CN117224208B

CN117224208B - Interventional magnetic navigation system and navigation method under ultrasonic guidance

Info

Publication number: CN117224208B
Application number: CN202311163806.8A
Authority: CN
Inventors: 王健发; 吕逸飞; 程嘉; 王人成; 季林红
Original assignee: Beijing Sonop Technology Co ltd; Tsinghua University
Current assignee: Beijing Sonop Technology Co ltd; Tsinghua University
Priority date: 2023-09-11
Filing date: 2023-09-11
Publication date: 2024-03-12
Anticipated expiration: 2043-09-11
Also published as: CN117224208A

Abstract

The ultrasonic probe is used for acquiring an ultrasonic image, the magnetic sensor unit is arranged in the ultrasonic probe and is used for acquiring an environment magnetic field vector and a magnetic field generated by a magnetic interventional needle, and the ultrasonic image and the magnetic field vector are sent to the operation unit to calculate the pose of the magnetic interventional needle and generate an ultrasonic image containing the pose information of the interventional needle. In the method, the magnitude of an environmental magnetic field is acquired before navigation is started, a magnetic field vector is acquired in real time after navigation is started, the estimated direction of the environmental magnetic field is calculated, the midpoint position of the magnetic intervention needle is estimated based on a magnetic gradient tensor method, the estimated midpoint position is taken as an initial value, the needle point position and the needle tail position of the magnetic intervention needle are calculated based on a least square method and a magnetic field model of the magnetic intervention needle, and finally an ultrasonic image containing the pose of the magnetic intervention needle is generated. The real-time high-precision positioning of the interventional needle can be realized, the difficulty of intervention is reduced, and the success rate of the intervention is improved.

Description

Interventional magnetic navigation system and navigation method under ultrasonic guidance

Technical Field

The disclosure relates to the technical field of medical instruments, in particular to an interventional magnetic navigation system and a navigation method under ultrasonic guidance.

Background

Interventional therapy is a common practice in clinical diagnosis and treatment that requires the physician to accurately insert needles, catheters, and other devices into the target tissue of the patient, such as peripheral nerve blocks for surgical anesthesia or post-operative analgesia. Because the equipment used in the interventional therapy is slender and has smaller size, and a doctor cannot directly observe the condition in a patient, the accuracy of the interventional therapy is very dependent on the knowledge and experience of the doctor, and if the relative spatial position relationship between a target tissue and the interventional equipment can be provided for the doctor, the interventional difficulty is greatly reduced, and the interventional success rate is improved.

Ultrasound imaging, which is a real-time imaging technique, can present images of tissue within a patient's body to a physician in real-time and is therefore often used to guide interventional procedures. However, the ultrasonic imaging technology can only image things in the imaging plane, and when the interventional needle is not strictly positioned in the imaging plane, the ultrasonic imaging result cannot display the interventional needle image or only can display part of the interventional needle image, so that a doctor cannot accurately judge the position of the interventional needle and even misjudgment is generated.

The navigation system can acquire the accurate position of the interventional needle in real time, and the existing navigation methods are divided into two types:

The first is a mechanical limiting method, wherein a mechanical device is used for limiting the movable range of the interventional needle in an ultrasonic imaging plane, so that the image of the interventional needle can be completely displayed on an ultrasonic image. Such methods are generally simple in structure and small and portable in device, but because the mechanical device is not changeable in size, a single mechanical device can only be applied to an interventional needle and an ultrasonic probe with specific sizes, and meanwhile, the degree of freedom of the interventional needle is limited, so that a navigation system based on a mechanical limiting method is very cumbersome to use and has low flexibility. A puncture needle holder as disclosed in patent CN101756715a can be directly clamped on an ultrasonic probe, and at this time, a puncture needle placed on the puncture needle holder is strictly in an ultrasonic imaging plane, but the puncture needle has only two degrees of freedom of movement, one is a degree of freedom of displacement along the axial direction of the puncture needle, and the other is a degree of freedom of rotation about the rotation axis of the puncture needle holder, so that it is very difficult to adjust the position of the puncture needle during use, and a user is required to have a lot of experience.

The second is an external positioning system, a sensing device is arranged on the ultrasonic probe and the interventional needle, the external positioning system is utilized to acquire the space pose of the ultrasonic probe and the interventional needle in real time, and output equipment such as a display screen is utilized to provide pose information of the interventional needle for doctors. The common external positioning system comprises an optical positioning system, an electromagnetic positioning system and the like, the method does not need to limit the motion freedom degree of the interventional needle, and has lower medical quality requirements on users, but a special puncture needle containing a sensor is usually needed, so that the cost is increased, and meanwhile, the space occupation of positioning equipment is high and the portability requirements of ultrasonic imaging equipment are contradictory. As disclosed in US patent application 20190090956A1, a puncture navigation system in which an electromagnetic field generating device is mounted on an ultrasonic probe, a magnetic field measuring sensor is mounted on a puncture needle, the relative pose relationship between the ultrasonic probe and the puncture needle is calculated by the magnetic field, and in which a user can freely move the ultrasonic probe and the puncture needle without restriction while observing the real-time position of the puncture needle, but the navigation system is only suitable for a puncture needle of a specific size and specification because of the need to acquire the relative pose relationship between the sensor and the puncture needle, and the electromagnetic field generating device outside the ultrasonic probe also affects the operation of a doctor.

As another example, patent CN103945772a provides an imaging probe and a method for obtaining position and/or direction information, by installing a magnetometric detector inside the ultrasound probe and magnetizing the interventional device with a magnetizing device, the position of the interventional device relative to the ultrasound probe can be calculated from the magnetic field generated by the interventional device. This approach does not require additional sensors to be installed on the interventional device, and therefore does not place excessive demands on the specifications and size of the medical device, and does not affect the physician's operation. The Jeff Gadsden et al paper Evaluation of the eZono 4000with eZGuide for ultrasound-guided procedures has carried out experimental tests on products adopting the technical scheme of patent CN103945772A, and experimental results show that the products can effectively reduce the difficulty of puncture and improve the puncture speed and efficiency, however, the positioning accuracy of the navigation system is +/-2.5 mm, and when the interventional target volume is smaller, the products are difficult to meet the accurate positioning requirement.

In view of the foregoing, it is necessary to design an interventional magnetic navigation system and method under ultrasound guidance, which has high positioning accuracy, high flexibility, and convenient use and operation.

Disclosure of Invention

In view of the foregoing, it is necessary to provide an interventional magnetic navigation system and a navigation method under ultrasound guidance, which are used for overcoming the problem that the positioning accuracy, flexibility and portability of the interventional navigation system in the prior art are difficult to be compatible.

