In-vivo positioning mapping system based on RFID

Abstract

The application relates to the field of medical equipment, in particular to an in-vivo positioning and mapping system based on RFID, which comprises an antenna, an RFID positioning target object, an RFID reference tag array, an RFID reader and a data processing device. In the use process, all the antennas receive the radio frequency signals fed back by the RFID positioning target object and the RFID reference tags in real time, the ranging error of the antenna is calculated by taking the RFID reference tags on the RFID reference tag array as the reference, the nearest RFID reference tag is determined by using the feedback signal of the RFID positioning target object, and the coordinates of the RFID positioning target object are calculated by the coordinates of the RFID reference tag and the ranging error. The method can apply the positioning technology based on the RFID radio frequency identification to the in-vivo positioning by using fewer radio frequency devices, can not affect the normal operation of other devices in the operation, and can eliminate the error and ensure the positioning precision.

Description

Technical Field

[0001] This invention relates to the field of medical devices, and more specifically to an RFID-based in vivo positioning and mapping system. Background Technology

[0002] Medical navigation and positioning systems involve the tracking and positioning of targets in three-dimensional space. Target devices include catheters, guidewires, guides (sheaths), probes, biopsy tools, etc. Application areas include pulmonary bronchial positioning and navigation, cardiac interventional therapy navigation, renal artery ablation navigation, endoscopic navigation, etc. Recently, minimally invasive interventional surgery has gradually become an effective treatment method due to its advantages such as less trauma, less pain, and faster recovery, and has gained widespread recognition and use. Positioning and mapping technology is the most core part of this, and its role is to achieve real-time positioning during surgery without CT, establish a three-dimensional model, and accurately locate lesion points.

[0003] Currently, RFID (Radio Frequency Identification) technology is commonly used in the medical field for surgical instrument management, sample data management, equipment location tracking, and equipment usage status tracking, with very few applications involving the human body during surgery. For example, patent CN101598792A discloses a high-precision three-dimensional positioning device based on RFID within a small spatial area, applied for indoor positioning. This device includes multiple circuits and modules such as RFID tag components and a reader antenna array, which are attached to... Figure 4 As indicated in the corresponding text of the instruction manual, the object to be located will be placed within a three-dimensional antenna array composed of numerous antennas. However, in the medical field, on the one hand, due to the various instruments and equipment that may be used during surgery, the application of RFID-based positioning technology inside the human body during surgery is extremely difficult in order to avoid affecting the normal operation of other equipment. On the other hand, the medical field has high requirements for the accuracy of intra-body positioning, and the human body absorbs radio frequency signals, which increases the difficulty of accurate RFID positioning inside the human body. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems in the prior art that it is difficult to apply RFID positioning to the medical field for in vivo positioning and that positioning is difficult, and to provide an RFID-based in vivo positioning and mapping system.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] An RFID-based in-vivo positioning and mapping system includes an antenna, an RFID positioning target, an RFID reference tag array, an RFID reader, and a data processing device.

[0007] In the RFID reference tag array, each RFID reference tag is used to receive an excitation signal from the antenna and send a first feedback signal to the antenna;

[0008] The RFID positioning target is used to receive excitation signals and send a second feedback signal to the antenna;

[0009] The RFID reader is used to send an excitation signal through the antenna and receive a first feedback signal and a second feedback signal, and transmit the first feedback signal and the second feedback signal to the data processing device.

[0010] The data processing device is used to calculate the ranging error of the antenna based on the first feedback signal and the actual position of the RFID reference tag array, select an RFID reference tag based on the second feedback signal, and calculate the coordinates of the RFID positioning target using the coordinates of the selected RFID reference tag combined with the ranging error.

[0011] Preferably, the RFID positioning target is a biopsy tool, radiofrequency ablation catheter, pulse therapy catheter, or ultrasound catheter equipped with a micro RFID tag.

[0012] Preferably, the antenna includes at least three groups.

[0013] Preferably, multiple antennas are located on the same horizontal plane, and their orientation allows electromagnetic waves to pass through the patient's body and activate the RFID reference tag array.

[0014] Preferably, the RFID reference tag array is located within a regular polygon formed by each group of antennas as vertices.

