CN102258371A

CN102258371A - Device and method for detecting foreign matters in skin on basis of hollow-core sensor

Info

Publication number: CN102258371A
Application number: CN2010105331089A
Authority: CN
Inventors: 尹武良; 王奔; 杨靖怡; 尹丽媛
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2010-11-05
Filing date: 2010-11-05
Publication date: 2011-11-30

Abstract

The invention belongs to the technical field of electromagnetic sensors, and relates to a detection device for tumors or foreign bodies in the skin based on a hollow sensor, including a hollow sensor, a signal generating unit, a signal acquisition unit, a power amplifier and a host computer. The hollow sensor It is an air-core coil, placed vertically above the skin to be tested at a certain distance, and the current excitation signal generating unit is controlled by the host computer to apply the excitation current signal to the air-core coil, and the phase of the applied excitation current signal is measured by the induction signal unit. Induced voltages that differ by 90 degrees. The invention also provides a detection method realized by using the detection device. The device and method of the invention are more practical and convenient, and are one of the most feasible detection tools for tumors or foreign objects in the skin.

Description

Device and method for foreign body detection in skin based on hollow sensor

技术领域 technical field

本发明属于电磁传感器技术领域，具体涉及一种皮肤内肿瘤或者异物探测装置及测量方法。The invention belongs to the technical field of electromagnetic sensors, and in particular relates to an intradermal tumor or foreign body detection device and a measurement method.

背景技术 Background technique

皮肤肿瘤是发生在皮肤的细胞增生性疾病，是一种常见病。发生于皮内或皮下组织的新生物，种类很多，临床上分良性肿瘤和恶性肿瘤。恶性肿瘤可以不断增殖，引起转移，威胁生命，称为皮肤癌。Skin tumor is a cell proliferative disease that occurs in the skin and is a common disease. There are many types of neoplasms that occur in the intradermal or subcutaneous tissue, clinically divided into benign tumors and malignant tumors. Malignant tumors can continue to proliferate, cause metastasis, and threaten life, which is called skin cancer.

皮肤内的异物，例如铅笔头、针头等等，不仅触碰时会有疼痛感，而且在皮肤内会有不良的反应。需要及早的发现，并且取出。Foreign objects in the skin, such as pencil heads, needles, etc., not only cause pain when touched, but also have adverse reactions in the skin. It needs to be detected and removed early.

目前，皮肤内肿瘤或者异物探测通常是使用皮肤检测仪。皮肤检测仪价格昂贵，体积稍大，并且需要接触皮肤进行检测。At present, the detection of tumors or foreign objects in the skin usually uses a skin detector. Skin detectors are expensive, slightly bulky, and need to touch the skin for detection.

发明内容 Contents of the invention

针对以上提到现有技术存在的缺陷和不足，本发明的目的提出一种利用电磁方法测量皮肤内肿瘤或异物的装置。本发明采用如下的技术方案：Aiming at the defects and deficiencies in the prior art mentioned above, the object of the present invention is to provide a device for measuring tumors or foreign objects in the skin by using electromagnetic methods. The present invention adopts following technical scheme:

一种基于空芯传感器的皮肤内肿瘤或异物的探测装置，包括空芯传感器、信号发生单元、信号采集单元、功率放大器和上位计算机，所述的空芯传感器为一个空芯线圈，竖直放置于待测皮肤一定距离的上方，由上位计算机控制电流激励信号发生单元向空芯线圈施加激励电流信号，并利用感应信号单元测量与所施加的激励电流信号相位相差90度的感应电压。A detection device for tumors or foreign bodies in the skin based on an air-core sensor, comprising an air-core sensor, a signal generating unit, a signal acquisition unit, a power amplifier and a host computer, the air-core sensor is an air-core coil, placed vertically Above the skin to be tested at a certain distance, the host computer controls the current excitation signal generating unit to apply the excitation current signal to the air-core coil, and uses the induction signal unit to measure the induced voltage with a phase difference of 90 degrees from the applied excitation current signal.

本发明的探测装置，所述的空芯线圈的直径可以为5-100mm。线圈的绕线匝数介于1-1000之间；绕线的直径在0.01mm-10mm之间。In the detection device of the present invention, the diameter of the air-core coil may be 5-100mm. The winding turns of the coil are between 1-1000; the diameter of the winding is between 0.01mm-10mm.