To solve the above technical problem, an interventional magnetic navigation system under ultrasound guidance provided in a first aspect of the present disclosure includes:

the ultrasonic probe is used for acquiring an ultrasonic image;

the magnetic sensor unit is fixed on the ultrasonic probe and used for acquiring magnetic field vectors, the magnetic sensor unit comprises a plurality of magnetic sensor arrays, the centers of any 2 magnetic sensor arrays are not overlapped, each magnetic sensor array comprises 4 magnetic sensors which are positioned on the same plane and in the same direction, and the central connecting lines of the 4 magnetic sensors form a rectangle;

a magnetic interventional needle, a portion of which can be inserted into human tissue, the portion of which is magnetized to generate a stable and constant magnetic field;

the operation unit is used for estimating the midpoint position of the magnetic intervention needle based on a magnetic gradient tensor method according to the parameters of the magnetic sensor unit obtained through calibration and the magnetic field vector obtained by the magnetic sensor unit in a navigation working state, taking the midpoint position as an initial value, calculating the needle point position and the needle tail position of the magnetic intervention needle based on a least square method and a magnetic field model of the magnetic intervention needle, and generating an ultrasonic image containing the pose information of the magnetic intervention needle according to the ultrasonic image, the needle point position and the needle tail position of the magnetic intervention needle and the parameters of the magnetic sensor unit and the ultrasonic probe; and

The display device is used for displaying the ultrasonic image containing the magnetic interventional needle pose information.

In some embodiments, the parameters of the magnetic sensor unit include correction coefficients of each magnetic sensor in the magnetic sensor unit and relative pose relationships between each magnetic sensor, and the parameters of the magnetic sensor unit and the ultrasonic probe include relative pose relationships between the magnetic sensor unit and the ultrasonic probe.

In some embodiments, the mathematical expression of the magnetic field model of the magnetic interventional needle is:

wherein, ^T B _r in coordinates for magnetic interventional needle ^T P _r A magnetic field vector generated thereat; ^T P _p and ^T P _n the needle point position coordinates and the needle tail position coordinates of the magnetic interventional needle are defined as projection positions of the needle point and the needle tail of the magnetic interventional needle on the axis of the magnetic interventional needle respectively; ^T P _t tip coordinates for a magnetic interventional needle; alpha is the axial rotation angle of the magnetic interventional needle, and is defined as an included angle between the connecting line of the needle tip position and the needle tip and the shortest distance direction from the origin of the coordinate system of the magnetic sensor unit to the axis of the magnetic interventional needle; m is M _n Magnetic coercivity for a magnetic interventional needle; r and l _t The radius and the needle tip length of the magnetic interventional needle are respectively; θ is the angle of rotation about the axis of the magnetic interventional needle in the integration path.

In some embodiments, the computing unit estimates the magnetic interventional needle midpoint location based on a magnetic gradient tensor method, comprising:

obtaining an environment magnetic field estimation direction according to a magnetic field vector obtained by a magnetic sensor unit and a relative pose relation among magnetic sensors in the magnetic sensor unit, and estimating the midpoint position of the magnetic interventional needle based on a magnetic gradient tensor method; the magnetic field vector obtained by the magnetic sensor unit is a magnetic field vector generated by adding an ambient magnetic field vector obtained by placing the magnetic sensor unit in a use environment and placing the magnetic interventional needle outside the detection range of the magnetic sensor unit and the magnetic field generated by the magnetic interventional needle.

In some embodiments, the obtaining the estimated direction of the environmental magnetic field according to the magnetic field vector obtained by the magnetic sensor unit and the relative pose relationship between the magnetic sensors in the magnetic sensor unit, and estimating the midpoint position of the magnetic interventional needle based on a magnetic gradient tensor method specifically includes:

taking the average value of magnetic field vectors acquired by magnetic sensors in the magnetic sensor unit as an average ambient magnetic field vector According to the mean ambient magnetic field vector +.>Calculating the estimated direction of the environmental magnetic field +.>

Calculating magnetic gradient tensor of the center of each magnetic sensor array according to the magnetic field vector obtained by the magnetic sensor unit and the relative pose relation of each magnetic sensor in the magnetic sensor unit ^T G _O And average magnetic field vector ^T B _O ；

From the magnetic gradient tensor in the center of the magnetic sensor array ^T G _O And average magnetic field vector ^T B _O The midpoint position of the magnetic interventional needle is calculated as follows ^T P _M ：

Wherein N is _r For the number of the magnetic sensor arrays in the magnetic sensor unit, m and N are not more than N _r Is a positive integer of (a) and (b), ^T G _Om 、 ^T B _Om and ^T P _Om the magnetic gradient tensor, the average magnetic field vector and the position coordinate of the center of the mth magnetic sensor array in the magnetic sensor unit are respectively, ^T G _On 、 ^T B _On and ^T P _On the magnetic gradient tensor, the average magnetic field vector and the position coordinate of the center of the nth magnetic sensor array in the magnetic sensor unit are respectively.

In some embodiments, the interventional magnetic navigation system further comprises a calibration unit for calibrating parameters of the magnetic sensor unit and the ultrasound probe before navigating the operational state, the calibration unit comprising:

the calibration support comprises a calibration support body, an ultrasonic probe placing hole, a plurality of electromagnet mounting holes, an N-shaped line mounting hole and an acoustic guide medium accommodating cavity, wherein the ultrasonic probe placing hole is formed in the calibration support body, and the ultrasonic probe containing the magnetic sensor unit is placed in the ultrasonic probe placing hole;

The electromagnets are arranged in a corresponding electromagnet mounting hole and uniformly distributed around the magnetic sensor unit, and a magnetic field generated by the electromagnets can be acquired by the magnetic sensor unit;

the N-shaped lines are arranged in the N-shaped line mounting holes and are intersected with the imaging plane of the ultrasonic probe, the N-shaped lines comprise a plurality of N-shaped structures, two straight lines in the N-shaped structures are in parallel relation, and at least one straight line is perpendicular to the imaging plane of the ultrasonic probe;

the sound guide medium is filled in the sound guide medium accommodating cavity, so that the sound guide medium exists in the imaging range of the ultrasonic probe, and the N-shaped line completely passes through the sound guide medium;

and the calculating module is used for calculating the relative pose relation between the magnetic sensors in the magnetic sensor unit and the relative pose relation between the magnetic sensor unit and the ultrasonic probe.

In some embodiments, the number of electromagnets should be no less than 4, and the electromagnets can generate the same or approximately the same magnetic field.