[0015] Furthermore, the specific method for calculating the ranging error of the antenna based on the first feedback signal and the actual position of the RFID reference tag array includes:

[0016] S1, calculate the measurement distance d between the antenna and the RFID reference tag using the signal strength information contained in the first feedback signal. ij , where i represents the first feedback signal received by the i-th antenna, and j represents the j-th RFID reference tag;

[0017] S2, calculate the actual distance D between the i-th antenna and the j-th RFID reference tag. ij With the measured distance d ij The difference between err ij The difference err ij That is, the ranging error of the i-th antenna relative to the j-th RFID reference tag.

[0018] Preferably, when the number of antennas is greater than 3, the three antenna groups with the smallest error are selected as the dominant antenna groups.

[0019] Furthermore, the step of selecting the nearest RFID reference tag based on the second feedback signal specifically includes: calculating the measurement distance d between the antenna and the RFID reference tag using the signal strength information contained in the second feedback signal; and selecting the three nearest RFID reference tags based on the measurement distance d.

[0020] Preferably, the multiple RFID reference tags of the RFID reference tag array are distributed at equal intervals between each other on a horizontal reference tag array plate.

[0021] Furthermore, the coordinates (x, y, z) of the RFID-located target are calculated using the following formula:

[0022]

[0023] Where k represents the k-th of the three most recent RFID reference tags, x k ,y k This represents the x-axis and y-axis coordinates of the RFID reference tag, w k The weight represents the coordinates of the k-th RFID reference tag;

[0024]

[0025] z RSSI The z-axis coordinate is calculated using the signal strength information contained in the second feedback signal. phase The z-axis coordinate is calculated using the phase information contained in the second feedback signal.

[0026] Furthermore, the weight of the k-th RFID reference tag coordinates is calculated using the following formula:

[0027]

[0028] err k This is the error in measuring the distance to the k-th RFID reference tag among the three most recent RFID reference tags.

[0029] Preferably, the reference tag array plate has an arc-shaped surface that surrounds the RFID positioning target, and the multiple RFID reference tags of the RFID reference tag array are distributed on the arc-shaped surface at equal intervals between each other.

[0030] Preferably, the RFID-located target moves within the space enclosed by the arc-shaped surface.

[0031] Furthermore, the coordinates (x, y, z) of the RFID-located target are calculated using the following formula:

[0032]

[0033] Where k represents the k-th of the three most recent RFID reference tags, x k ,y k ,z k This represents the x-axis, y-axis, and z-axis coordinates of the RFID reference tag, w k This represents the weight of the coordinates of the k-th RFID reference tag.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. This invention constructs an in vivo positioning and mapping system comprising antennas, an RFID positioning target, an RFID reference tag array, an RFID reader, and a data processing device. During operation, all antennas receive radio frequency signals from the RFID positioning target and the RFID reference tags in real time. The ranging error of the antennas is first calculated using the RFID reference tags on the RFID reference tag array as a reference. The nearest RFID reference tag is determined using the feedback signal from the RFID positioning target. The coordinates of the RFID positioning target are then calculated using the coordinates of the RFID reference tag and the ranging error. This invention uses fewer radio frequency devices to apply RFID-based positioning technology to in vivo positioning, without affecting the normal operation of other equipment during surgery, and by combining the coordinates of the reference tags, errors can be eliminated to ensure positioning accuracy. Attached Figure Description

[0036] Figure 1 This is a system schematic diagram of an RFID-based in vivo positioning and mapping system.

[0037] Figure 2 This is a schematic diagram illustrating the implementation of Example 1.

[0038] Figure 3 This is the algorithm flowchart for Example 1.

[0039] Figure 4 This is a schematic diagram illustrating the implementation of Example 2.

[0040] Figure 5 This is the algorithm flowchart for Example 2.

[0041] Figure 6 This is a sample diagram of the RFID tag arrangement in the straight conduit in Embodiment 3 of the present invention.

[0042] Figure 7 This is a sample diagram of the arrangement of RFID tags in the annular conduit in Embodiment 3 of the present invention.

[0043] Reference numerals: 101-Location mapping workstation, 102-RFID positioning device, 201-Location mapping workstation, 202-Connection line between reader and location mapping workstation, 203-Reader, 204-Antenna connection line, 205-RFID reference tag array plate, 206-RFID reference tag, 207-Patient, 208-RFID positioning target, 209-Antenna, 401-Location mapping workstation, 402-Connection line between reader and location mapping workstation, 403-Reader, 404-Antenna connection line, 405-Reference tag array ring, 406-Reference tag, 407-Patient, 408-RFID positioning target, 409-Antenna, 410-Antenna bracket, 411-Description of the spatial coordinate system used, 412-RFID tag, 413-Location catheter. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0045] Example 1

[0046] The basic structure of the RFID-based in vivo positioning and mapping system of this invention is as follows: Figure 1 As shown, it includes a data processing device and an RFID positioning device. The data processing device is a positioning and mapping workstation 101, which is responsible for positioning signal processing and patient information management. The RFID positioning device 102 is responsible for collecting and analyzing the signals emitted by RFID positioning targets inside the human body.

