A method for three-dimensional shape reconstruction of a magnetic continuum interventional instrument

Abstract

The application discloses a kind of three-dimensional shape reconstruction methods of magnetic continuum interventional instrument, belong to magnetic interventional medical instrument technical field, comprising the following steps: S1, the magnetic field of magnetic interventional instrument is detected by external sensor;S2, the corresponding relationship model of guide wire magnetic segment magnetic field and its shape is established;S3, fusion intraoperative image and magnetic field information are three-dimensional shape reconstruction.The three-dimensional shape reconstruction method of magnetic continuum interventional instrument described above is used, without additional sensor on interventional instrument, also without changing the mechanical properties of interventional instrument, the shape and position of interventional instrument in patient body can be obtained, and have higher precision.

Description

Technical Field

[0001] This invention relates to the field of magnetic interventional medical device technology, and in particular to a method for three-dimensional morphological reconstruction of a magnetic continuum interventional device. Background Technology

[0002] Currently, stroke is the second leading cause of death and disability worldwide, and the number of stroke patients continues to rise. Acute ischemic stroke (cerebral infarction) and intracranial hemorrhage caused by ruptured aneurysms are the main causes of stroke. Neurointerventional surgery is the primary treatment for these conditions. Doctors observe digital subtraction angiography (DSA) images under X-ray guidance and use guidewires to deliver catheters, microcatheters, and other instruments from the radial or femoral artery opening to the narrowed intracranial vessel or aneurysm, establishing a treatment pathway. Thrombolysis, thrombectomy, or aneurysm embolization are then performed through methods such as infusing thrombolytic agents, releasing thrombectomy stents, and placing coils. The timeliness of stroke treatment and the complexity of cerebrovascular systems place extremely high demands on the ability to deliver instruments effectively. Successful and efficient establishment of interventional treatment pathways is crucial for improving stroke patient survival rates and reducing disability rates.

[0003] In minimally invasive interventional surgery, interventional instruments operate within narrow, closed blood vessels, severely limiting their size and making distal control methods relatively limited. Low-frequency quasi-static magnetic fields are harmless to the human body and possess good remote field control capabilities, making them suitable for precise manipulation of interventional instruments. Unlike conventional interventional instruments, magnetic interventional instruments are made with permanently magnetizable magnetic materials at their distal ends. Under the influence of an external magnetic field, the entire instrument or a portion thereof can deflect or move as needed, achieving controllable tip pointing or positional movement. This reduces the difficulty of superselective vascular branch manipulation and improves the success rate and efficiency of instrument placement. Such magnetic navigation interventional systems comprise two basic elements: magnetic interventional instruments and magnetic field control devices.

[0004] For magnetic interventional devices, to accurately control the device's shape at the next moment using a magnetic field control device, it is necessary to obtain the device's current position and shape in advance. Furthermore, for surgeons, since most interventional surgeries are currently assisted by two-dimensional fluoroscopic imaging, the spatial orientation of the device is unclear. Therefore, surgeons need to make multiple attempts to estimate the device's specific direction and shape based on their tactile sense, significantly increasing the risk of blood vessel rupture and prolonging the operation time. Therefore, being able to directly obtain the shape and position of the entire interventional device can improve the safety and efficiency of the surgery, and also provides the necessary conditions for device navigation.

[0005] The following technical problems are commonly found in existing technologies:

[0006] 1. Interventional devices are located inside the patient's body. Methods based on ordinary fluoroscopic imaging cannot obtain the spatial position of interventional devices inside the patient's body, and cannot establish the specific shape of the devices.

[0007] 2. If an active sensor is added to the interventional device for morphological reconstruction, the passive device is transformed into an active device. The mechanical properties of the device are significantly altered, and there are issues with the sensor wiring, which may interfere with the surgical procedure. Summary of the Invention

[0008] The purpose of this invention is to provide a three-dimensional morphological reconstruction method for magnetic continuum interventional devices. This method can obtain the morphology and position of interventional devices in the patient's body without adding additional sensors to the interventional device or changing the mechanical properties of the interventional device, and it has high accuracy.