In some embodiments, before calibration, obtaining correction coefficients for each magnetic sensor in the magnetic sensor unit based on an ellipsoid fitting method;

In the calibration process, an ultrasonic probe comprising the magnetic sensor unit is placed in the ultrasonic probe placing hole, all electromagnets are turned on and off one by one, only one electromagnet is turned on each time, and each magnetic field vector is recorded; according to the magnetic field vector of each time, calculating the relative pose relation between each magnetic sensor in the magnetic sensor unit and the calibration support main body based on a least square method, and calculating the relative pose relation between each magnetic sensor in the magnetic sensor unit; acquiring an ultrasonic image by using the ultrasonic probe, wherein the ultrasonic image comprises the sound guide medium and the N-shaped line section; selecting the central position of the N-shaped line section from the ultrasonic image; according to the central position of the N-shaped line section and the relative pose relation between each magnetic sensor in the magnetic sensor unit and the calibration support main body, calculating the relative pose relation between the ultrasonic probe and the calibration support main body, and calculating the relative pose relation between the ultrasonic probe and the magnetic sensor unit.

A second aspect of the present disclosure provides a navigation method of an interventional magnetic navigation system according to any one of the embodiments of the first aspect of the present disclosure, comprising the steps of:

Step 1: before navigation is started, the magnetic interventional needle is placed outside the detection range of the magnetic sensor unit, an environment magnetic field vector is obtained by the magnetic sensor unit, and the environment magnetic field size is calculated according to the environment magnetic field vector;

step 2: after navigation is started, the magnetic sensor unit acquires a magnetic field vector generated by adding an ambient magnetic field vector and a magnetic field generated by the magnetic interventional needle;

step 3: obtaining an environment magnetic field estimation direction according to the magnetic field vector obtained in the step 2 and the relative pose relation among the magnetic sensors in the magnetic sensor unit, and estimating the midpoint position of the magnetic interventional needle based on a magnetic gradient tensor method;

step 4: taking the midpoint position of the magnetic intervention needle and the estimated direction of the environmental magnetic field as initial values, and calculating the needle tip position and the needle tail position of the magnetic intervention needle based on a least square method and a magnetic field model of the magnetic intervention needle;

step 5: acquiring an ultrasonic image by using the ultrasonic probe;

step 6: and generating an ultrasonic image containing the pose of the magnetic interventional needle according to the needle point position and the needle tail position of the magnetic interventional needle, the ultrasonic image and the relative pose relation between the magnetic sensor unit and the ultrasonic probe.

In some embodiments, calibrating parameters of the magnetic sensor unit and the ultrasonic probe with the calibration unit is further included before step 1;

before calibration, acquiring correction coefficients of each magnetic sensor in the magnetic sensor unit based on an ellipsoid fitting method;

Compared with the prior art, the beneficial effects of the present disclosure include:

the interventional magnetic navigation system under the ultrasonic guidance is flexible and portable, and the magnetic sensor unit for positioning the magnetic interventional needle is integrated inside the ultrasonic probe, so that the size of the ultrasonic probe is basically unchanged, no external equipment is arranged at the same time, the portability of the ultrasonic imaging equipment is still provided, and the use habit of doctors is reserved. On the other hand, the navigation system performs positioning by measuring the magnetic field vector, the positions of the ultrasonic probe and the magnetic interventional needle are not limited in the using process, and the navigation system has higher flexibility in the using process.

According to the interventional magnetic navigation method under ultrasonic guidance, the magnetic sensor unit comprises a plurality of magnetic sensor arrays distributed in a rectangular mode, so that calculation of magnetic gradient tensors is facilitated, the magnetic interventional needle position can be estimated rapidly based on the magnetic gradient tensor method, the follow-up least square method is enabled to calculate an initial value close to a global optimal result, and convergence to a local optimal solution is avoided. The position and the direction of the magnetic intervention needle can be accurately calculated based on the least square method and the magnetic field model of the magnetic intervention needle, and an ultrasonic image containing the pose of the magnetic intervention needle is generated, so that the magnetic intervention needle is positioned in real time and high precision.

Furthermore, the interventional magnetic navigation method under the ultrasonic guidance can realize the rapid and accurate calibration of the magnetic sensor unit and the ultrasonic probe through calibration, can calibrate two pose parameters of the relative pose relation between the magnetic sensors in the magnetic sensor unit and the relative pose relation between the magnetic sensor unit and the ultrasonic probe, is simple to operate and high in precision, and further improves the positioning precision of the magnetic interventional needle in the navigation process.

Drawings

FIG. 1 is a schematic diagram of an embodiment of an interventional magnetic navigation system under ultrasound guidance provided by the present disclosure in a navigation operating state;

FIG. 2 is a schematic diagram of an embodiment of an interventional magnetic navigation system under ultrasound guidance provided by the present disclosure in a nominal operating state;

FIG. 3 is a schematic diagram of an embodiment of a magnetic sensor array according to the present invention;

FIG. 4 is a schematic diagram of an embodiment of a calibration unit in an interventional magnetic navigation system provided by the present disclosure;

FIG. 5 is a schematic diagram illustrating a cross-sectional front view of an embodiment of a calibration unit in an interventional magnetic navigation system according to the present disclosure;

FIG. 6 is a schematic side view of an embodiment of a calibration unit in an interventional magnetic navigation system according to the present disclosure;

FIG. 7 is a schematic diagram of a cross-sectional plane structure of an N-type line of an embodiment of a calibration unit in an interventional magnetic navigation system provided by the present disclosure;

FIG. 8 is a flow chart of an embodiment of an interventional magnetic navigation method under ultrasound guidance provided by the present disclosure;

fig. 9 is a flowchart of an embodiment of step S801 in fig. 8 provided in the present disclosure;

FIG. 10 is a schematic diagram of dimension parameters of an embodiment of an N-wire in a calibration unit of an interventional magnetic navigation system provided by the present disclosure;

fig. 11 is a flowchart of an embodiment of step S804 in fig. 8 provided in the present disclosure;

FIG. 12 is a schematic view of the magnetic interventional needle tip position, needle tail position, axial rotational angle.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

On the contrary, the application is intended to cover any alternatives, modifications, equivalents, and variations as may be included within the spirit and scope of the application as defined by the appended claims. Further, in the following detailed description of the present application, specific details are set forth in order to provide a more thorough understanding of the present application. The present application will be fully understood by those skilled in the art without a description of these details.

The structures, proportions, sizes, etc. shown in the drawings are shown only in connection with the present disclosure, and should not be construed as limiting the scope of the invention, since any structural modifications, proportional changes, or dimensional adjustments, which may be made by those skilled in the art, should not be construed as limiting the scope of the invention without affecting the efficacy or the achievement of the objective of the invention. Also, the terms such as "upper," "lower," "left," "right," "middle," and "a" and the like recited in the present specification are merely for descriptive purposes and are not intended to limit the scope of the present application to which they may be applied, but rather to modify or adapt the relative relationship without materially altering the technical context.

