面向生物磁感應成像的線圈陣列優(yōu)化與測量方法研究
本文選題:生物磁感應成像 + 耦合模型 ; 參考:《南京理工大學》2017年碩士論文
【摘要】:磁感應斷層成像技術作為一種新興的非接觸式生物組織成像技術,是當今生物醫(yī)學工程無損檢測的熱點之一。針對生物磁感應成像中強背景下有效信號的提取難題,開展面向生物磁感應成像線圈陣列優(yōu)化和測量方法的研究,以提高測量信號的信噪比。根據(jù)電磁感應耦合理論,基于生物EMT檢測系統(tǒng)線圈傳感器和被測生物組織的電路模型分別對其阻抗特性進行了仿真計算與分析,采用等效電路法建立了生物電磁感應層析成像的諧振能量耦合模型;贛atlab的數(shù)值分析,得出了線圈品質因數(shù)、耦合系數(shù)、傳感器安裝個數(shù)及位置等參數(shù)對耦合模型的影響,確定了激勵線圈品質因數(shù)為影響傳感器及測量系統(tǒng)輸出的關鍵調控因素。針對檢測線圈與激勵線圈之間的干擾問題,提出了空間陣列四通道生物EMT檢測模型,并對該檢測模型的特性進行了仿真分析與研究;根據(jù)現(xiàn)有的激勵傳感器參數(shù),基于虛擬正交響應面法對激勵傳感器的參數(shù)進行了仿真優(yōu)化;基于相關分析方法實驗研究了檢測線圈傳感器的選取與匹配;針對高頻成像系統(tǒng)容易受到外界的噪聲干擾,引入屏蔽技術,對屏蔽層的關鍵參數(shù)進行了仿真與實驗研究,并完成了傳感器陣列載體結構的設計及材料選型。設計了生物EMT檢測電路,確定了鑒相方法。仿真分析了高頻特征下FFT等鑒相算法的鑒相精度與采樣率及信噪比之間的關系;分析了檢測線圈空場試驗下所疊加的噪聲特性,采用小波去噪與中值濾波的混合去噪方法可以有效抑制高斯及脈沖干擾。實驗研究了低電導率鹽溶液空間位置變化、電導率變化及異物干擾對檢測系統(tǒng)輸出信號的影響,實驗結果表明,基于正交差分的空間陣列EMT系統(tǒng)在減小了線圈間的耦合作用下,提高了成像系統(tǒng)的靈敏度,且系統(tǒng)檢測線性區(qū)間的下限值提高至0.25S/m,在0.60~1.40S/m范圍內線性化程度較高;針對旋轉測量周期長的問題,進行了旋轉測量方法的優(yōu)化,在均勻被測物下利用多通道線圈數(shù)據(jù)融合測量可以有效減少檢測數(shù)據(jù)的冗余輸出。
[Abstract]:As a new non-contact tissue imaging technique, magnetic induction tomography (MRT) is one of the hot spots in biomedical engineering nondestructive testing (NDT). In order to improve the signal-to-noise ratio (SNR) of biomagnetic induction imaging, the optimization of coil array and the measurement method are studied in order to improve the signal to noise ratio (SNR) of the measured signal. Based on the electromagnetic induction coupling theory, the impedance characteristics of the system are simulated and analyzed based on the circuit model of the coil sensor and the biological tissue of the biological EMT detection system. The resonant energy coupling model of biological electromagnetic induction tomography is established by using equivalent circuit method. Based on the numerical analysis of Matlab, the influence of the parameters such as coil quality factor, coupling coefficient, sensor installation number and position on the coupling model is obtained. The quality factor of the exciting coil is determined as the key control factor affecting the output of the sensor and the measuring system. Aiming at the interference between the detection coil and the excitation coil, a four-channel biological EMT detection model of space array is proposed, and the characteristics of the detection model are simulated and analyzed. Based on the virtual orthogonal response surface method, the parameters of the excitation sensor are simulated and optimized. Based on the correlation analysis method, the selection and matching of the detection coil sensor are studied experimentally. The key parameters of the shield layer are simulated and experimentally studied by introducing the shielding technology, and the design of the sensor array carrier structure and the selection of the material are completed. The biological EMT detection circuit is designed and the phase detection method is determined. The relationship between phase detection accuracy and sampling rate and signal-to-noise ratio (SNR) of FFT equal-phase detection algorithm under high frequency characteristic is analyzed, and the superposition noise characteristic of detection coil in empty field test is analyzed. The mixed method of wavelet denoising and median filtering can effectively suppress Gao Si and pulse interference. The effects of the change of the spatial position of the low conductivity salt solution, the change of the conductivity and the foreign body interference on the output signal of the detection system are studied experimentally. The experimental results show that the spatial array EMT system based on orthogonal difference can reduce the coupling between the coils. The sensitivity of the imaging system is improved, and the lower limit of the detection linear range of the system is raised to 0.25 S / m, and the degree of linearization is higher in the 0.60~1.40S/m range. The rotation measurement method is optimized to solve the problem of long rotation measurement period. The redundant output of detection data can be effectively reduced by using multi-channel coils data fusion measurement under uniform measurement.
【學位授予單位】:南京理工大學
【學位級別】:碩士
【學位授予年份】:2017
【分類號】:R318;TP391.41
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