[0047] RFID positioning targets include biopsy tools, radiofrequency ablation catheters, pulse therapy catheters, or ultrasound catheters equipped with miniature RFID tags.

[0048] Regarding the aforementioned RFID positioning device 102, this embodiment provides an implementation method for an RFID-based in-vivo positioning and mapping system, such as... Figure 2 As shown, this method uses a reference tag array to achieve positioning based on the received signal strength and phase information in RFID.

[0049] The positioning and mapping workstation 201 is responsible for storing and managing basic patient information and treatment data, processing radio frequency data, real-time intraoperative catheter positioning and tracking, and 3D modeling. The reader 203 is responsible for information transmission between the RFID tag and the positioning and mapping workstation 201. After being powered on, the reader transmits high-frequency electromagnetic waves through antenna 109, then collects the radio frequency signal of the RFID positioning target 208, analyzes it, and transmits the valid information to the positioning and mapping workstation 201. The RFID reference tag array 205 is parallel to the XOY plane (ground plane). During the operation, the patient 207 lies on the reference tag array 205. 206 represents the RFID reference tag. Multiple RFID reference tags are evenly spaced on the reference tag array 205 and are used to calculate the positioning data of the RFID positioning target 208 in the surgical environment. 207 represents the patient. The RFID positioning target 208 is inside the patient's body during the operation. It should be noted that, based on the principle of this invention, even when the patient's movement exceeds the reference tag array plate, the coordinates of the RFID positioning target can still be calculated. However, to ensure high accuracy, the RFID positioning target needs to be within the range of the RFID reference tag, or close to it. Preferably, in this embodiment, the horizontal movement range of the RFID positioning target does not exceed the size of the reference tag array plate 205. 209 represents an antenna. There are multiple antennas distributed around the patient, looking down at them. The antenna placement has the following requirements: firstly, the position should be relatively fixed or easy to measure, because the distance between the antenna and the RFID reference tag is known in subsequent calculations; secondly, the patient's body needs to be between the antenna and the RFID reference tag, and the antenna orientation should ensure that electromagnetic waves can pass through the patient's body and activate the RFID reference tag beneath the patient. This way, the electromagnetic waves, after being attenuated by the body, participate in the calculation of the RFID reference tag's positioning information. Measurement can be achieved at any distance between antennas without affecting the expression of the calculation formula, but the measurement error is minimized when the distance between adjacent antennas is equal. The even distribution of antennas ensures uniform signal distribution around the tag at various angles. For measurement accuracy, it is preferable that the distance between antennas be as equal as possible, forming a regular polygon, and that the reference tag array plate is positioned at the exact center of all antennas. In other words, antennas should be present at every angle of the tag, avoiding situations where antennas are densely packed at some angles and sparsely packed at others. 210 represents the antenna support, and 211 represents the spatial coordinate system used to describe the system.

[0050] The RFID reference tags are evenly distributed on the reference tag array plate 205 at equal intervals. This is because it is desirable to have a certain number of RFID reference tags to support position correction regardless of the location of the RFID positioning target. The distance between the RFID reference tags should not be too dense, to avoid the nearest reference tags being concentrated in the same direction of the RFID positioning target, thus affecting the test accuracy; nor should they be too sparse, ensuring that RFID reference tags can be found around the RFID positioning target to assist in positioning at any location. The distribution of the RFID reference tags does not affect the calculation formula.

[0051] The positioning algorithm process is as follows: Figure 3 As shown, it includes the following steps:

[0052] 301. Receives phase and signal strength information from the tags. Each antenna group can transmit radio frequency signals and receive feedback signals from electronic tags (including RFID reference tags and RFID positioning targets). After parsing, the phase and signal strength information contained in the feedback signals are transmitted to the positioning and measurement workstation.