本发明同时提供一种采用上述装置实现的基于空芯传感器的皮肤内肿瘤或异物的探测方法，包括下列步骤：The present invention also provides a method for detecting tumors or foreign objects in the skin based on the hollow sensor implemented by the above-mentioned device, which includes the following steps:

(1)将皮肤内的组织分为n层，设定每一层的初始电导率σ_γ＝σ₁Lσ_n，(1) Divide the tissue in the skin into n layers, and set the initial conductivity σ _γ =σ ₁ Lσ _n of each layer,

(2)将空芯传感器置于离正常皮肤一定的高度，设线圈底部的高度l₁，线圈顶部的高度为l₂，线圈的匝数为N，内径和外径为r1和r2，设线圈的电感值为L₀，设对空芯传感器激励频率为ω₁Lω_m，根据下式计算在各个不同激励频率下的电感值变化量：(2) Place the air-core sensor at a certain height from the normal skin, let the height of the coil bottom be l ₁ , the height of the top of the coil be l ₂ , the number of turns of the coil be N, the inner and outer diameters be r1 and r2, set the coil The inductance value of the sensor is L ₀ , and the excitation frequency of the air-core sensor is ω ₁ Lω _m , and the inductance value variation at different excitation frequencies is calculated according to the following formula:

$ΔL (ω) = K {&Integral;}_{0}^{\infty} \frac{P^{2} (α)}{α^{6}} A (α) \frac{U_{12}}{U_{22}} dα,$ 其中， $Δ L (ω) = K {&Integral;}_{0}^{\infty} \frac{P^{2} (α)}{α^{6}} A (α) \frac{u_{12}}{u_{twenty two}} dα,$ in,

U＝H₂·H₁·H₀，U为2×2矩阵，U₁₂为该矩阵第一行第二列的数，U₂₂为矩阵第二行第二列的数，U=H ₂ ·H ₁ ·H ₀ , U is a 2×2 matrix, U ₁₂ is the number in the first row and second column of the matrix, U ₂₂ is the number in the second row and second column of the matrix,

${H h}_{k k} = = \frac{11}{22} [\begin{matrix} ((11 - - + + \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{(({α α}_{k k + + 11} - - {α α}_{k k})) \cdot \cdot {z z}_{k k}},, ((11 - - \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{(({α α}_{k k + + 11} + + {α α}_{k k})) \cdot &Center Dot; {z z}_{k k}} \\ ((11 - - \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{((- - {α α}_{k k + + 11} - - {α α}_{k k})) \cdot &Center Dot; {z z}_{k k}},, ((11 + + \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{(({α α}_{k k} - - {α α}_{k k + + 11})) \cdot \cdot {z z}_{k k}} \end{matrix}],,$

$P P ((α α)) = = {&Integral; &Integral;}_{{αr αr}_{11}}^{α α {r r}_{22}} x x {J J}_{11} ((x x)) dx dx,,$

$K K = = \frac{π π {μ μ}_{00} {N N}^{22}}{{(({l l}_{11} - - {l l}_{22}))}^{22} {(({r r}_{11} - - {r r}_{22}))}^{22}},,$

${α α}_{k k} = = \sqrt{{α α}^{22} + + jω jω {σ σ}_{k k} {μ μ}_{k k}},,$

式中，α是一个空间频率变量；ω是激励信号的角频率；U和H是传输矩阵；K是放大系数，J₁(x)是第一类一阶贝塞尔函数；z_k为k和k+1层之间的界面深度；σ_k表示k层的电导率，μ_k表示k层的磁导率，μ_k＝1；where α is a spatial frequency variable; ω is the angular frequency of the excitation signal; U and H are the transmission matrices; K is the amplification factor, J ₁ (x) is the first-order Bessel function of the first kind; z _k is k and the interface depth between layers k+1; σ _k represents the electrical conductivity of the k layer, μ _k represents the magnetic permeability of the k layer, μ _k =1;

(3)根据电感值变化量，计算在各个设定的激励频率下的电感值；(3) Calculate the inductance value at each set excitation frequency according to the change amount of the inductance value;

