second image, and a third image are aligned with respect to the internal reference R.

[0127] - By means of the control unit 20, the position of at least one mapping element 16 is detected to determine the 3D frame position of each fixed element 12 relative to the internal reference R.

[0128] - In some cases, if the tracker element 18 can be removed from the fixing element, then the tracker element 18 is fixed to the fixing element 12.

[0129] - Signal transmission to activate internal tracker 28

[0130] -The internal tracker 28 is tracked and located in real time using the control unit 20.

[0131] - The internal tracker 28 is visualized in real time within at least a first pre-established image or on an image acquired in real time. This real-time acquired image can be acquired via an external device, such as an ultrasound probe.

[0132] More precisely, after the fixation element 12 is placed, new CT and MRI images are captured and recorded in the memory 26 of the control unit 20 on top of the previous images captured before the fixation element 12 was placed. In these new images, the fixation element 12 is detected and positioned by means of the mapping head 16a of the mapping element 16 fixed to the fixation element 12. This enables the control unit 20 to perform registration between ultrasound tracking and brain images. Since most sensor elements 18 are not MRI compatible, in some embodiments, the sensor element 18 is fixed to the fixation element 12 after the MRI images are established. Therefore, after the registration process, the mapping element 16 is removed from the fixation element 12 (if the mapping element 16 is removable) and replaced by the sensor element 18. In the case where the fixation element 12 and the mapping element 16 form inseparable elements, the tracker element 18 is simply fixed to the fixation element 12. And in the case where the tracker element 18 and the fixation element 12 are made of the same piece, they are both fixed together to the rigid body part 10. According to the embodiment, this means that the tracker element 18 is MRI compatible.

[0133] In addition to registration design, implants can also be used to estimate geometric errors in MRI images as well as registration errors between CT and MRI images.

[0134] After the step of fixing the fixing element 12 to the rigid body part 14:

[0135] -The patient's skin was closed with sutures, or

[0136] - The fixing element 12 is small enough (approximately 2mm to 6mm) to be just covered by the dressing.

[0137] like Figure 1 and Figure 5 As shown, the tracking system 10 is miniature to non-invasive, harmless to the object's body, and provides sub-millimeter accuracy to a depth of 100 mm to 500 mm into the target body part 22 of the object (e.g., the brain), at a frequency higher than 20 Hz.

[0138] The tracking system 10 and positioning method according to the invention improve the comfort and safety of deep surgical interventions. For example, it enables local anesthesia for each fixation element 12, rather than severe general anesthesia.

[0139] Another very important factor is error limitation: the tracking system according to the invention allows bypassing manual setting of the position of the fixed element 12. Furthermore, using the sensor element 18, any internal tracker 28 is directly detected once a signal is transmitted or sensed.

[0140] Finally, the tracking system 10 according to the invention eliminates the need for device-related adjustments, thus reducing the risk of human interference through manual setup (in a 3D-frame-based system). It also eliminates the need for constant image-guided verification and does not rely on the surgeon's hand-eye coordination.

[0141] More precisely, one of the key technical advantages is the creation of a unique reference attached to the patient rather than, for example, the operating room. This allows the patient to be moved without losing the alignment achieved by this invention, unlike other systems that lose this alignment once the patient's body moves relative to an external reference positioned in the operating room.

Claims

1. A signal tracking system (10) configured to track an internal tracker (28) located within a target body part (22) of a patient, said signal tracking system (10) comprising: At least one fixation element (12) is designed to be fixed to a rigid body part of the patient, the rigid body part (14) at least partially surrounding the target body part (22), and the fixation element (12) further includes a mapping element (16). At least one tracker element (18) is configured to be fixed to the fixed element (12), and the at least one tracker element (18) is designed to track the internal tracker (28) in real time. A control unit (20) configured to collect tracking information from the at least one tracker element (18) in real time, the control unit (20) further comprising a memory (26) designed to store: Internal reference coordinate system At least one pre-established unique image that shows at least a portion of the patient’s target body part (22) or an element located within the target body part (22), the pre-established unique image also showing the at least one fixation element (12) and at least one mapping element (16). The internal reference coordinate system is aligned with a coordinate system that displays at least a portion of the target body part (22) of the patient or elements located within the target body part (22). The control unit (20) is designed to define at least one 3D frame position attached to the at least one fixed element (12) within the internal reference coordinate system, and to precisely position each point of the target body part (22) relative to the 3D frame position. The control unit (20) is also designed to precisely locate the internal tracker (28) within the target body part (22) in real time relative to the position of the at least one 3D frame in the internal reference coordinate system.

2. The signal tracking system (10) according to claim 1, wherein, The memory (26) is also designed to store: The internal reference coordinate system At least one first pre-established image showing the patient’s target body part (22). At least one second pre-established image showing the rigid body part (14), the at least one fixing element (12) and the at least one mapping element (16) being fixed to the rigid body part (14), The internal reference coordinate system is defined within a first pre-established image that at least shows a portion of the patient's target body part (22) or elements located within the target body part (22). The control unit (20) is designed to align the at least one first pre-established image and the second pre-established image within the internal reference coordinate system, so as to define at least one 3D frame position attached to the at least one fixed element (12) within the internal reference coordinate system, and to precisely position each point of the target body part (22) relative to the 3D frame position. The control unit (20) is also designed to precisely locate the internal tracker (28) within the target body part (22) in real time relative to the position of the at least one 3D frame in the internal reference coordinate system.

3. The signal tracking system (10) according to claim 1, wherein, The at least one tracker element (18) is configured to be removably fixed to the fixing element (12).

4. The signal tracking system (10) according to claim 1, wherein, The at least one fixation element (12) is designed to be fixed within a rigid body part (14) of the patient, and the at least one tracker element (18) is also fixed to the fixation element (12) within the rigid body part (14).

5. The signal tracking system (10) according to claim 2, wherein, The at least one fixing element (12), mapping element (16) and tracker element (18) are all CT compatible, and the at least one second pre-established image is a CT image.

6. The signal tracking system (10) according to claim 2, wherein, Both the fixation element (12) and the mapping element (16) are MRI compatible, and the at least one first pre-established image is an MRI image.

7. The signal tracking system (10) according to claim 1, wherein, The internal tracker (28) is a signal transmission source.

8. The signal tracking system (10) according to claim 7, wherein, The internal tracker (28) is a secondary source designed to reflect signals emitted by the primary source.

9. The signal tracking system (10) according to claim 8, wherein, The primary source is located outside the object's body.

10. The signal tracking system (10) according to claim 9, wherein, The primary source is the at least one tracker element (18).

11. The signal tracking system (10) according to claim 1, wherein, The internal tracker (28) is a contrast agent dripped by a micro-device.

12. The signal tracking system (10) according to claim 1, wherein, The internal tracker (28) is part of a microdevice.

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