An embodiment of the present disclosure provides an interventional magnetic navigation system under ultrasound guidance, and as shown in fig. 1 and fig. 2, fig. 1 is a schematic structural diagram of an embodiment of the interventional magnetic navigation system under ultrasound guidance provided in the first aspect of the present disclosure in a navigation working state, and fig. 2 is a schematic structural diagram of an embodiment of the interventional magnetic navigation system under ultrasound guidance provided in the first aspect of the present disclosure in a calibration working state, where the system includes an ultrasound probe 1, a magnetic sensor unit 2, a magnetic interventional needle 3, an operation unit 4, a display device 5, and a calibration unit 6. Wherein:

The ultrasonic probe 1 is a medical ultrasonic probe, and can acquire an ultrasonic image in real time.

The magnetic sensor unit 2 comprises a plurality of magnetic sensor arrays, each magnetic sensor array comprises 4 magnetic sensors which are positioned on the same plane and in the same direction, such as magneto-impedance magnetic sensors, the magnetic field vector can be obtained in real time, the central connecting line of the 4 magnetic sensors forms a rectangle, the centers of any 2 magnetic sensor arrays are not coincident, i.e. the coordinates of the intersection points of the diagonal lines of the rectangle are different. FIG. 3 is an embodiment of a magnetic sensor array. The magnetic sensor unit 2 is mounted and fixed on the ultrasonic probe 1, that is, the relative pose relationship of the ultrasonic probe 1 and the magnetic sensor unit 2 is always kept unchanged. The installation position of the magnetic sensor unit 2 should be close to the head of the ultrasound probe 1, i.e., should be close to the position where the ultrasound image is located.

The magnetic interventional needle 3 is a magnetized medical interventional needle, and the medical interventional needle is magnetized by means of a permanent magnet or an electromagnet and the like, so that a constant magnetic field is generated at the part of the magnetic interventional needle 3 inserted into human tissue.

The arithmetic unit 4 includes a central processing unit, a memory, and other elements, and is connected to the ultrasonic probe 1 and the magnetic sensor unit 2 in a wireless or wired communication manner, and receives ultrasonic image data transmitted from the ultrasonic probe 1 and magnetic field vector data transmitted from the magnetic sensor unit 2. In a calibration working state, the operation unit 4 calculates correction coefficients and relative pose relations of each magnetic sensor in the magnetic sensor unit 2 and relative pose relations of the magnetic sensor unit 2 and the ultrasonic probe 1 according to the received data, and stores the results in navigation calculation; in the navigation working state, the operation unit 4 calculates the needle tip position and the needle tail position of the magnetic intervention needle 3 based on a magnetic gradient tensor method and a magnetic field model of the magnetic intervention needle according to the relative pose relation among the magnetic sensors in the magnetic sensor unit 2 and the magnetic field vector obtained by the magnetic sensor unit 2, then generates an ultrasonic image containing magnetic intervention needle pose information according to the ultrasonic image acquired by the ultrasonic probe 1 in real time, the needle tip position and the needle tail position of the magnetic intervention needle 3 and the relative pose relation between the magnetic sensor unit 2 and the ultrasonic probe 1, and finally sends the generated ultrasonic image containing magnetic intervention needle pose information to the display device 5 for display.

The display device 5 includes a display screen, interactive keys, etc., for man-machine interaction and information transfer, and the arithmetic unit 4 is installed and fixed in the display device 5 and controls the operation of the display device 5.

In order to further improve the positioning accuracy of the magnetic interventional needle during the navigation, the interventional magnetic navigation system according to the first aspect of the present disclosure further comprises a calibration unit 6 for calibrating the relative pose relationship between the magnetic sensors in the magnetic sensor unit 2 and the relative pose relationship between the magnetic sensor unit 2 and the ultrasound probe 1. Referring to fig. 4 to 7, fig. 4 is a schematic structural diagram of an embodiment of a calibration unit 6 in an interventional magnetic navigation system according to the first aspect of the present disclosure, fig. 5 is a schematic structural diagram of a front cross-section of an embodiment of a calibration unit 6 in an interventional magnetic navigation system according to the first aspect of the present disclosure, fig. 6 is a schematic structural diagram of a side cross-section of an embodiment of a calibration unit 6 in an interventional magnetic navigation system according to the first aspect of the present disclosure, and fig. 7 is a schematic structural diagram of a plane cross-section of an N-line of an embodiment of a calibration unit 6 in an interventional magnetic navigation system according to the first aspect of the present disclosure; the calibration unit 6 comprises a calibration support, a number of electromagnets 62, an N-shaped line 63, an acoustic guiding medium 64 and a calculation module (not shown in the figure). Wherein:

The calibration support comprises a calibration support body 61, and an ultrasonic probe placing hole 611, a plurality of electromagnet mounting holes, an N-shaped line mounting hole and an acoustic guide medium accommodating cavity which are formed in the calibration support body 61; the calibration support body 61 is made of non-ferromagnetic material, such as aluminum, acryl, etc., to avoid interference with the magnetic field. An ultrasonic probe placement hole 611 is formed at the center of the upper half of the index holder body 61 for placing the ultrasonic probe 1 including the magnetic sensor unit 2.

Each electromagnet 62 is mounted in a corresponding one of the electromagnet mounting holes on the calibration support body 61 and uniformly distributed around the ultrasound probe 1 including the magnetic sensor unit 2, and a magnetic field generated by the electromagnet 62 can be acquired by the magnetic sensor unit 2. The number of electromagnets 62 should be not less than 4 and all be of the same type or have the same structure and dimensions so that when the same magnitude of current is input, all electromagnets 62 have the same or approximately the same magnetic coercivity, producing the same or approximately the same magnetic field.

The N-shaped lines 63 are installed in N-shaped line installation holes on the calibration support main body 61 and intersect with the imaging plane of the ultrasonic probe 1, as shown in fig. 7, one N-shaped line 63 forms a plurality of N-shaped structures through multiple direction changing, the starting point, the ending point and the direction changing point of one N-shaped line 63 are called as "inflection points", wherein the parts between adjacent inflection points are connected by straight lines, 3 straight lines between the 4 continuous inflection points form an N-shaped structure, two straight lines exist in the N-shaped structure in parallel relationship, the two straight lines are called as "side lines", the other straight line is called as "oblique line", and one straight line exists in each N-shaped structure and is perpendicular to the imaging plane of the ultrasonic probe 1. The material used for the N-shaped line 63 should have a large difference from the muscle density of the human body, such as nylon, so that the N-shaped line 63 has a good ultrasonic imaging effect.