[0009] To achieve the above objectives, the present invention provides a method for three-dimensional morphological reconstruction of a magnetic continuum interventional device, comprising the following steps:

[0010] S1. The magnetic field of the magnetic interventional device is detected by an external sensor;

[0011] S2. Establish a model showing the correspondence between the magnetic field of the guide wire's magnetic segment and its morphology;

[0012] S3. Intraoperative images and magnetic field information are integrated to perform three-dimensional morphological reconstruction.

[0013] Preferably, in S1, the magnetic interventional device is a flexible interventional device with a flexible magnetic segment that can be detected by an external magnetic field and fluoroscopic imaging equipment.

[0014] Preferably, in S2, the magnetic segment of the guide wire is equivalent to n cylindrical magnets, with the center of the cylindrical magnet as the origin. In the magnetic cylindrical coordinate system, for a point x(x) in space... s ,y s ,z s ), calculate the magnetic field at point x using the method for calculating the magnetic field of a cylindrical magnet;

[0015] Finite difference finite difference of the magnetic segment of the guide wire transforms the morphological estimation of the entire magnetic segment into the estimation of the pose parameters of n cylindrical magnet segments. For the j-th cylindrical magnet, the parameters that need to be estimated in the spherical coordinate system are (x j y j , z j θ j , φ j The expression for the constructed magnetic field-morphology model is:

[0016]

[0017] Where, x j y j, z j θ is the spatial coordinate of the center of the cylindrical magnet. j , φ j It refers to pitch angle and roll angle. B is used by the sensor to measure the magnetic field. k Calculate the magnetic field for the model.

[0018] Preferably, in S3, the two-dimensional morphology of the magnetic segment of the guide wire needs to be extracted first, and then the magnetic information is fused to reconstruct the three-dimensional morphology.

[0019] Preferably, when extracting the two-dimensional morphology of the magnetic segment of the guide wire, the two-dimensional morphological skeleton of the magnetic segment is obtained by detecting and segmenting the pixels of the magnetic segment of the guide wire in the image.

[0020] Preferably, when performing three-dimensional morphological reconstruction by fusing magnetic information, only the parameters (z'1, θ) are considered. j Estimate the three-dimensional morphology of the magnetic segment of the guidewire by estimating (j = 1, 2, ..., n); first, use the guidewire length as the target against θ. j Make a preliminary estimate.

[0021] Then, the error between the measured magnetic field value at the sensor network and the predicted value of the magnetic field-morphology model is used as the cost function to initially estimate z'1.

[0022] The estimated θ j z'1 as the initial value for parameter θ j A more refined estimate is made using z'1, which represents the magnetic field measurements at the sensor network. The predicted value B(z'1,θ1,…,θ) from the magnetic field-morphology model n Error E B The parameter estimation is performed as a cost function, and the calculation formula is as follows:

[0023]

[0024] Preferably, let L th θ th Let the length change threshold and the angle change threshold be respectively, then the constraint is expressed as:

[0025]

[0026] G jθ =|θ j -θ j-1 |≤θ th ;

[0027] Among them, G L G represents a constraint where the total length changes in a small amount. jθLet the j-th angle change be subject to a limit constraint. The final function is constructed using Lagrange multipliers as follows:

[0028] L(z′1,θ1,…,θ n ) = E B +λ1G L +λ j G jθ (j = 2, 3, ..., n);

[0029] Based on the above function, an optimization algorithm is used to further estimate the target parameters to obtain the final shape of the guidewire.

[0030] Therefore, the beneficial effects of the above-mentioned three-dimensional morphological reconstruction method for a magnetic continuum interventional device in this invention are as follows:

[0031] (1) The shape and position of the interventional device in the patient’s body can be obtained without adding additional sensors to the interventional device or changing the mechanical properties of the interventional device.

[0032] (2) The shape and position of the interventional device can be obtained during the operation without the need for the doctor to perform additional surgical procedures, which is conducive to the safe and efficient operation of the operation.

[0033] (3) Compared with solutions such as embedded optical fibers and electromagnetic sensors, this method does not require the addition of additional signal wires and does not affect the routine surgical procedure.

