磁探測電阻抗成像的若干關(guān)鍵技術(shù)研究
發(fā)布時間：2018-11-09 09:40
【摘要】：生物體可以看作是由具有不同電特性并且按照一定空間位置分布的多種生物組織所構(gòu)成的混合導(dǎo)體，生物組織的空間電導(dǎo)率分布可以提供解剖結(jié)構(gòu)、功能活動和生理病理狀態(tài)的有用信息。電阻抗成像技術(shù)以生物體內(nèi)電阻抗的分布或變化為成像目標體，是一種集形態(tài)、結(jié)構(gòu)和功能成像于一體的新一代無創(chuàng)生物醫(yī)學(xué)檢測與成像技術(shù)。它通過對成像目標體外加一定的安全激勵電流，測量成像目標體表面的邊界電壓，從而重構(gòu)得到其內(nèi)部的阻抗分布。然而電阻抗成像通過電極以接觸的方式測量邊界電壓，不僅獲得的測量信息量小，并且測量精度還受到許多干擾因素的影響，例如皮膚表面濕度與粗糙程度以及測量時所施加的壓力等。 磁探測電阻抗成像通過表面電極向成像目標體注入激勵電流，利用磁場傳感器非接觸測量成像目標體周圍的磁場，然后根據(jù)磁場數(shù)據(jù)重構(gòu)得到電阻抗分布圖像。磁探測電阻抗成像作為電阻抗成像的一個分支，采用非接觸測量的方式測量成像目標體周圍的磁場來重建其內(nèi)部電阻抗分布，磁場傳感器的定位精度高，并且測量傳感器不與成像目標體接觸。磁探測電阻抗成像技術(shù)克服了電阻抗成像接觸式測量的缺點，又結(jié)合了電阻抗成像的廉價、無創(chuàng)和連續(xù)圖像監(jiān)護等諸多優(yōu)點。本文致力于磁探測電阻抗成像的研究，探討了正問題、逆問題、測量方式優(yōu)化和數(shù)據(jù)采集等若干關(guān)鍵問題，為磁探測電阻抗成像技術(shù)的發(fā)展奠定了基礎(chǔ)。 首先描述了磁探測電阻抗成像的正問題，并且利用有限元方法和已知的電流邊界條件求解得到目標體內(nèi)部的電壓和電流密度分布，然后根據(jù)Biot-Savart定律獲得目標體外部的磁感應(yīng)強度數(shù)據(jù)。在此基礎(chǔ)上，比較了各種電極模式下的正問題計算結(jié)果，并且提出了環(huán)形電極模式。環(huán)形電極避免了電流的擴散效應(yīng)，使得磁探測電阻抗成像簡化成磁探測電流密度成像，并且縮短了測量時間和圖像重建時間，為快速成像奠定了基礎(chǔ)。 介紹了磁探測電阻抗成像的電流密度類算法，磁通密度類算法和差分成像方法。針對磁探測電阻抗成像逆問題的不適定性，提出基于全變差正則化的圖像重建算法和適用于稀疏圖像重建的全變差正則化和1范數(shù)正則化的混合正則化算法。與常用的2范數(shù)正則化算法相比，全變差正則化不僅改善了磁探測電阻抗成像逆問題的病態(tài)性，還具有良好的保邊緣性，使得重構(gòu)圖像的介質(zhì)之間的邊界更加清晰，，提高了重建圖像的質(zhì)量�；旌险齽t化算法使得重建圖像不僅具有清晰的邊界，而且保證了稀疏特性，更好地實現(xiàn)了目標的定位。仿真結(jié)果表明了提出的正則化算法的有效性，推動了磁探測電阻抗成像技術(shù)的研究和發(fā)展。 激勵電極的大小、位置、數(shù)量和測量點的位置、數(shù)量等測量配置參數(shù)會影響磁探測電阻抗成像的質(zhì)量。首先利用奇異值分析方法對不同測量配置參數(shù)進行了評估和優(yōu)化，然后利用減少冗余法對每個測量點提供的信息量進行測量和評估，去掉提高較少信息量的冗余測量點，在減少測量點的情況下幾乎不損失有用信息，從而對測量配置進行了進一步的優(yōu)化。圖像重建實驗驗證了奇異值分析和減少冗余法的有效性。結(jié)果表明適當?shù)卦黾蛹铍姌O的數(shù)量，測量點分布的圓周數(shù)和測量點數(shù)目都可以增加有效奇異值個數(shù)，另外將激勵電極盡量靠近感興趣區(qū)域也可以增加有效奇異值個數(shù)。奇異值分析和減少冗余法是有效地尋找最優(yōu)測量配置的方法，為磁探測電阻抗成像實驗設(shè)計提供了有效而可靠的工具。 建立了一套基于數(shù)據(jù)采集卡的磁探測電阻抗成像數(shù)據(jù)采集系統(tǒng)，包括恒流激勵源、磁場傳感器、后續(xù)信號放大和濾波電路、信號采集及控制單元和機械掃描裝置等，并且利用LabVIEW設(shè)計了基于多測量點的自動數(shù)據(jù)采集和保存系統(tǒng)。在此基礎(chǔ)上以離散模型、生理鹽水模型和瓊脂模型為實驗對象，采用環(huán)形電極和橫向電流加載模式進行了相關(guān)實驗，驗證了磁探測電阻抗成像的可行性，將磁探測電阻抗成像向前推進了一步。
[Abstract]:The organism can be regarded as a mixed conductor composed of a plurality of biological tissues with different electrical characteristics and distributed according to a certain spatial position, and the spatial conductivity distribution of the biological tissue can provide useful information of the anatomical structure, the functional activity and the physiological and pathological state. The electrical impedance imaging technology is a new generation of non-invasive biomedical detection and imaging technology integrating form, structure and function. and the boundary voltage of the surface of the imaging target body is measured by adding a certain safety excitation current to the imaging target body, so that the impedance distribution inside the imaging target body is reconstructed. However, the electrical impedance imaging measures the boundary voltage in such a way that the electrode is in contact, not only the amount of measurement information obtained is small, and the measurement accuracy is also affected by many interference factors, such as the surface humidity and roughness of the skin, and the pressure applied at the time of measurement, and the like. the magnetic detection electric impedance imaging is used for injecting the excitation current to the imaging target body through the surface electrode, the magnetic detection electro-impedance imaging is used as a branch of the electrical impedance imaging, the magnetic field around the imaging target body is measured in a non-contact measurement way to reconstruct the internal electrical impedance distribution, the positioning accuracy of the magnetic field sensor is high, and the measurement sensor is not in contact with the imaging target body The magnetic detection electro-impedance imaging technology overcomes the shortcomings of the contact measurement of the electrical impedance imaging, and also combines the low-cost, non-invasive and continuous image monitoring of the electrical impedance imaging. This paper is devoted to the research of the electrical impedance imaging of magnetic detection, and probes into some key problems, such as positive and inverse problems, optimization of measurement methods and data acquisition, and lays a foundation for the development of the magnetic detection electric impedance imaging technology. Based on the method of finite element method and known current boundary condition, the voltage and current density distribution inside the object body are obtained, and then the magnetic induction outside the object body is obtained according to the Biot-Savart law. Based on this, the calculation of positive problems in various electrode modes is compared, and the ring is put forward. The ring-shaped electrode avoids the diffusion effect of the current, so that the