(4)向空芯传感器分别施加激励电流为I，频率为上述设定的各个激励频率激励信号，由信号采集单元采集其感应信号感应电压U，并送入上位计算机，通过感应电压U和激励电流I得到传感器的测量电感值；(4) Apply the excitation current to the air-core sensor as I, and the frequency is the excitation signal of each excitation frequency set above. The signal acquisition unit collects the induction signal induction voltage U, and sends it to the host computer. Through the induction voltage U and excitation The current I obtains the measured inductance value of the sensor;

(5)寻求在最小二乘意义下的扫频电感值，得到正常皮肤的电导率σ₁ ^/Lσ_n ^/，并将其存在上位计算机里，作为标定值；(5) Find the frequency sweep inductance value in the sense of least squares, obtain the conductivity σ ₁ ^/ Lσ _n ^/ of normal skin, and store it in the host computer as a calibration value;

(6)再测量待测皮肤，重复步骤(1)至(5)，测量得到待测皮肤的电导率；(6) Measure the skin to be tested again, repeat steps (1) to (5), and measure the conductivity of the skin to be tested;

(7)上位计算机通过对比待测皮肤的电导率与正常皮肤的电导率，设定一个阀值，当待测皮肤的电导率与正常皮肤的电导率得差值大于该阀值时，即可判断待测皮肤内含有肿瘤或者异物的成分，否则没有异物。(7) The host computer sets a threshold by comparing the conductivity of the skin to be tested with that of normal skin, and when the difference between the conductivity of the skin to be tested and that of normal skin is greater than the threshold, the It is judged that the skin to be tested contains components of tumor or foreign matter, otherwise there is no foreign matter.

步骤(5)利用Newton-Raphson方法寻求在最小二乘意义下的扫频电感值。Step (5) Use the Newton-Raphson method to find the frequency-swept inductance value in the sense of least squares.

本发明提供了一种非接触式的方法探测皮肤内是否存在肿瘤或异物，还可以实时探测。与现有技术相比，该方法较实用，方便，是最具可行性的皮肤内肿瘤或异物的探测工具之一。The invention provides a non-contact method for detecting whether there is a tumor or a foreign object in the skin, and can also detect in real time. Compared with the prior art, the method is more practical and convenient, and is one of the most feasible detection tools for tumors or foreign objects in the skin.

附图说明 Description of drawings

图1是本发明的基于空芯传感器的皮肤内异物探测装置结构框图。Fig. 1 is a structural block diagram of a device for detecting foreign matter in the skin based on a hollow sensor of the present invention.

具体实施方法Specific implementation method

下面结合附图和实施例对本发明做进一步详述。The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

图1是按照本发明的基于空芯传感器的皮肤内异物探测装置结构框图。它由空芯传感器(即图中的线圈，该线圈是一种空芯线圈)、信号发生单元、信号采集单元、功率放大器和上位计算机六部分构成。信号发生单元采用直接数字合成(DDS)芯片AD7008，该芯片可以产生不同幅度和相位的正弦激励信号。激励信号的幅值和相位可由计算机设置，通过功率放大器放大后加装在激励线圈上。计算机控制信号采集单元，对线圈采集与激励电流相位相差90度的感应电压值。Fig. 1 is a structural block diagram of an intradermal foreign body detection device based on a hollow sensor according to the present invention. It consists of an air-core sensor (that is, the coil in the figure, which is an air-core coil), a signal generating unit, a signal acquisition unit, a power amplifier and a host computer. The signal generation unit adopts direct digital synthesis (DDS) chip AD7008, which can generate sinusoidal excitation signals with different amplitudes and phases. The amplitude and phase of the excitation signal can be set by the computer, amplified by the power amplifier and installed on the excitation coil. The computer controls the signal acquisition unit to collect the induced voltage value with a phase difference of 90 degrees between the coil and the excitation current.

线圈由绝缘导线绕制而成，绕线的直径为0.01mm-10mm，绕线的匝数为1-1000匝，线圈的直径为5mm-100mm。线圈架为非导电材料制成，比如塑料等。The coil is made of insulated wire, the diameter of the winding is 0.01mm-10mm, the number of turns of the winding is 1-1000 turns, and the diameter of the coil is 5mm-100mm. The coil frame is made of non-conductive material, such as plastic.