[0053] 302. Modeling the positioning results of RFID reference tags. First, the signal strength information of the RFID reference tags is processed. Due to propagation path loss caused by the environment at the signal transmitter and receiver, the relationship between echo signal strength and transmission distance can be quantitatively expressed. Then, the distance between the antenna and the tag can be calculated based on the echo signal strength received by the antenna. In this system, the actual coordinates of the RFID reference tag are known. For each antenna group, the distance from the RFID reference tag to the antenna is known, and the echo signal strength received by the antenna from the reference tag is known. Therefore, the quantitative relationship between echo signal strength and distance can be established, meaning that a model for calculating distance using signal strength can be obtained for each antenna group.

[0054] 303. Evaluate the positioning model using reference tags. For each antenna group, the model established in 302 is used to calculate the distance to each RFID reference tag in the tag array. The difference between the calculated distance and the actual distance is evaluated, thereby assessing the ranging error of each antenna group. The evaluation results are a series of correspondences between distance and error, as shown in Table 1 below. Each column represents a set of correspondences; for example, the last column represents d. n The distance error is err n .

[0055] Table 1. Measurement distance and measurement error of a certain antenna to n RFID reference tags.

[0056]

[0057] 304. Select the dominant antenna group for RFID target location. Examine the distance measurements of each antenna group to the RFID target. Based on these distance measurements, refer to the distance-error relationship obtained in 303 to determine the error of each antenna group under its respective measurement results. Select the three antennas with the smallest errors; these three antenna groups are considered the dominant antenna groups in the current area. Based on the measured distance to the RFID target, find the three closest RFID reference tags, whose actual coordinates are (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3).

[0058] In this embodiment, only three antenna groups with the smallest errors were selected as the dominant antenna groups. However, the number of dominant antenna groups can be set as needed in the following way: if there are a total of m antennas participating in the positioning, then after sorting the antennas by their positioning errors from smallest to largest, the first i antennas are selected to calculate their weights, where i ≤ m and i ≥ 3. The antenna positioning error calculation method includes: after scanning, the distance d0 between the antenna and the RFID positioning target can be obtained, and the distances {d1, d2, d3…, d...} between the antenna and j reference tags can be obtained. j}, let d0 be an integer and {d1,d2,d3,…,d}. j By comparing the locations of several reference tags with the smallest differences, these reference tags can be considered to be in the vicinity of the RFID positioning target. The positioning error of these reference tags is then calculated as the positioning error of the antenna at that moment. A larger value for m means more antennas and more accurate positioning. However, after m increases to a certain extent, the rate of increase in accuracy will slow down or tend to plateau, and the entire system will become more redundant (more antenna devices, more computation), resulting in a smaller overall benefit. In this embodiment, m is set to 4 to cover all measurement angles with as few antennas as possible, while allowing for selection flexibility. Regarding the value of i, at least 3 antennas are needed to determine the position, without using more points. When the fourth antenna is added to the calculation, because the dominant antenna is selected based on error ranking, the positioning error of the fourth antenna will be larger than that of the first 3 antennas in the current state. Introducing the fourth antenna into the calculation will increase the average error, leading to less accurate positioning.

[0059] In this embodiment, the method for finding the three closest RFID reference tags based on the measured distance of the RFID positioning target includes: obtaining the distance d0 between any one of the antennas (in the dominant antenna group) and the tag to be measured, and the distances between the antenna and j reference tags {d1, d2, d3…, d…}. j}, let d0 be an integer and {d1,d2,d3,…,d}. jBy comparing the distances, the RFID reference tag with the smallest difference is considered the closest RFID reference tag. Correspondingly, the error corresponding to the distance with the smallest difference is the distance measurement error (err) of that RFID reference tag. k , where k is the sequence number of the RFID reference tag among the three nearest reference tags. With three antennas, each antenna finds one, resulting in a total of three nearest reference tags.

[0060] The weights are calculated using the distance error magnitude according to the following formula:

[0061]

[0062] Where w k The weight of the k-th RFID reference tag coordinates is represented by err. k The error (measurement error) in measuring the distance to the k-th reference label.

[0063] Use weight w k The x-axis and y-axis coordinates of the RFID positioning target are calculated from the coordinates of the RFID reference tag.

[0064]

[0065] Where w k The weight of the k-th RFID reference tag coordinates is represented by x. k ,y k This indicates the x-axis and y-axis coordinates of the RFID reference tag.