The sound guiding medium 64 is filled in the sound guiding medium accommodating cavity of the calibration support main body 61, which is positioned under the ultrasonic probe 1, so that the sound guiding medium 64 exists in the imaging range of the ultrasonic probe 1, the N-shaped line 63 completely passes through the sound guiding medium 64, and the ultrasonic probe 1 can image the cross section of the N-shaped line 63. The density of the material used for the sound guiding medium 64 is similar to that of human muscle, such as water, agar, etc.

The calculation module is configured in the operation unit 4, and after the ultrasonic probe 1 comprising the magnetic sensor unit 2 is placed in the ultrasonic probe placing hole 611, the calculation module controls all the electromagnets 62 to be turned on and off one by one, only one electromagnet 62 is turned on each time, and the magnetic field vector of each time is recorded; according to the magnetic field vector of each time, calculating the relative pose relation between each magnetic sensor in the magnetic sensor unit 2 and the calibration support main body 61 based on a least square method, and calculating the relative pose relation between each magnetic sensor in the magnetic sensor unit; acquiring an ultrasonic image by using the ultrasonic probe 1, wherein the ultrasonic image comprises an acoustic guiding medium 64 and an N-shaped line 63 cross section; selecting the central position of the section of the N-shaped line 63 from the acquired ultrasonic image; based on the center position of the cross section of the N-shaped line 63 and the relative pose relationship between each magnetic sensor in the magnetic sensor unit 2 and the calibration support main body 61, the relative pose relationship between the ultrasonic probe 1 and the calibration support main body 61 is calculated, and the relative pose relationship between the ultrasonic probe 1 and the magnetic sensor unit 2 is calculated.

The second aspect of the present disclosure provides an interventional magnetic navigation method under ultrasound guidance, which is executed in the arithmetic unit 4, and as seen in fig. 8, fig. 8 is a flowchart of an embodiment of the interventional magnetic navigation method under ultrasound guidance provided in the second aspect of the present disclosure, including steps S801 to S807, wherein:

in step S801, the ultrasound probe 1 and the magnetic sensor unit 2 are calibrated to obtain a relative pose relationship between each magnetic sensor in the magnetic sensor unit 2, and a relative pose relationship between the magnetic sensor unit 2 and the ultrasound probe 1, which are used in subsequent positioning calculation of the magnetic interventional needle 3. As seen in fig. 9, fig. 9 is a flowchart of an embodiment of step S801 in fig. 8 provided in the second aspect of the present disclosure, including steps S901 to S907, where:

in step S901 and step S902, each magnetic sensor in the magnetic sensor unit 2 is respectively corrected, because the magnetic sensor has errors in the manufacturing process and electromagnetic interference exists in surrounding circuits, so that the magnetic field vector result directly measured by the magnetic sensor is different from the actual magnetic field vector, a correction coefficient is required to be obtained through correction, and the actual magnetic field vector is calculated by using the correction coefficient and the measured value of the magnetic sensor. According to the description in patent US7275008B2, when the magnetic sensor unit performs a rotational motion in an open environment, the collected magnetic field vector is recorded in the form of three-dimensional coordinates, the recorded result should show an oblique ellipsoid distribution deviating from the origin, and since the magnitude of the magnetic field in the open environment remains unchanged, the actual magnetic field vector distribution should be a sphere with the origin at which the center of the circle is located.

In step S901, the magnetic sensor unit 2 performs random movement in an open environment, in which the magnetic sensor unit 2 should be oriented in as many directions as possible, and the magnetic field vector measurement value of each of the magnetic sensors in the magnetic sensor unit 2 during the movement is recorded.

In step S902, correction coefficients of the respective magnetic sensors are calculated from the magnetic field vector measurement values. The correction coefficient of the magnetic sensor comprises a bias vector V and a scaling matrix W, the magnetic field vector measurement value is regarded as a three-dimensional coordinate, ellipsoid fitting is carried out on the three-dimensional coordinate, wherein the central coordinate of the ellipsoid obtained by fitting is the bias vector V of the magnetic sensor, the coefficient matrix of the ellipsoid transformed into a sphere is the scaling matrix W of the magnetic sensor, and the magnetic field vector measurement value of each magnetic sensor is obtained by the calculation of the magnetic field vector measurement value of each magnetic sensorThe respective true magnetic field vectors B can be obtained by calculation, and the calculation formula is as follows:

in step S903, the ultrasonic probe 1 including the magnetic sensor unit 2 is placed in the calibration support body 61 of the calibration support 6. During calibration, the ultrasound probe 1, the magnetic sensor unit 2 and the calibration support 6 should remain stationary.

In step S904, all electromagnets 62 are turned on and off one by one. Wherein, When the electromagnets 62 are turned on, it is sufficient that at most one electromagnet 62 is turned on at a time, and each electromagnet 62 is turned on. Further, the magnitude of the current that is turned on when each electromagnet 62 is turned on should be kept uniform, and the reverse current should be turned on to eliminate remanence when the electromagnets 62 are turned off. Let i be a positive integer not greater than the number of magnetic sensors, j be a positive integer not greater than the number of electromagnets 62, and when the jth electromagnet 62 is turned on, the magnetic field vector obtained by the ith magnetic sensor in the magnetic sensor unit 2 is corrected to be ^Ti B _ij And marks the coordinate of the center of the jth electromagnet 62 under the coordinate system of the calibration support main body 61 as ^w P _j The vector direction of the central magnetic field of the jth electromagnet 62 is under the coordinate system of the calibration support main body 61 ^w H _j . When all electromagnets 62 are in the off state, the magnetic field vector acquired by the ith magnetic sensor in the magnetic sensor unit 2 at this time is corrected to be ^Ti B _i0 . Wherein the coordinate system of the calibration support body 61 is { w }, and the coordinate system of the ith magnetic sensor is { T } _i }。

In step S905, the pose of each magnetic sensor in the magnetic sensor unit 2 is calculated from the data acquired in step S904. The magnetic sensor generally uses three measurement components to measure the magnetic field in three directions, for example, the magneto-impedance sensor uses three magneto-sensitive bridges to measure, and the hall sensor uses three hall elements to measure, so the pose of the magnetic sensor should include the coordinates of the three measurement components and the pose of the magnetic sensor coordinates. For the ith magnetic sensor, under the coordinate system of the calibration support body 61, the coordinate of the measurement component for measuring the X-axis magnetic field component is as follows ^w P _ix The coordinates of the measuring components for measuring the Y-axis magnetic field component are as follows ^w P _iy The coordinates of the measuring components for measuring the Z-axis magnetic field component are as follows ^w P _iz And a rotation matrix of the ith magnetic sensor coordinate system with respect to the calibration support body 61 coordinate systemIn the process of calculating the pose of the magnetic sensor, an electromagnet magnetic field model is needed to be used and is then usedSimplified into a current loop magnetic dipole model, namely, the ith magnetic sensor measures and obtains the theoretical value of a magnetic field vector generated by the jth electromagnet +.>The calculation formula of (2) is as follows:

wherein M is _e Is the coercivity coefficient of electromagnet 62, (-) _x Representing the X-axis component of the vector, (. Cndot.) _y Representing the Y-axis component of the vector, (. Cndot.) _z Representing the Z-axis component of the vector, |·| represents the two norms of the vector.