皮肤为层状结构，皮肤内肿瘤或异物的探测包含正问题和逆问题。将线圈放置距离皮肤一定高度移动，首先标定正常的皮肤，通过给定的正常皮肤的电导率(或磁导率)分布，通过一定的算法即给定的电导率(或磁导率)分布计算其对应的扫频电感值，存在上位计算机里，作为标定值，此为正问题；然后测量待测皮肤，上位计算机控制信号发生单元发出的激励信号经过功率放大器后被接在线圈1上，信号采集单元从线圈采集感应信号，其输出被送入上位计算机，通过感应电压和激励电流可得传感器的电感值，再依据一定的算法即扫频电感值重建电导率(或磁导率)分布的过程，此为逆问题，根据重建的电导率分布情况，因肿瘤或异物的电导率或磁导率与正常皮肤的电导率或磁导率明显不同，所以我们就可以判断皮肤内有无肿瘤或异物。The skin has a layered structure, and the detection of tumors or foreign bodies in the skin includes direct and inverse problems. Place the coil at a certain height from the skin and move it. First, calibrate the normal skin, and calculate the given conductivity (or permeability) distribution through a certain algorithm. The corresponding frequency sweep inductance value is stored in the upper computer as a calibration value, which is a positive problem; then the skin to be tested is measured, and the excitation signal sent by the upper computer control signal generation unit is connected to the coil 1 after passing through the power amplifier. The acquisition unit collects the induction signal from the coil, and its output is sent to the host computer. The inductance value of the sensor can be obtained through the induction voltage and excitation current, and then the conductivity (or magnetic permeability) distribution is reconstructed according to a certain algorithm, that is, the frequency sweep inductance value This is an inverse problem. According to the reconstructed electrical conductivity distribution, the electrical conductivity or magnetic permeability of the tumor or foreign body is obviously different from that of normal skin, so we can judge whether there is a tumor or a magnetic permeability in the skin. foreign body.

测量方法具体包括以下步骤：The measurement method specifically includes the following steps:

(1)将空芯传感器置于离正常皮肤一定的高度，设线圈的的电感值为L₀，并设定初始电导率σ_γ＝σ₁Lσ_n和已经测得的线圈，根据算法(i)，我们可以计算得到一定范围激励频率ω₁Lω_m的电感值f(ω₁Lω_m)＝ΔL+L₀；上位计算机控制信号发生单元发出的激励信号经过功率放大器后被接在线圈1上4信号采集单元从空芯传感器采集感应信号，其输出被送入上位计算机，通过感应电压U和激励电流I可得传感器的测量电感值为

根据算法(ii)可得到正常皮肤的电导率σ₁ ^/Lσ_n ^/存在上位计算机里，作为标定值，标定多种类型的皮肤即不同的σ₁ ^/Lσ_n ^/；(1) Place the air-core sensor at a certain height from the normal skin, set the inductance value of the coil to L ₀ , and set the initial conductivity σ _γ = σ ₁ Lσ _n and the measured coil, according to the algorithm (i ), we can calculate the inductance value f(ω ₁ Lω _m )=ΔL+L ₀ for a certain range of excitation frequency ω ₁ Lω _m ; the excitation signal sent by the host computer control signal generation unit is connected to the coil 1 after passing through the power amplifier 4. The signal acquisition unit collects the induction signal from the air-core sensor, and its output is sent to the host computer. The measured inductance value of the sensor can be obtained by the induction voltage U and the excitation current I

According to the algorithm (ii), the conductivity σ ₁ ^/ Lσ _n ^/ of normal skin can be obtained and stored in the host computer as a calibration value to calibrate various types of skin, that is, different σ ₁ ^/ Lσ _n ^/ ;

(2)再测量待测皮肤，重复步骤(1)，可得待测皮肤的电导率；(2) Measure the skin to be tested again, and repeat step (1) to obtain the conductivity of the skin to be tested;

(3)上位计算机通过对比待测皮肤的电导率与正常皮肤的电导率，设定一个阀值，当待测皮肤的电导率与正常皮肤的电导率得差值大于该阀值时，即可判断待测皮肤内含有肿瘤或者异物的成分，否则没有异物。(3) The host computer sets a threshold by comparing the conductivity of the skin to be tested with that of normal skin, and when the difference between the conductivity of the skin to be tested and that of normal skin is greater than the threshold, the It is judged that the skin to be tested contains components of tumor or foreign matter, otherwise there is no foreign matter.