magnetic detection electric impedance imaging is simplified into the magnetic detection current density imaging, the measurement time and the image reconstruction time are shortened, The current density class of the magnetic detection electric impedance imaging is introduced, and the flux density class is calculated. An image reconstruction algorithm based on total variation regularization and a total variation regularized and 1-norm regularization for sparse image reconstruction are proposed for the discomforts of the inverse problem of the magnetic detection electrical impedance imaging. Compared with the conventional two-norm regularization algorithm, the total variation regularization not only improves the ill-condition of the inverse problem of the magnetic detection electro-impedance imaging, but also has good edge-preserving property, so that the boundary between the medium of the reconstructed image is more clear and improved, The quality of the reconstructed image is reconstructed. The hybrid regularization algorithm makes the reconstructed image not only have a clear boundary, but also the sparse properties, and better The simulation results show that the proposed regularization algorithm is effective, and the magnetic detection electro-impedance imaging is promoted. Research and development of technology. The size, position, number of excitation electrodes and the location and quantity of measuring points will affect the measurement and configuration parameters. The method of singular value analysis is used to evaluate and optimize the different measurement configuration parameters, then the information quantity provided by each measurement point is measured and evaluated by the method of reducing the redundancy, and the improvement is removed. a redundant measurement point with less information, with little loss of useful information in the event of a reduction in the measurement point, The configuration has been further optimized. The image reconstruction experiment verifies the singular value. The results show that the number of effective singular values can be increased by appropriately increasing the number of excitation electrodes, the number of the circumference of the distribution of the measuring points and the number of measuring points can increase the number of effective singular values, and the excitation electrodes are as close as possible to the region of interest. The number of effective singular values can be increased. The singular value analysis and the reduction of the redundancy method are the effective way to find the optimal measurement configuration, which is an experimental design of the magnetic detection electrical impedance imaging. The invention provides an effective and reliable tool, and a magnetic detection electric impedance imaging data acquisition system based on a data acquisition card is established, Set and control unit and mechanical scanning device, etc., and design the multi-test based on LabVIEW Based on the discrete model, physiological saline model and agar model as the experimental object, the experimental results are carried out by using the model of the discrete model, the physiological saline model and the agar model, and the feasibility of the magnetic detection of the electrical impedance imaging is verified.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號】：R310
本文編號：2320046
[Abstract]:The organism can be regarded as a mixed conductor composed of a plurality of biological tissues with different electrical characteristics and distributed according to a certain spatial position, and the spatial conductivity distribution of the biological tissue can provide useful information of the anatomical structure, the functional activity and the physiological and pathological state. The electrical impedance imaging technology is a new generation of non-invasive biomedical detection and imaging technology integrating form, structure and function. and the boundary voltage of the surface of the imaging target body is measured by adding a certain safety excitation current to the imaging target body, so that the impedance distribution inside the imaging target body is reconstructed. However, the electrical impedance imaging measures the boundary voltage in such a way that the electrode is in contact, not only the amount of measurement information obtained is small, and the measurement accuracy is also affected by many interference factors, such as the surface humidity and roughness of the skin, and the pressure applied at the time of measurement, and the like. the magnetic detection electric impedance imaging is used for injecting the excitation current to the imaging target body through the surface electrode, the magnetic detection electro-impedance imaging is used as a branch of the electrical