The coercivity coefficient M of the electromagnet can be calculated by least squares methods, e.g. quantum particle swarm optimization (Quantum Particle Swarm Optimization, QPSO) _e Pose parameters of ith magnetic sensor ^w P _ix 、 ^w P _iy 、 ^w P _iz 、The specific calculation formula is as follows:

since the above calculation result is the pose of the magnetic sensor in the coordinate system of the calibration support body 61, it is necessary to convert it into the pose of the magnetic sensor unit 2 in the coordinate system. Assuming that the origin of the coordinate system of the magnetic sensor unit 2 coincides with the bridge of the 1 st magnetic sensor for measuring the X-axis magnetic field component, the direction is the same as the direction of the 1 st magnetic sensor coordinate system, the coordinate system of the magnetic sensor unit 2 is { T }, and the bridge of the ith magnetic sensor for measuring the X-axis magnetic field component under the coordinate system of the magnetic sensor unit 2 is taken as the coordinate ^T P _ix Bridge for measuring Y-axis magnetic field component as coordinates ^T P _iy Bridge for measuring Z-axis magnetic field component as coordinates ^T P _iz And ith magnetic sensorRotation matrix of coordinate system of magnetic sensor unit 2 relative to coordinate system of magnetic sensor unitThe calculation formula of (2) is as follows:

after the pose of each magnetic sensor in the magnetic sensor unit 2 is obtained, it is also necessary to obtain the relative pose relationship between the magnetic sensor unit 2 and the ultrasonic probe 1, which will be described in detail in step S908.

In step S906, an ultrasonic image including the acoustic medium 64 and the N-shaped line 63 cross section is acquired by the ultrasonic probe 1.

In step S907, the cross-sectional center position of the N-type line 63 is selected from the ultrasonic image acquired in step S906. In the ultrasound image, the N-shaped line 63 is shown in cross section as a white dot, and the pixel at the center of the white dot is determined by a manual or automatic selection method. Let k be a positive integer not greater than the number of selected pixels, the pixel coordinates of the kth selected pixel be (x _k ,y _k )。

In step S908, a relative pose relationship between the magnetic sensor unit 2 and the ultrasound probe 1 is calculated, in which the ultrasound probe 1 coordinate system and the ultrasound image coordinate system { I } are set to coincide. According to the imaging parameters of the ultrasonic probe 1, the actual length of the side length of the pixel of the ultrasonic image can be obtained to be s, and then the coordinate of the kth selected pixel under the coordinate system of the ultrasonic probe 1 ^I P _pk ＝[sx _k sy _k 0] ^T . As can be seen from fig. 10, in one N-type structure of the N-type line 63, the intersection point of the ultrasonic image and the N-type structure edge is referred to as "edge point", the intersection point of the ultrasonic image and the N-type structure oblique line is referred to as "oblique point", and the distances between the oblique point and the two edge points are set to be d respectively ₁ And d ₂ The two side lines and the inclined line divide the inclined line into two sections, and the lengths of the two sections are respectively set as l ₁ And l ₂ Wherein the edge points with the same serial numbers and the oblique line segments are positioned on the same side of the oblique point, the L can be obtained according to the parallel relationship of the edge lines ₁ /l ₂ ＝d ₁ /d ₂ Wherein d is ₁ And d ₂ The value of (2) can be calculated by the coordinates of the above-mentioned pixels in the coordinate system of the ultrasonic probe 1. Since the dimensions of the calibrated support body 61 and the N-line 63 are known, l can be calculated from the dimensional relationships described above ₁ And l ₂ Thereby calculating the coordinates of the center of the section of the N-shaped line 63 corresponding to the kth selected pixel in the coordinate system of the calibration support main body 61 ^w P _pk The origin coordinates of the coordinate system of the ultrasonic probe 1 under the coordinate system of the calibration support body 61 are calculated by using a point cloud precision registration method (Iterative Closest Point, ICP) ^w P _I And a calibration support body 61 coordinate system and ultrasonic probe 1 coordinate system transformation rotation matrix _I ^w R, the calculation formula is:

the relative pose relationship between the ultrasonic probe 1 and the magnetic sensor unit 2 can be calculated, and the rotation matrix can be obtained Translation vector->So far, the calibration work for the ultrasonic probe 1 and the magnetic sensor unit 2 is completed entirely.

In step S802, the ambient magnetic field magnitude is measured and calculated. Before each navigation, the magnetic sensor unit 2 needs to be placed in a use environment, and the magnetic interventional needle 3 should be far away from the magnetic sensor unit 2, so that the magnetic sensor unit 2 cannot measure the magnetic field generated by the magnetic interventional needle 3, that is, the magnetic field generated by the magnetic interventional needle 3 is located outside the detection range of the magnetic sensor unit 2, at this time, the magnetic sensor unit 2 is used for acquiring the magnetic field vector at this time, and the magnetic field vector acquired by the ith magnetic sensor in the magnetic sensor unit 2 is corrected to be ^Ti B _iE (measurement of magnetic field vector obtained by the magnetic sensor using the correction coefficient determined in step S902)Value is obtained ^Ti B _iE ) The ambient magnetic field magnitude E is then:

where N is the number of magnetic sensors in the magnetic sensor unit 2.

Steps S803 to S807 are execution steps during navigation, each of which is executed in turn during navigation.

In step S803, the magnetic sensor unit 2 acquires a magnetic field vector, and the magnetic field vector acquired by the ith magnetic sensor in the magnetic sensor unit 2 is corrected as follows ^Ti B _i 。

In step S804, the ambient magnetic field estimation direction is calculated and the midpoint position of the magnetic interventional needle 3 is estimated based on the magnetic gradient tensor method, and as seen in fig. 11, fig. 11 is a flowchart of an embodiment of step S804 in fig. 8 provided in the present disclosure, including steps S1101 to S1103, wherein:

In step S1101, an average ambient magnetic field vector and an ambient magnetic field estimation direction are calculated from the magnetic field vector acquired in step S803. Since the magnitude of the magnetic field generated by the magnetic interventional needle 3 is much smaller than the magnitude of the ambient magnetic field, the ambient magnetic field vector is considered to be approximately equal to the average value of the magnetic field vectors acquired by the magnetic sensor unit 2, and the average ambient magnetic field vector is taken asThe calculation formula is as follows: />