[0034] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0035] Figure 1 This is a step diagram of an embodiment of a three-dimensional morphological reconstruction method for a magnetic continuum interventional device according to the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of a flexible magnetic tip guidewire according to an embodiment of the three-dimensional morphological reconstruction method of a magnetic continuum interventional device of the present invention, wherein (a) is a structural diagram of the guidewire and (b) is a schematic diagram of the outer layer wrapping material of the guidewire.

[0037] Figure 3 This is a diagram of the magnetic sensor network structure used in an embodiment of the three-dimensional morphological reconstruction method for a magnetic continuum interventional device of the present invention;

[0038] Figure 4 This is an embodiment of the three-dimensional morphological reconstruction method of a magnetic continuum interventional device of the present invention, which divides the magnetic segment into n segments of cylindrical magnets by finite difference. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] Example 1

[0041] like Figure 1 As shown, this invention provides a method for three-dimensional morphological reconstruction of a magnetic continuum interventional device, comprising the following steps:

[0042] S1. The magnetic field of the magnetic interventional device is detected by an external sensor array.

[0043] like Figure 2 As shown in (a), the magnetic interventional device used in this embodiment is a flexible guidewire with a flexible magnetic segment that allows detection by an external magnetic field and fluoroscopic imaging equipment. The inner core of the guidewire uses a nickel-titanium alloy wire with an optimized taper. The guidewire is prepared by heated extrusion and magnetized by a high-voltage pulse circuit. Simultaneously, to reduce friction and improve biocompatibility, a hydrophilic coating is applied to the outermost layer of the guidewire. To ensure clear imaging of the magnetic tip in fluoroscopic images, a radiopaque platinum-iridium coil is wound around the magnetic tip. Figure 2 As shown in (b), the outer layer of the guidewire employs a continuous structure with magnetic nanoparticles dispersed in a polyurethane matrix, and the isotropic design enhances the magnetic response capability. The magnetic nanoparticles are made of NdFeB microparticles coated with silica, which can effectively improve biocompatibility.

[0044] Tests showed that the guidewire performed well in terms of flexibility, torsion control, and tensile fracture resistance, meeting the requirements for clinical use. It also had good magnetic response capabilities, making it suitable for flexible manipulation in small blood vessels.

[0045] like Figure 3 As shown, in this embodiment, a 4×4 magnetic sensor network is designed to obtain the magnetic field information of the above n cylindrical magnets. Other magnetic sensor networks can also be constructed according to actual needs, or other magnetic field sensing devices can be used to sense the magnetic segments of the guide wire.

[0046] S2. Establish a model showing the correspondence between the magnetic field of the guide wire's magnetic segment and its morphology.

[0047] The guidewire tip is a flexible continuum with a complex shape. Compared to a rigid permanent magnet, its magnetic field distribution changes with its shape. Therefore, the shape of the magnetic segment can be estimated using the magnetic field, thus establishing a model of the correspondence between the magnetic field of the guidewire's magnetic segment and its shape. Since the magnetism of any small segment of the guidewire, under any shape, is only related to the magnetization intensity of that segment and is independent of other adjacent guidewire segments, the magnetic segment of the guidewire can be regarded as composed of multiple axially magnetized cylindrical magnets.

[0048] To model the spatial magnetic field generated by the magnetic segment at the end of the guidewire, the magnetic segment of the guidewire is divided into n cylindrical magnets by finite difference, such as... Figure 4As shown. In this embodiment, for a single axially magnetized cylindrical magnet with a height of 2l and a radius of r, its magnetic field is equivalent to a current-carrying solenoid, with an equivalent magnetic moment m = 2lnIπa 2 With the center of the cylindrical magnet as the origin, in the magnetic cylindrical coordinate system, for a point x(x) in space... s ,y s ,z s According to the Biot-Savart law, the magnetic field generated by the surface strips of the solenoid is integrated to calculate the magnetic field at point x. (The modeling of the n cylindrical magnet segments can also be equivalent to a dipole or magnetic ring, or a neural network method can be used to describe and model the magnetic field of each cylindrical magnet segment.)