[0066] 305. The positioning information is supplemented by combining the received signal phase. The z-coordinate of the RFID positioning target is directly calculated using the received signal strength of the three dominant antenna groups. The second z-coordinate of the RFID positioning target can be calculated using the phase values ​​of the three dominant antenna groups. The final coordinate of the RFID positioning target is the average of these two z-coordinates.

[0067]

[0068] Where z RSSI The z-axis coordinate is calculated from the received signal strength. phase The z-axis coordinate is calculated from the phase of the received signal.

[0069] Example 2

[0070] This embodiment provides an implementation method for an RFID-based in vivo positioning and mapping system, such as... Figure 4 As shown, this method utilizes an arc-shaped reference tag array plate (referred to as a reference tag array ring in this embodiment) to achieve positioning based on the received signal strength in RFID. Figure 5 The algorithm flow corresponding to this embodiment.

[0071] The positioning and mapping workstation 401 is responsible for storing and managing basic patient information and treatment data, processing radio frequency data, real-time catheter positioning and tracking during surgery, and 3D modeling. The reader 403 is responsible for information transmission between the RFID tag and the positioning and mapping workstation 401. After being powered on, the reader transmits high-frequency electromagnetic waves through the antenna 409, then collects the radio frequency signal of the RFID positioning target 408, analyzes it, and transmits the valid information to the positioning and mapping workstation 401. During the surgery, the patient lies in the center of the reference tag array ring 405. Multiple reference tags 406 are evenly spaced on the reference tag array ring and are used to calculate the positioning data of the RFID positioning target 408 in the surgical environment. 408 is the RFID positioning target, which is inside the patient's body 407 during the surgery. It should be noted that, based on the principles of this invention, even when the patient's movement exceeds the reference tag array ring 405, the coordinates of the RFID positioning target can still be calculated. However, to ensure high accuracy, the RFID positioning target needs to be within the range of the RFID reference tags, or close to them. Preferably, in this embodiment, the movement range of the RFID positioning target does not exceed the area encircled by the reference tag array ring 405. Multiple antennas 409 are distributed around the patient 407. The antenna orientation must ensure that electromagnetic waves can pass through the patient's body and activate the reference tags around the patient. The antenna placement has the following requirements: firstly, the position should be relatively fixed or easy to measure, because the distance between the antenna and the RFID reference tag is known in subsequent calculations; secondly, the antenna orientation must ensure that electromagnetic waves can pass through the patient's body and activate the RFID reference tags on the reference tag array ring 405, so that the electromagnetic waves, after being lost through the body, participate in the calculation of the RFID reference tag's positioning information. Measurements can be performed at any distance between antennas without affecting the expression of the calculation formula. However, the measurement error is minimized when the distance between adjacent antennas is equal, and the even distribution of antennas ensures uniform signal distribution around the tag at all angles. For measurement accuracy, it is preferable that the distance between antennas be as equal as possible, forming a regular polygon, and that the reference tag array plate is positioned at the exact center of all antennas. In other words, antennas should be present at as many angles as possible around the tag, avoiding situations where antennas are densely packed at some angles and sparsely packed at others.

[0072] The RFID reference tags are evenly distributed on the reference tag array ring 405 with equal spacing. This is because it is desirable to have a certain number of RFID reference tags to support position correction regardless of the location of the RFID positioning target. The distance between the RFID reference tags should not be too dense, to avoid the nearest reference tags being concentrated in the same direction as the RFID positioning target, thus affecting the test accuracy; nor should they be too sparse, ensuring that RFID reference tags can be found around the RFID positioning target to assist in positioning at any location. The distribution of the RFID reference tags does not affect the calculation formula.

[0073] The flowchart of the localization algorithm in this embodiment is as follows: Figure 5 As shown, it includes the following steps:

[0074] 501. Obtain received signal strength information. Each antenna can transmit radio frequency signals and receive feedback signals from electronic tags (including RFID reference tags and RFID positioning targets). After parsing, the signal strength information contained in the feedback signals is transmitted to the positioning and measurement workstation.

[0075] 502. Modeling the positioning results of the reference tags. First, the signal strength information of the reference tags is processed. Due to propagation path loss caused by the environment at the signal transmitting and receiving ends, the relationship between echo signal strength and transmission distance can be quantitatively expressed. Then, the distance between the antenna and the tag is calculated based on the echo signal strength received by the antenna. In this system, the actual coordinates of the RFID reference tags are known. For each antenna, the distance from the RFID reference tag to the antenna is known, and the echo signal strength received by the antenna from the RFID reference tag is known. Therefore, the quantitative relationship between echo signal strength and distance can be established, meaning that a model of the distance between each antenna and each RFID reference tag can be calculated using the signal strength.