正问题算法(i)：Positive problem algorithm (i):

有关正问题的算法，可参见C.C.Cheng，C.V.Dodd，and W.E.Deeds，″General analysisof probe coils near stratified conductors，″Int.J.Nondestruct.Test.，vol.3，pp.109-130，1971.下面简单介绍本发明采用的正问题算法。For the algorithm of the positive problem, see C.C.Cheng, C.V.Dodd, and W.E.Deeds, "General analysis of probe coils near stratified conductors," Int.J.Nondestruct.Test., vol.3, pp.109-130, 1971. Below Briefly introduce the forward problem algorithm adopted by the present invention.

线圈底部的高度表示为11，线圈顶部的高度表示为12。线圈的匝数为N，内径和外径为r1和r2，线圈高度为L＝12-11。空气芯圆形线圈在皮肤上由皮肤层电导率σ₁Lσ_n引起的电感变化为The height of the bottom of the coil is denoted as 11 and the height of the top of the coil is denoted as 12. The number of turns of the coil is N, the inner and outer diameters are r1 and r2, and the coil height is L=12-11. The inductance change of the air-core circular coil on the skin caused by the conductivity σ ₁ Lσ _n of the skin layer is

$ΔL Δ L ((ω ω)) = = K K {&Integral; &Integral;}_{00}^{\infty \infty} \frac{{P P}^{22} ((α α))}{{α α}^{66}} A A ((α α)) \frac{{U u}_{1212}}{{U u}_{22 twenty two}} dα dα - - - - - - ((11))$

其中，in,

U＝H₂·H₁·H₀ (2)U=H ₂ ·H ₁ ·H ₀ (2)

U为2×2矩阵，U₁₂为该矩阵第一行第二列的数，U₂₂为矩阵第二行第二列的数。U is a 2×2 matrix, U ₁₂ is the number in the first row and second column of the matrix, and U ₂₂ is the number in the second row and second column of the matrix.

${H h}_{k k} = = \frac{11}{22} [\begin{matrix} ((11 - - + + \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{(({α α}_{k k + + 11} - - {α α}_{k k})) \cdot \cdot {z z}_{k k}},, ((11 - - \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{(({α α}_{k k + + 11} + + {α α}_{k k})) \cdot &Center Dot; {z z}_{k k}} \\ ((11 - - \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{((- - {α α}_{k k + + 11} - - {α α}_{k k})) \cdot &Center Dot; {z z}_{k k}},, ((11 + + \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{(({α α}_{k k} - - {α α}_{k k + + 11})) \cdot &Center Dot; {z z}_{k k}} \end{matrix}] - - - - - - ((33))$

$A A ((α α)) = = {(({e e}^{- - α α {h h}_{11}} - - {e e}^{- - α α {h h}_{22}}))}^{22} - - - - - - ((44))$

$P P ((α α)) = = {&Integral; &Integral;}_{{αr αr}_{11}}^{α α {r r}_{22}} x x {J J}_{11} ((x x)) dx dx - - - - - - ((55))$

$K K = = \frac{π π {μ μ}_{00} {N N}^{22}}{{(({l l}_{11} - - {l l}_{22}))}^{22} {(({r r}_{11} - - {r r}_{22}))}^{22}} - - - - - - ((66))$

${α α}_{k k} = = \sqrt{{α α}^{22} + + jω jω {σ σ}_{k k} {μ μ}_{k k}} - - - - - - ((77))$

其中，α是一个空间频率变量；ω是激励信号的角频率；U和H是传输矩阵；K是一个放大系数，J₁(x)是第一类一阶贝塞尔函数。在k和k+1层之间的界面深度为z_k；σ_k表示k层的电导率，μ_k表示k层的磁导率，这里对皮肤的测量，可知μ_k＝1。Among them, α is a spatial frequency variable; ω is the angular frequency of the excitation signal; U and H are transmission matrices; K is an amplification factor, and J ₁ (x) is a first-order Bessel function of the first kind. The depth of the interface between layers k and k+1 is z _k ; σ _k represents the electrical conductivity of layer k, and μ _k represents the magnetic permeability of layer k. Here, the measurement of the skin shows that μ _k =1.