[0049] Finite difference finite difference of the magnetic segment of the guide wire transforms the morphological estimation of the entire magnetic segment into the estimation of the pose parameters of n cylindrical magnet segments. For the j-th cylindrical magnet, the parameters that need to be estimated in the spherical coordinate system are (x j y j , z j θ j , φ j The expression for the constructed magnetic field-morphology model is:

[0050]

[0051] Where, x j y j , z j θ is the spatial coordinate of the center of the cylindrical magnet. j , φ j It refers to pitch angle and roll angle. B is used by the sensor to measure the magnetic field. k Calculate the magnetic field for the model.

[0052] The three-dimensional attitude of the guidewire is reconstructed by combining the magnetic sensor network built in S1 with the magnetic field-morphology model.

[0053] S3. Intraoperative images and magnetic field information are integrated to perform three-dimensional morphological reconstruction.

[0054] First, the two-dimensional morphology of the magnetic segment of the guidewire needs to be extracted, and then the magnetic information is fused to reconstruct the three-dimensional morphology.

[0055] In the estimation of the magnetic segment of the guidewire, spatial magnetic field information can generally reflect the three-dimensional morphology of the magnetic segment relatively accurately. However, optimizing the estimation using only magnetic field information requires estimating a large number of parameters, and it is difficult to determine the initial values, which has a significant impact on the estimation efficiency and accuracy. On the other hand, using only DSA image information will face the problem of ambiguity in the three-dimensional morphology of the guidewire. Therefore, the image information and magnetic field information are fused, utilizing the inherent permanent magnet properties of the magnetic guidewire. Thus, no additional processing of the guidewire is required during estimation, avoiding the need to add additional sensors to the guidewire, which would turn the guidewire from passive to active, causing signal wires on the guidewire and resulting in blind end closure problems, as well as the loss of guidewire performance due to the addition of sensors.

[0056] Therefore, when performing three-dimensional morphology estimation of the guidewire, the two-dimensional morphology of the guidewire in the two-dimensional fluorescence fluoroscopic image can be extracted to form morphological prior information, which is provided to the morphology estimation algorithm through the magnetic field, thereby improving the computational efficiency and the accuracy of the estimation results. Moreover, DSA image is an image modality that must be used during the operation, and it will not add extra burden to the equipment and operation.

[0057] When extracting the two-dimensional morphology of the magnetic segment of the guide wire, the first step is to detect the target and segment the pixels of the magnetic segment of the guide wire. Then, key points are extracted from the start and end points of the magnetic segment of the guide wire. Finally, the skeleton of the pixel part of the magnetic segment of the guide wire is extracted.

[0058] In this embodiment, when performing target detection at the head end of the guide wire magnetic segment, the RTMDet target detector is used. For the task of segmenting the guide wire magnetic segment, the DeepLabv3+ model is used to perform segmentation within the target detection range. After completing target detection and pixel segmentation of the guide wire magnetic segment, keypoint identification of the start and end points of the magnetic segment is required to accurately obtain the magnetic segment portion. In this embodiment, RTMPose is used as the keypoint identification model for keypoint identification. When extracting the skeleton of the guide wire magnetic segment pixels, the Zhang-Suen algorithm is used. After extracting the skeleton pixels, the pixel closest to the start point of the magnetic segment is found as the start point of the magnetic segment skeleton, and the end point pixels are added to the skeleton to form the final guide wire magnetic segment skeleton.

[0059] When fusing magnetic information for 3D morphological reconstruction, since the 2D morphological information of the guidewire can be obtained from the perspective image, the relevant pose parameters can be directly obtained. Let this be the height of the base of the j-th cylindrical magnet. Since the height of the base of the (j+1)-th cylindrical magnet can be derived from the height of the base of the j-th cylindrical magnet, only the parameters (z'1, θ) are considered. j By estimating (j=1,2,…,n), the three-dimensional morphology of the magnetic segment of the guide wire can be obtained.