impedance imaging, the magnetic field around the imaging target body is measured in a non-contact measurement way to reconstruct the internal electrical impedance distribution, the positioning accuracy of the magnetic field sensor is high, and the measurement sensor is not in contact with the imaging target body The magnetic detection electro-impedance imaging technology overcomes the shortcomings of the contact measurement of the electrical impedance imaging, and also combines the low-cost, non-invasive and continuous image monitoring of the electrical impedance imaging. This paper is devoted to the research of the electrical impedance imaging of magnetic detection, and probes into some key problems, such as positive and inverse problems, optimization of measurement methods and data acquisition, and lays a foundation for the development of the magnetic detection electric impedance imaging technology. Based on the method of finite element method and known current boundary condition, the voltage and current density distribution inside the object body are obtained, and then the magnetic induction outside the object body is obtained according to the Biot-Savart law. Based on this, the calculation of positive problems in various electrode modes is compared, and the ring is put forward. The ring-shaped electrode avoids the diffusion effect of the current, so that the magnetic detection electric impedance imaging is simplified into the magnetic detection current density imaging, the measurement time and the image reconstruction time are shortened, The current density class of the magnetic detection electric impedance imaging is introduced, and the flux density class is calculated. An image reconstruction algorithm based on total variation regularization and a total variation regularized and 1-norm regularization for sparse image reconstruction are proposed for the discomforts of the inverse problem of the magnetic detection electrical impedance imaging. Compared with the conventional two-norm regularization algorithm, the total variation regularization not only improves the ill-condition of the inverse problem of the magnetic detection electro-impedance imaging, but also has good edge-preserving property, so that the boundary between the medium of the reconstructed image is more clear and improved, The quality of the reconstructed image is reconstructed. The hybrid regularization algorithm makes the reconstructed image not only have a clear boundary, but also the sparse properties, and better The simulation results show that the proposed regularization algorithm is effective, and the magnetic detection electro-impedance imaging is promoted. Research and development of technology. The size, position, number of excitation electrodes and the location and quantity of measuring points will affect the measurement and configuration parameters. The method of singular value analysis is used to evaluate and optimize the different measurement configuration parameters, then the information quantity provided by each measurement point is measured and evaluated by the method of reducing the redundancy, and the improvement is removed. a redundant measurement point with less information, with little loss of useful information in the event of a reduction in the measurement point, The configuration has been further optimized. The image reconstruction experiment verifies the singular value. The results show that the number of effective singular values can be increased by appropriately increasing the number of excitation electrodes, the number of the circumference of the distribution of the measuring points and the number of measuring points can increase the number of effective singular values, and the excitation electrodes are as close as possible to the region of interest. The number of effective singular values can be increased. The singular value analysis and the reduction of the redundancy method are the effective way to find the optimal measurement configuration, which is an experimental design of the magnetic detection electrical impedance imaging. The invention provides an effective and reliable tool, and a magnetic detection electric impedance imaging data acquisition system based on a data acquisition card is established, Set and control unit and mechanical scanning device, etc., and design the multi-test based on LabVIEW Based on the discrete model, physiological saline model and agar model as the experimental object, the experimental results are carried out by using the model of the discrete model, the physiological saline model and the agar model, and the feasibility of the magnetic detection of the electrical impedance imaging is verified.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號】：R310
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