Based on the average ambient magnetic field vectorCalculating the estimated direction of the environmental magnetic field +.>

In step S1102, a magnetic gradient tensor and an average magnetic field vector at the center of each magnetic sensor array are calculated from the magnetic field vector acquired by the magnetic sensor unit 2 and the relative pose relationship of the magnetic sensors in the magnetic sensor unit 2. FIG. 3 is a diagram showing an embodiment of a magnetic sensor array, wherein the distance d between the magnetic sensors in the magnetic sensor array in the X-direction and the Y-direction can be calculated based on the position coordinates of the magnetic sensors in the magnetic sensor unit 2 calculated in step S801 _x And d _y Corrected magnetic field vectors obtained from magnetic sensors s1, s2, s3, s4 in a magnetic sensor array ^T B _s1 、 ^T B _s2 、 ^T B _s3 、 ^T B _s4 The average magnetic field vector in the center of the magnetic sensor array can be calculated ^T B _O Magnetic gradient tensor ^T G _O The calculation formula is as follows:

^T B _O ＝( ^T B _s1 + ^T B _s2 + ^T B _s3 + ^T B _s4 )/4

In this embodiment of the magnetic sensor array, the distribution direction of the magnetic sensor array is the same as the X-axis and Y-axis directions of the coordinate system of the magnetic sensor unit 2, and if the distribution direction is other, additional coordinate conversion is required, which is not described herein.

In step S1103, the average magnetic field vector of the center of the magnetic sensor array calculated in step S1102 is used ^T B _O And magnetic gradient tensor ^T G _O The midpoint position of the magnetic interventional needle 3 is calculated. In one embodiment of the present application, the number of the magnetic sensor arrays in the magnetic sensor unit 2 is set to N _r M and N are not more than N _r The average magnetic field vector and magnetic gradient tensor at the center of the mth magnetic sensor array and the nth magnetic sensor array are respectively ^T B _Om 、 ^T B _On And ^T G _Om 、 ^T G _On the position coordinates are respectively ^T P _Om 、 ^T P _On The midpoint position of the magnetic interventional needle 3 can be calculated as ^T P _M ：

In step S805, the midpoint position of the magnetic interventional needle 3 is set ^T P _M And the direction of the ambient magnetic fieldAs initial values, the needle tip position, the needle tail position, the axial rotation angle, the magnetic coercivity, and the ambient magnetic field direction of the magnetic interventional needle 3 are calculated based on the least square method. As seen in fig. 12, the positions of the needle tip and the needle tail of the magnetic interventional needle 3 are defined as projection positions of the needle tip and the needle tail of the magnetic interventional needle 3 on the central axis of the magnetic interventional needle 3, respectively, the distance between the needle tip and the needle tail is equal to the longest distance in the axial direction of the magnetic interventional needle 3, and the axial rotation angle is defined as the angle between the connecting line of the needle tip position and the needle tip and the shortest distance direction from the origin of the coordinate system of the magnetic sensor unit 2 to the axis of the magnetic interventional needle 3. Using least square method to calculate a mathematical model requiring magnetic intervention needle 3 to generate magnetic field, the present disclosure provides a magnetic field model of magnetic intervention needle when needle tip position coordinates of magnetic intervention needle 3 are ^T P _p The position coordinates of the needle tail are ^T P _n An axial rotation angle of alpha and a magnetic coercivity of M _n Radius r, needle tip length l _t The direction vector of the magnetic interventional needle 3 ^T n _n And tip coordinates of the needle tip ^T P _t The method is calculated according to the following formula:

^T n _n ＝( ^T P _p - ^T P _n )/|| ^T P _p - ^T P _n ||

^T P _t ＝ ^T P _p +r[cosα( ^T P _p × ^T n _n × ^T n _n )+sinα ^T n _n ×( ^T P _p × ^T n _n × ^T n _n )]/|| ^T P _p ||

set magnetic interventional needle 3 at coordinates ^T P _r The magnetic field vector generated is ^T B _r The calculation formula is as follows:

where θ is an intermediate variable, the physical meaning of which can be understood as the angle of rotation around the axis of the magnetic interventional needle 3 in the integrating path.

It can be understood that, the magnetic field model of the magnetic intervention needle provided by the embodiment of the disclosure considers that magnetic charges are distributed on the needle tip and the needle tail surface according to the appearance of the magnetic intervention needle, and compared with other existing magnetic intervention needle models, the magnetic field model of the magnetic intervention needle provided by the embodiment of the disclosure retains the shape characteristics of the needle tip and the diameter characteristics of the magnetic intervention needle, so that the calculated theoretical magnetic field distribution is closer to the magnetic field distribution actually generated by the magnetic intervention needle, and particularly the phenomenon of sharp magnetic field enhancement is also considered. The magnetic interventional needle magnetic field model is used for the subsequent magnetic interventional needle positioning calculation, so that fitting errors caused by different magnetic field models and actual magnetic field distribution can be reduced, and the positioning accuracy of the magnetic interventional needle is improved.

From the magnetic needle magnetic field model and the positions of the magnetic sensors in the magnetic sensor unit 2 calculated in step S801, the magnetic field vector generated by the magnetic interventional needle 3 at the ith magnetic sensor position in the magnetic sensor unit 2 can be calculated as(theoretical value calculated by the magnetic field model of the magnetic interventional needle) the needle tip position, needle tail position, axial rotation angle and magnetic coercivity of the magnetic interventional needle 3, and the ambient magnetic field direction can be calculated based on the least square methodThe formula is:

wherein D is the magnetic declination of the environment magnetic field, and I is the inclination angle of the horizontal plane of the environment magnetic field.

The least square method commonly used optimization algorithm comprises methods such as a Levenberg-Marquardt algorithm, and the like, wherein most of the methods need to estimate the approximate numerical value of the quantity to be solved in order to avoid the divergence of the result or the calculation convergence to a local solution, and the invention adopts the calculated result in the step S804 as a solution initial value, namely the midpoint position of the magnetic interventional needle 3 ^T P _M As initial values of needle tip position and needle tail position, the ambient magnetic field estimates the directionAs the initial value of the environmental magnetic field, the initial values of the axial rotation angle and the magnetic coercivity can be set at will because they have little influence on the result.

In step S806, an ultrasound image is acquired in real time using the ultrasound probe 1.