[0076] 503. Evaluating the Positioning Model Using RFID Reference Tags. For each antenna, the model established in 502 is used to calculate the distance to each RFID reference tag in the RFID reference tag array, and the difference between the calculated distance and the actual distance is evaluated. Based on this, the ranging error of each antenna can be evaluated, and the evaluation results are a series of correspondences between distance and error. As shown in the table below, each column represents a set of correspondences; for example, the last column represents d... n The distance error is err n .

[0077] Table 2. Measurement distance and measurement error of a certain antenna to n RFID reference tags.

[0078]

[0079] 504. Select the dominant antenna group for RFID target location. Examine the distance measurements of each antenna group to the RFID target. Based on these distance measurements, refer to the distance-error relationship obtained in 503 to determine the error of each antenna group under that antenna's measurement results. Select the three antennas with the smallest errors; these three antenna groups are considered the dominant antenna groups in the current area. Based on the measured distance to the RFID target, find the three closest reference tags with coordinates (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3).

[0080] In this embodiment, only three antenna groups with the smallest errors were selected as the dominant antenna groups. However, the number of dominant antenna groups can be set as needed in the following way: if there are a total of m antennas participating in the positioning, then after sorting the antenna positioning errors from smallest to largest, the first i antennas are selected to calculate the weights, where i≤m and i≥3. The antenna positioning error calculation method includes: after scanning, the distance d0 between the antenna and the RFID positioning target can be obtained, and the distances {d1,d2,d3…,d...} between the antenna and j reference tags can be obtained. j}, let d0 be an integer and {d1,d2,d3,…,d}. j By comparing the locations of several reference tags with the smallest differences, these reference tags can be considered to be in the vicinity of the RFID positioning target. The positioning error of these reference tags is then calculated as the positioning error of the antenna at that moment. A larger value for m means more antennas and more accurate positioning. However, after m increases to a certain extent, the rate of increase in accuracy will slow down or tend to plateau, and the entire system will become more redundant (more antenna devices, more computation), resulting in a smaller overall benefit. In this embodiment, m is set to 4 to cover all measurement angles with as few antennas as possible, while allowing for selection flexibility. Regarding the value of i, at least 3 antennas are needed to determine the position, without using more points. When the fourth antenna is added to the calculation, because the dominant antenna is selected based on error ranking, the positioning error of the fourth antenna will be larger than that of the first 3 antennas in the current state. Introducing the fourth antenna into the calculation will increase the average error, leading to less accurate positioning.

[0081] In this embodiment, the method for finding the three closest RFID reference tags based on the measured distance of the RFID positioning target includes: obtaining the distance d0 between any one of the antennas (in the dominant antenna group) and the tag to be tested, and the distances between the antenna and the j reference tags {d1, d2, d3…, d…} j}, let d0 be an integer and {d1,d2,d3,…,d}. jBy comparing the distances, the reference tag corresponding to the smallest difference is considered the closest RFID reference tag. Correspondingly, the error corresponding to the smallest difference distance is the distance measurement error (err) of that RFID reference tag. k Let k be the index of the RFID reference tag among the three closest reference tags. Three antennas are used, each finding one tag, resulting in three closest reference tags. The weights are calculated using the distance error magnitude according to the following formula:

[0082]

[0083] err k The error in measuring the distance to the k-th reference label.

[0084]

[0085] k represents the k-th of the three most recent RFID reference tags, x k ,y k ,z k This represents the x-axis, y-axis, and z-axis coordinates of the RFID reference tag, w k This represents the weight of the k-th RFID reference tag coordinates. The coordinates of the RFID-located target object are then obtained from this.

[0086] Example 3

[0087] Figure 6 and Figure 7 A sample diagram of RFID tag arrangement is provided when the target object for RFID positioning is a catheter. For positioning accuracy, the RFID tag arrangement should consider the following: RFID tags should be placed according to the needs of different clinical applications, and priority should be given to placing them in easily deformable positions on the catheter, which is more conducive to accurately describing the catheter's morphology.

[0088] Figure 6 This is an example diagram of the RFID tag arrangement in a straight conduit. 413 is a positioning conduit with multiple RFID tags 412 distributed on it.

