【摘要】：人體組織器官具有獨(dú)特的電特性(阻抗、導(dǎo)納、介電常數(shù)等),在新陳代謝過程中出現(xiàn)生理和病理狀態(tài)改變就會(huì)引起相應(yīng)電特性的改變。生物電阻抗技術(shù)(Electrical Bioimpedance Technology)是利用生物組織與器官的電特性及其變化提取相關(guān)信息的無損傷檢測技術(shù)。其最大優(yōu)勢在于提取與人體生理病理狀態(tài)相聯(lián)系的功能性或前瞻性信息,具有無創(chuàng)、廉價(jià)、安全、無毒無害和信息豐富的特點(diǎn),廣泛應(yīng)用于心、腦、肺血管及循環(huán)系統(tǒng)功能檢測,腫瘤的早期發(fā)現(xiàn)和診斷,胃動(dòng)力學(xué)檢測,人體組成成份測定,電阻抗斷層成像(Electrical Impedance Tomography, EIT)等。 本研究在總結(jié)生物電阻抗技術(shù)的研究進(jìn)展和測量理論發(fā)展的基礎(chǔ)上,針對多頻、復(fù)阻抗生物電阻抗測量的要求,研究以FPGA芯片為核心通用型數(shù)字化生物電阻抗測量實(shí)驗(yàn)平臺,具體工作如下： 1、分析生物電阻抗技術(shù)的發(fā)展動(dòng)態(tài),提出數(shù)字化多頻、復(fù)阻抗測量系統(tǒng)這一研究目標(biāo),基于FPGA的數(shù)字系統(tǒng)開發(fā)與設(shè)計(jì)方法,設(shè)計(jì)實(shí)驗(yàn)平臺的結(jié)構(gòu)框圖,并規(guī)劃各模塊的功能。 2、基于FPGA和DDS技術(shù)設(shè)計(jì)了輸出頻率為6.1KHz～1562.5KHz的數(shù)字信號發(fā)生器,采用改進(jìn)的Howland電路由THS4021芯片構(gòu)建恒流激勵(lì)源,其輸出阻抗有較好的頻率穩(wěn)定性,在6.1KHz～97.7KHz的范圍內(nèi)輸出阻抗維持在200KΩ附近,當(dāng)頻率為390.6KHz時(shí)輸出阻抗可保持在170KΩ。 3、采用基于FPAG的數(shù)字技術(shù),依據(jù)生物阻抗信號的正交解調(diào)方法,構(gòu)建了高質(zhì)量正交解調(diào)和串口通信等模塊。能同時(shí)獲取被測阻抗信號的實(shí)部和虛部信息,完成數(shù)據(jù)采集和傳送等功能,用于復(fù)阻抗全信息測量。 4、進(jìn)行了電阻、電容和三元件模型的測試實(shí)驗(yàn)和誤差分析,驗(yàn)證了本研究平臺的有效性和準(zhǔn)確性；基于16電極鹽水槽實(shí)驗(yàn)系統(tǒng),采用相鄰激勵(lì)-相鄰測量模式進(jìn)行了EIT鹽水槽成像實(shí)驗(yàn),初步驗(yàn)證了本研究平臺用于EIT測量的可行性。 最后對研究工作進(jìn)行了總結(jié),并對今后進(jìn)一步完善研究平臺提出了建議。
[Abstract]:Human tissues and organs have unique electrical properties (impedance, admittance, dielectric constant, etc.). The changes of physiological and pathological state in metabolic process will cause the corresponding changes of electrical properties. Bioelectrical impedance (Electrical Bioimpedance Technology) is a nondestructive detection technique which uses electrical properties and changes of biological tissues and organs to extract relevant information. Its greatest advantage lies in the extraction of functional or forward-looking information related to the physiological and pathological state of the human body. It has the characteristics of non-invasive, cheap, safe, non-toxic and informative, and is widely used in the heart and brain. Detection of pulmonary vascular and circulatory function, early detection and diagnosis of tumor, gastric dynamics, composition of human body, electrical impedance tomography (Electrical Impedance Tomography, EIT), etc. On the basis of summarizing the research progress of bioelectric impedance technology and the development of measurement theory, aiming at the requirement of multi-frequency and complex impedance bioelectrical impedance measurement, this paper studies the FPGA chip as the core and general digital experimental platform for bioelectrical impedance measurement. The main work is as follows: 1. The development trend of bioelectric impedance technology is analyzed. The research goal of digital multi-frequency and complex impedance measurement system is put forward. The development and design method of digital system based on FPGA is presented. The structure block diagram of the experimental platform is designed, and the functions of each module are planned. 2. Based on FPGA and DDS technology, the digital signal generator with output frequency of 6.1KHz~1562.5KHz is designed. The improved Howland circuit is used to construct the constant current excitation source from THS4021 chip. The output impedance has good frequency stability. In the range of 6.1KHz~97.7KHz, the output impedance is kept around 200K 惟, and when the frequency is 390.6KHz, the output impedance can be kept at 170K 惟. 3. The digital technique based on FPAG is used. According to the quadrature demodulation method of biological impedance signal, the high quality quadrature demodulation and serial communication module are constructed. It can simultaneously obtain the real and imaginary part information of the impedance signal under test, complete the functions of data acquisition and transmission, and be used to measure the full information of complex impedance. 4. The testing experiment and error analysis of resistance, capacitance and three-element model are carried out. The validity and accuracy of the research platform are verified. Based on the 16-electrode salt flume experimental system, the EIT salt flume imaging experiment is carried out by using adjacent excitation-adjacent measurement mode, and the feasibility of using this platform for EIT measurement is preliminarily verified. Finally, the research work is summarized and some suggestions are put forward to further improve the research platform in the future.
【學(xué)位授予單位】：北京協(xié)和醫(yī)學(xué)院
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：R318.0

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