In step S807, the needle tip position and the needle tail position in the ultrasonic image coordinate system are calculated from the needle tip position and the needle tail position of the magnetic interventional needle 3 obtained in step S805 and the relative pose relationship of the magnetic sensor unit 2 and the ultrasonic probe 1 obtained in step S801, and an ultrasonic image containing magnetic interventional needle pose information is generated. Since the ultrasonic image coordinate system and the ultrasonic probe 1 coordinate system are coincident, the needle tip position and the needle tail position of the magnetic interventional needle 3 under the ultrasonic image coordinate system are respectivelyConverted into pixel coordinates respectively (the scale of the scale is ^I P _p ) _x /s,( ^I P _p ) _y /s)、(( ^I P _n ) _x /s,( ^I P _n ) _y /s). After the needle tip position and the needle tail position of the magnetic interventional needle 3 under the ultrasonic image coordinate system are calculated, the ultrasonic image can be redrawn, such as in the ultrasonic imageDrawing a straight line passing through the two points of the needle point position and the needle tail position to provide pose information of the magnetic interventional needle 3, generating an ultrasonic image containing the pose information of the magnetic interventional needle, and displaying the ultrasonic image on the display device 5.

The ultrasonic probe is used for acquiring an ultrasonic image, the magnetic sensor unit is used for acquiring an environment magnetic field vector and a magnetic field generated by a magnetic intervention needle, the ultrasonic image and the magnetic field vector are sent to the operation unit to calculate the pose of the magnetic intervention needle and generate an ultrasonic image containing pose information of the magnetic intervention needle, the display device is used for displaying the ultrasonic image containing pose information of the magnetic intervention needle, and the calibration unit is used for calibrating parameters of the ultrasonic probe and the magnetic sensor unit. In the method, firstly, parameters of an ultrasonic probe and a magnetic sensor unit are calibrated and calculated by using a calibration unit provided by the disclosure, the magnitude of an environmental magnetic field is obtained before navigation is started, a magnetic field vector is obtained in real time after navigation is started, the estimated direction of the environmental magnetic field is calculated, the midpoint position of a magnetic interventional needle is estimated based on a magnetic gradient tensor method, the midpoint position of the magnetic interventional needle is taken as an initial value, the needle point position, the needle tail position, the axial rotation angle, the magnetic coercivity and the direction of the environmental magnetic field of the magnetic interventional needle are calculated based on a least square method, a real-time ultrasonic image is finally obtained, and an ultrasonic image containing pose information of the magnetic interventional needle is calculated and drawn according to a calibration result.

According to the technical scheme, the magnetic interventional needle is magnetized to generate a constant magnetic field, the magnetic sensor unit is arranged on the ultrasonic probe, and based on magnetic gradient tensor, a magnetic field model of the magnetic interventional needle and other theoretical models, accurate and rapid positioning of the magnetic interventional needle is achieved, accurate interventional needle pose information is provided for doctors, interventional difficulty is effectively reduced, and interventional accuracy and success rate are improved. The used magnetic sensor unit is small in size and low in price, can be built in the ultrasonic probe, realizes the navigation function, ensures the convenience of the equipment device, and does not need to change the operation habit of doctors. The calibration unit provided by the disclosure can accurately calibrate and calculate the internal parameters of the magnetic sensor unit and the relative pose between the magnetic sensor unit and the ultrasonic probe, further improve the navigation positioning precision, and realize the full-flow automation of the calibration process.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

While examples of the present invention have been shown and described above, it will be understood that the above examples are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations may be made to the above examples by one of ordinary skill in the art within the scope of the invention.

Claims

1. An ultrasound guided interventional magnetic navigation system, comprising:

the ultrasonic probe is used for acquiring an ultrasonic image;

2. The interventional magnetic navigation system of claim 1, wherein the parameters of the magnetic sensor unit include correction coefficients for each magnetic sensor within the magnetic sensor unit and relative pose relationships between each magnetic sensor, and wherein the parameters of the magnetic sensor unit and the ultrasound probe include relative pose relationships between the magnetic sensor unit and the ultrasound probe.

3. The interventional magnetic navigation system of claim 1, wherein the mathematical expression of the magnetic field model of the magnetic interventional needle is:

wherein, ^T B _r in coordinates for magnetic interventional needle ^T P _r A magnetic field vector generated thereat; ^T P _p and ^T P _n the needle point position coordinates and the needle tail position coordinates of the magnetic interventional needle are defined as projection positions of the needle point and the needle tail of the magnetic interventional needle on the axis of the magnetic interventional needle respectively; ^T P _t tip coordinates for magnetic interventional needlesThe method comprises the steps of carrying out a first treatment on the surface of the Alpha is the axial rotation angle of the magnetic interventional needle, and is defined as an included angle between the connecting line of the needle tip position and the needle tip and the shortest distance direction from the origin of the coordinate system of the magnetic sensor unit to the axis of the magnetic interventional needle; m is M _n Magnetic coercivity for a magnetic interventional needle; r and l _t The radius and the needle tip length of the magnetic interventional needle are respectively; θ is the angle of rotation about the axis of the magnetic interventional needle in the integration path.

4. The interventional magnetic navigation system according to claim 1, wherein the computing unit estimates the magnetic interventional needle midpoint position based on a magnetic gradient tensor method, comprising:

5. The interventional magnetic navigation system according to claim 4, wherein the obtaining the estimated direction of the environmental magnetic field according to the magnetic field vector obtained by the magnetic sensor unit and the relative pose relationship among the magnetic sensors in the magnetic sensor unit, and estimating the midpoint position of the magnetic interventional needle based on the magnetic gradient tensor method specifically comprises:

Taking the average value of magnetic field vectors acquired by magnetic sensors in the magnetic sensor unit as an average ambient magnetic field vectorAccording to the mean ambient magnetic field vector +.>Calculating the estimated direction of the environmental magnetic field +.>

6. The interventional magnetic navigation system according to any one of claims 1-5, further comprising a calibration unit for calibrating parameters of the magnetic sensor unit and the ultrasound probe before navigating an operational state, the calibration unit comprising:

7. The interventional magnetic navigation system of claim 6, wherein the number of electromagnets is not less than 4 and the electromagnets are capable of generating the same or approximately the same magnetic field.

8. The interventional magnetic navigation system of claim 6, wherein,

9. A navigation method of an interventional magnetic navigation system according to any one of claims 1 to 5, comprising the steps of:

step 5: acquiring an ultrasonic image by using the ultrasonic probe;

10. The navigation method of claim 9, further comprising calibrating parameters of the magnetic sensor unit and the ultrasound probe with a calibration unit prior to step 1, the calibration unit comprising:

the N-shaped lines are arranged in the N-shaped line mounting holes and are intersected with the imaging plane of the ultrasonic probe, the N-shaped lines comprise a plurality of N-shaped structures, two straight lines in the N-shaped structures are in parallel relation, and one straight line is perpendicular to the imaging plane of the ultrasonic probe;

The computing module is used for computing the relative pose relation among the magnetic sensors in the magnetic sensor unit and the relative pose relation between the magnetic sensor unit and the ultrasonic probe;