逆问题算法(ii)：Inverse problem algorithm (ii):

有关逆问题的算法，可参见-，″Employment of regularization method in some problemof geophysical interpretation，″Izv.An.Sssr.Fiz.Zem.，vol.1，pp.38-48，1975.下面简单介绍本发明采用的拟问题算法。For the algorithm of the inverse problem, see -, "Employment of regularization method in some problem of geophysical interpretation," Izv.An.Sssr.Fiz.Zem., vol.1, pp.38-48, 1975. Briefly introduce the present invention below The quasi-problem algorithm used.

本发明利用Newton-Raphson方法来寻求在最小二乘意义下的扫频电感值的吻合，这是一种典型的逆问题求解方法。可定义为：The present invention utilizes the Newton-Raphson method to seek the matching of frequency-sweeping inductance values in the sense of least squares, which is a typical inverse problem solving method. can be defined as:

(1)L₀∈R^m是m个频率下扫频电感测量值的向量表达；(1) L ₀ ∈ R ^m is the vector expression of the measured value of frequency sweep inductance at m frequencies;

(2)σ∈Rⁿ是具有n个自由度的电导率分布向量表达；(2) σ∈R ⁿ is the vector expression of conductivity distribution with n degrees of freedom;

(3)f：Rⁿ→R^m是将电导率分布映射到扫频电感测量值的函数；(3) f: R ⁿ → R ^m is a function that maps the conductivity distribution to the frequency-swept inductance measurement;

(4)

是基于重建电导率分布的计算电感测量值和电感实际测值的平方差。(4)

is the squared difference between the calculated inductance measurement based on the reconstructed conductivity profile and the actual measured inductance.

逆问题是找到σ^*使得φ至少达到局部最小。将φ对σ求微分，令其结果为0向量，即：The inverse problem is to find σ ^* such that φ reaches at least a local minimum. Differentiate φ to σ, and let the result be a 0 vector, namely:

φ′＝[f′]^T[f-L₀]＝0 (8)φ'=[f'] ^T [fL ₀ ]=0 (8)

f′就是加科比(Jacobian)矩阵，它是一个M×N的矩阵，定义为f' is the Jacobian matrix, which is an M×N matrix, defined as

${[[{f f}^{' '}]]}_{i i,, j j} = = \frac{&PartialD; &PartialD; {f f}_{i i}}{&PartialD; &PartialD; {σ σ}_{j j}} - - - - - - ((99))$

采用Tikhonov正则化方法，给定的电导率初值向量为σ_γ，并用J来表示f(σ_r)，则：Using the Tikhonov regularization method, the given conductivity initial value vector is σ _γ , and J is used to represent f(σ _r ), then:

Δσ＝[J^TJ+λ·diag(J^TJ)]^-1J^T[f-L₀] (10)Δσ＝[J ^T J+λ·diag(J ^T J)] ^-1 J ^T [fL ₀ ] (10)

λ是正则化参数。σ^*的估计可表示为，λ is a regularization parameter. An estimate of σ ^* can be expressed as,

σ＝Δσ+σ_r σ＝Δσ+ _σr

上两式可以不断迭代，直至找到合适的σ^*使得φ至少达到局部最小。The above two formulas can be iterated continuously until a suitable σ ^* is found so that φ reaches at least a local minimum.

Claims

1. A detection device for tumors or foreign bodies in the skin based on an air-core sensor, comprising an air-core sensor, a signal generating unit, a signal acquisition unit, a power amplifier and a host computer, the air-core sensor being an air-core coil, vertical Placed directly above the skin to be tested at a certain distance, the host computer controls the current excitation signal generating unit to apply the excitation current signal to the air-core coil, and uses the induction signal unit to measure the induced voltage with a phase difference of 90 degrees from the applied excitation current signal.

