本文選題：介電特性　切入點(diǎn)：開端同軸線法　出處：《南方醫(yī)科大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：生物組織介電特性(electricalproperties,EPs)主要包括電導(dǎo)率(σ)和相對(duì)介電常數(shù)(εr),是生物組織在電磁場(chǎng)作用下表現(xiàn)出的電特性。相關(guān)研究已表明人體腫瘤組織與正常組織介電特性存在較大差異,因此人體組織介電特性信息可用于腫瘤的診斷,而且可能為癌癥的早期診斷提供幫助。目前,常用組織介電特性測(cè)量方法有開端同軸線法和磁共振介電特性斷層成像技術(shù)(magnetic resonance electrical property tomography,MR EPT)等,本文首先運(yùn)用開端同軸線法對(duì)結(jié)直腸正常與癌變組織介電特性進(jìn)行了離體測(cè)量;然后對(duì)MR EPT技術(shù)進(jìn)行了初步的理論研究,量化分析了 MR EPT核心算法的重建誤差,并對(duì)該技術(shù)的固有分辨能力進(jìn)行了理論分析。結(jié)直腸正常與癌變組織介電特性離體測(cè)量研究中,首先用開端同軸線法測(cè)量85位結(jié)直腸腫瘤患者的結(jié)直腸切除組織的介電特性;其次用Cole-Cole模型對(duì)測(cè)量結(jié)果進(jìn)行擬合;最后比較正常組織與腫瘤組織介電特性擬合結(jié)果。結(jié)果顯示,正常組織與腫瘤組織介電特性存在較大差異,當(dāng)頻率為128MHz時(shí),腫瘤組織ε和σ分別比正常組織高14.6%和17%。MR EPT核心算法重建誤差研究中,首先量化分析MR EPT核心算法在不同組織交界處的重建誤差,其次對(duì)64MHz、128MHz和298MHz下MR EPT核心算法在非均勻負(fù)載中應(yīng)用時(shí)的重建誤差進(jìn)行比較。結(jié)果顯示,MR EPT核心算法在不同組織交界的重建誤差均不一樣,各組織交界上σ和εr的平均相對(duì)重建誤差分別大于0.3986和0.2218。該算法在非均勻負(fù)載中應(yīng)用時(shí)的重建誤差隨共振頻率的增大而減小,當(dāng)共振頻率為64MHz時(shí),ε和σ的平均相對(duì)重建誤差分別為 28.71%和 9.11%。MREPT固有分辨能力的理論分析中,首先建立一系列具有不同介電特性對(duì)比度的電磁模型,仿真得到模型發(fā)射場(chǎng)B1+,進(jìn)而通過MR EPT核心算法重建電磁模型介電特性;然后對(duì)MR EPT固有分辨能力進(jìn)行定義和評(píng)估;最后對(duì)可能影響MR EPT固有分辨能力的因素進(jìn)行分析。結(jié)果顯示,MR EPT固有分辨能力與ROI大小正相關(guān),MR EPT最大固有電導(dǎo)率分辨能力和相對(duì)介電常數(shù)分辨能力均為1/1.02。本文對(duì)結(jié)直腸正常與癌變組織介電特性進(jìn)行了離體測(cè)量,并對(duì)MR EPT技術(shù)進(jìn)行了初步的理論研究。結(jié)直腸組織離體測(cè)量研究表明結(jié)直腸腫瘤組織與正常組織介電特性存在較大差異,所測(cè)結(jié)果可作為介電特性相關(guān)研究的基礎(chǔ)數(shù)據(jù);MR EPT技術(shù)的初步理論研究對(duì)降低MR EPT核心算法在非均勻組織中的重建誤差,實(shí)現(xiàn)高精度的MR EPT技術(shù)有一定的參考價(jià)值,為早日將MR EPT技術(shù)應(yīng)用到腫瘤早期診斷中做出了貢獻(xiàn)。
[Abstract]:The dielectric properties of biological tissues mainly include electrical conductivity (蟽) and relative dielectric constant (蔚 r), which are the electrical properties of biological tissues under the action of electromagnetic field. Relevant studies have shown that there are great differences between the dielectric properties of human tumor tissues and normal tissues. Therefore, the information of dielectric properties of human tissues can be used in the diagnosis of cancer, and may be helpful for the early diagnosis of cancer. The common methods for measuring the dielectric properties of colorectal cancer tissues are starting coaxial method and resonance electrical property tomographic imaging technique. In this paper, the dielectric properties of colorectal normal and cancerous tissues are measured in vitro by the method of starting coaxial line. Then, the theory of Mr EPT technology is studied, and the reconstruction error of Mr EPT core algorithm is analyzed quantitatively. In the in vitro measurement of the dielectric characteristics of colorectal normal and cancerous tissues, the dielectric properties of 85 colorectal cancer patients were measured by starting coaxial method. Secondly, the measured results were fitted with Cole-Cole model, and the dielectric characteristics of normal tissue and tumor tissue were compared. The results showed that the dielectric characteristics of normal tissue and tumor tissue were different, when the frequency was 128MHz, The reconstruction error of Mr EPT core algorithm is 14.6% and 17.5% higher than that of normal tissue, respectively. Firstly, the reconstruction error of Mr EPT core algorithm at the junction of different tissues is analyzed quantitatively. Secondly, the reconstruction error of Mr EPT core algorithm at 128MHz and 298MHz is compared. The results show that the reconstruction error of Mr EPT core algorithm is different at the junction of different tissues. The average relative reconstruction errors of 蟽 and 蔚 r at the junctions of tissues are greater than 0.3986 and 0.2218, respectively. The reconstruction error decreases with the increase of resonance frequency. When the resonance frequency is 64MHz, the average relative reconstruction errors of 蔚 and 蟽 are 28.71% and 9.11 respectively. In the theoretical analysis of intrinsic resolution of MREPT, a series of electromagnetic models with different contrast of dielectric properties are established, and the emulation results of the emitter B1 are obtained. Then the dielectric properties of the electromagnetic model are reconstructed by Mr EPT core algorithm, and the inherent resolution of Mr EPT is defined and evaluated. Finally, the factors that may affect the inherent resolution of Mr EPT are analyzed. The results show that the intrinsic resolution of Mr EPT is positively correlated with the magnitude of ROI. The resolution of the maximum intrinsic conductivity and the relative dielectric constant of Mr EPT are both 1 / 1.02. The dielectric properties of colorectal normal and cancerous tissues were measured in vitro. The in vitro measurement of colorectal tissue showed that the dielectric properties of colorectal tumor tissues were different from those of normal tissues. The measured results can be used as the basic data for the study of dielectric properties. The preliminary theoretical study of Mr EPT technique has some reference value for reducing the reconstruction error of Mr EPT core algorithm in non-uniform tissue and realizing high precision Mr EPT technology. It has contributed to the early application of Mr EPT technique in the early diagnosis of tumor.
【學(xué)位授予單位】：南方醫(yī)科大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：R730.4;R445.2

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