[0089] Based on the same concept, an example diagram of RFID tag arrangement in a ring-shaped positioning conduit is also provided, such as... Figure 7 As shown, the gray disc is an RFID tag. Due to the use of RFID tags, the RFID tag can be located through radio frequency signals, thereby accurately describing the shape of the conduit and avoiding the errors of a single positioning method.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An RFID-based in vivo positioning and mapping system, characterized in that, Includes antennas, RFID positioning targets, RFID reference tag arrays, RFID readers, and data processing devices. In the RFID reference tag array, each RFID reference tag is used to receive an excitation signal from the antenna and send a first feedback signal to the antenna; The RFID positioning target is used to receive excitation signals and send a second feedback signal to the antenna; The RFID reader is used to send an excitation signal through the antenna and receive a first feedback signal and a second feedback signal, and transmit the first feedback signal and the second feedback signal to the data processing device. The data processing device is used to calculate the ranging error of the antenna based on the first feedback signal and the actual position of the RFID reference tag array, select an RFID reference tag based on the second feedback signal, and calculate the coordinates of the RFID positioning target using the coordinates of the selected RFID reference tag combined with the ranging error. The step of selecting RFID reference tags based on the second feedback signal specifically includes: calculating the measurement distance d between the antenna and the RFID positioning target using the signal strength information contained in the second feedback signal; and selecting the three closest RFID reference tags based on the measurement distance d. Calculate the coordinates of the RFID target object The following formula is used for calculation: Where k represents the k-th of the three most recent RFID reference tags, , This indicates the x-axis and y-axis coordinates of the RFID reference tag. The weight represents the coordinates of the k-th RFID reference tag; The z-axis coordinate is calculated using the signal strength information contained in the second feedback signal. The z-axis coordinate is calculated using the phase information contained in the second feedback signal; The weight of the k-th RFID reference tag coordinate is calculated using the following formula: The ranging error is the distance measurement error of the k-th RFID reference tag among the three most recent RFID reference tags.

2. The RFID-based in vivo positioning and mapping system as described in claim 1, characterized in that, The RFID positioning target is a biopsy tool, radiofrequency ablation catheter, pulse therapy catheter, or ultrasound catheter equipped with a micro RFID tag.

3. The RFID-based in vivo positioning and mapping system as described in claim 1, characterized in that, The antenna consists of at least three sets.

4. The RFID-based in vivo positioning and mapping system as described in claim 3, characterized in that, The antenna is oriented so that electromagnetic waves pass through the patient's body and can activate the RFID reference tag array.

5. The RFID-based in vivo positioning and mapping system as described in claim 1, characterized in that, The RFID reference tag array is located within a regular polygon formed by each group of antennas as vertices.

6. An RFID-based in vivo positioning and mapping system as described in any one of claims 1-5, characterized in that, The specific method for calculating the ranging error of the antenna based on the first feedback signal and the actual position of the RFID reference tag array includes: S1, calculate the measurement distance between the antenna and the RFID reference tag using the signal strength information contained in the first feedback signal. , where i represents the first feedback signal received by the i-th antenna, and j represents the j-th RFID reference tag; S2, calculate the actual distance Dij between the i-th antenna and the j-th RFID reference tag and the measured distance. The difference between The difference That is, the ranging error of the i-th antenna relative to the j-th RFID reference tag.

7. The RFID-based in vivo positioning and mapping system as described in claim 6, characterized in that, When the number of antennas is greater than 3, the three antenna groups with the smallest error are selected as the dominant antenna groups.

8. The RFID-based in vivo positioning and mapping system as described in claim 1, characterized in that, Multiple RFID reference tags in an RFID reference tag array are distributed at equal intervals on a horizontal reference tag array plate.

9. The RFID-based in vivo positioning and mapping system as described in claim 1, characterized in that, The system also includes a reference tag array plate, which has an arc-shaped surface that surrounds the RFID positioning target. Multiple RFID reference tags of the RFID reference tag array are distributed on the arc-shaped surface at equal intervals between each other.

10. The RFID-based in vivo positioning and mapping system as described in claim 9, characterized in that, The RFID-located target moves within the space enclosed by the curved surface.

11. The RFID-based in vivo positioning and mapping system as described in claim 10, characterized in that, Calculate the coordinates of the RFID target object The following formula is used for calculation: Where k represents the k-th of the three most recent RFID reference tags, This indicates the x-axis, y-axis, and z-axis coordinates of the RFID reference tag. This represents the weight of the coordinates of the k-th RFID reference tag.

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