[0060] First, the guidewire length is used as the target pair θ. j A preliminary estimate is made, and then the error between the measured magnetic field value and the predicted value of the magnetic field at the sensor network and the magnetic field-morphology model is used as the cost function to initially estimate z'1. Finally, the estimated θ is used to... j z'1 as the initial value for parameter θ j A more refined estimate is made using z'1, which represents the magnetic field measurements at the sensor network. The predicted value B(z'1,θ1,…,θ) from the magnetic field-morphology model n Error E B The parameter estimation is performed as a cost function, and the calculation formula is as follows:

[0061]

[0062] Similarly, because the magnetic segment exhibits minimal length change and minimal overall bending during operation, the optimized parameters need to satisfy two nonlinear constraints. Let L... th θ th Let the length change threshold and the angle change threshold be respectively, then the constraint is expressed as:

[0063]

[0064] G jθ =|θ j -θ j-1 |≤θ th ;

[0065] Among them, G L G represents a constraint where the total length changes in a small amount. jθ This indicates that the change in the j-th angle has certain constraints. Using Lagrange multipliers, the final function is constructed as follows:

[0066] L(z′1,θ1,…,θ n ) = E B +λ1G L +λ j G jθ (j = 2, 3, ..., n);

[0067] Based on the above function, an optimization algorithm is used to further estimate the target parameters to obtain the final shape of the guidewire.

[0068] Therefore, the present invention employs the above-mentioned three-dimensional morphology reconstruction method for a magnetic continuum interventional device, which can obtain the morphology and position of the interventional device in the patient's body without the need to install additional sensors on the interventional device or change the mechanical properties of the interventional device, and has high accuracy.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for three-dimensional morphological reconstruction of a magnetic continuum interventional device, characterized in that, Includes the following steps: S1. The magnetic field of the magnetic interventional device is detected by an external sensor; S2. Establish a model showing the correspondence between the magnetic field of the guide wire's magnetic segment and its morphology; S3. Integrate intraoperative images and magnetic field information to perform three-dimensional morphological reconstruction; In S2, the magnetic segment of the guidewire is equivalent to... n A cylindrical magnet, with its center as the origin, has a coordinate system in which it represents a point in space. Calculate the magnetic field at point x using the method for finding the magnetic field of a cylindrical magnet; The morphological estimation of the entire magnetic segment is transformed into the estimation of the pose parameters of the nth cylindrical magnet segment. For the ... j The parameters that need to be estimated for each cylindrical magnet are: The expression for the constructed magnetic field-morphology model is: ； ； in, These are the spatial coordinates of the center of the cylindrical magnet. It refers to pitch angle and roll angle. For the sensor to measure the magnetic field, Calculate the magnetic field for the model; In S3, the two-dimensional morphology of the magnetic segment of the guidewire needs to be extracted first, and then the magnetic information is fused to reconstruct the three-dimensional morphology. When fusing magnetic information for 3D morphological reconstruction, only the parameters are considered. Enter The three-dimensional morphology of the magnetic segment of the guidewire is estimated; firstly, the guidewire length is used as the target pair. Make a preliminary estimate. Then, the error between the measured magnetic field value and the predicted value of the magnetic field at the sensor network and the magnetic field-morphology model is used as the cost function to initially estimate the error. , The estimated and As initial value for parameters and To make a more refined estimate, the magnetic field measurements at the sensor network will be... Predictions from the magnetic field-morphology model error The parameter estimation is performed as a cost function, and the calculation formula is as follows: 。 2. The method for three-dimensional morphological reconstruction of a magnetic continuum interventional device according to claim 1, characterized in that: In S1, the magnetic interventional device is a flexible interventional device with a flexible magnetic segment that can be detected by an external magnetic field and fluoroscopic imaging equipment.

3. The method for three-dimensional morphological reconstruction of a magnetic continuum interventional device according to claim 1, characterized in that: When extracting the two-dimensional morphology of the magnetic segment of the guide wire, the two-dimensional morphological skeleton of the magnetic segment is obtained by detecting and segmenting the pixels of the magnetic segment in the image.

4. The method for three-dimensional morphological reconstruction of a magnetic continuum interventional device according to claim 1, characterized in that: set up , Let the length change threshold and the angle change threshold be respectively, then the constraint is expressed as: ； ； in, Constraints that indicate a small change in total length. Indicates the first j The angular changes are constrained, and the final function is constructed using Lagrange multipliers: ； Based on the above function, an optimization algorithm is used to further estimate the target parameters to obtain the final shape of the guidewire.

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