2 . The device for detecting tumors or foreign objects in the skin based on an air-core sensor according to claim 1 , wherein the diameter of the air-core coil is 5-100 mm. 3 .

3. The detection device for tumors or foreign objects in the skin based on an air-core sensor according to claim 1, characterized in that, the number of winding turns of the coil is between 1-1000; the diameter of the winding is 0.01 Between mm-10mm.

4. A method for detecting tumors or foreign bodies in the skin based on the hollow sensor according to claim 1, comprising the following steps:

(1) Divide the tissue in the skin into n layers, and set the initial conductivity σ _γ =σ ₁ Lσ _n of each layer,

(2) Place the air-core sensor at a certain height from the normal skin, let the height of the coil bottom be l ₁ , the height of the top of the coil be l ₂ , the number of turns of the coil be N, the inner and outer diameters be r1 and r2, set the coil The inductance value of the sensor is L ₀ , and the excitation frequency of the air-core sensor is ω ₁ Lω _m , and the inductance value variation at different excitation frequencies is calculated according to the following formula:

Δ L (ω) = K {&Integral;}_{0}^{\infty} \frac{P^{2} (α)}{α^{6}} A (α) \frac{u_{12}}{u_{twenty two}} dα,

in,

U=H ₂ ·H ₁ ·H ₀ , U is a 2×2 matrix, U ₁₂ is the number in the first row and second column of the matrix, U ₂₂ is the number in the second row and second column of the matrix,

{H h}_{k k} = = \frac{11}{22} [\begin{matrix} ((11 - - + + \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{(({α α}_{k k + + 11} - - {α α}_{k k})) \cdot \cdot {z z}_{k k}},, ((11 - - \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{(({α α}_{k k + + 11} + + {α α}_{k k})) \cdot &Center Dot; {z z}_{k k}} \\ ((11 - - \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{((- - {α α}_{k k + + 11} - - {α α}_{k k})) \cdot &Center Dot; {z z}_{k k}},, ((11 + + \frac{{α α}_{k k}}{{α α}_{k k + + 11}})) {e e}^{(({α α}_{k k} - - {α α}_{k k + + 11})) \cdot &Center Dot; {z z}_{k k}} \end{matrix}],,

P P ((α α)) = = {&Integral; &Integral;}_{{αr αr}_{11}}^{α α {r r}_{22}} x x {J J}_{11} ((x x)) dx dx,,

K K = = \frac{π π {μ μ}_{00} {N N}^{22}}{{(({l l}_{11} - - {l l}_{22}))}^{22} {(({r r}_{11} - - {r r}_{22}))}^{22}},,

{α α}_{k k} = = \sqrt{{α α}^{22} + + jω jω {σ σ}_{k k} {μ μ}_{k k}},,

where α is a spatial frequency variable; ω is the angular frequency of the excitation signal; U and H are the transmission matrices; K is the amplification factor, J ₁ (x) is the first-order Bessel function of the first kind; z _k is k and the interface depth between layers k+1; σ _k represents the electrical conductivity of the k layer, μ _k represents the magnetic permeability of the k layer, μ _k =1;

(3) Calculate the inductance value at each set excitation frequency according to the change amount of the inductance value;

(4) Apply the excitation current to the air-core sensor as I, and the frequency is the excitation signal of each excitation frequency set above. The signal acquisition unit collects the induction signal induction voltage U, and sends it to the host computer. Through the induction voltage U and excitation The current I obtains the measured inductance value of the sensor;

(5) Find the frequency sweep inductance value in the sense of least squares, obtain the conductivity σ ₁ ^/ Lσ _n ^/ of normal skin, and store it in the host computer as a calibration value;

(6) Measure the skin to be tested again, repeat steps (1) to (5), and measure the conductivity of the skin to be tested;

(7) The host computer sets a threshold by comparing the conductivity of the skin to be tested with that of normal skin, and when the difference between the conductivity of the skin to be tested and that of normal skin is greater than the threshold, the It is judged that the skin to be tested contains components of tumor or foreign matter, otherwise there is no foreign matter.

5 . The method for detecting tumors or foreign objects in the skin according to claim 4 , wherein the step (5) utilizes the Newton-Raphson method to find the frequency-sweeping inductance value in the sense of least squares. 6 .