【摘要】：溫度是腫瘤診斷與熱療治療的關(guān)鍵參數(shù),也是現(xiàn)代生物熱物理與信息學科研究的前沿交叉領(lǐng)域的重要指標。針對在生物體內(nèi)復雜的生化環(huán)境,基于磁納米粒子溫度敏感性的磁納米溫度測量方法被認為是一種有效的非侵入式的測溫手段。本文針對腫瘤熱療提出的高精度與快速響應(yīng)的溫度測量系統(tǒng)需求,優(yōu)化升級現(xiàn)有低頻磁場激勵下的磁納米溫度測量方法,研究了磁納米粒子在中高頻時變激勵磁場下的動態(tài)特性(磁弛豫現(xiàn)象)并在此基礎(chǔ)上提出了中高頻時變磁場激勵磁納米溫度測量方法。全文的具體內(nèi)容如下：首先,為提高溫度測量精度,在現(xiàn)有低頻時變磁場激勵下磁納米溫度測量方法基礎(chǔ)上,本文分析了模型中的參數(shù)對溫度測量精度的影響,研究設(shè)計了磁納米粒子的粒徑的大小及離散激勵磁場的優(yōu)化方法。實驗結(jié)果發(fā)現(xiàn),激勵磁場大小相同的前提下,溫度測量精度隨著超順磁性磁納米粒子的粒徑的增大而提高。此外,本文對激勵磁場的離散分布進行優(yōu)化,優(yōu)化結(jié)果表明該方法可使溫度測量精度提高30%。優(yōu)化方法可用于細胞內(nèi)等特殊環(huán)境下的溫度測量。其次,為提高溫度測量速度,本文研究了磁納米粒子在中高頻時變磁場激勵下的動態(tài)特性(磁弛豫現(xiàn)象)。通過研究布洛赫弛豫方程,分析了磁納米粒子在時變磁場激勵下的磁化響應(yīng)隨時間的變化關(guān)系。實驗結(jié)果分析發(fā)現(xiàn)在中高頻磁場激勵下,超順磁性的磁納米粒子表現(xiàn)出的磁滯現(xiàn)象導致了現(xiàn)有低頻磁場激勵下的溫度測量技術(shù)不再適用于中高頻時變磁場激勵的情形。基于此,有必要研究在中高頻磁場激勵下的磁納米溫度測量方法。為了研究在中高頻激勵磁場下的磁納米溫度測量方法,本文利用布洛赫弛豫方程將描述磁納米粒子的宏觀磁化響應(yīng)的交流磁化率與動態(tài)特性參數(shù)(有效弛豫時間)相結(jié)合。鑒于有效弛豫時間表現(xiàn)出的溫度敏感性,利用有效弛豫時間作為中間過渡的變量,將交流磁化率與溫度信息相結(jié)合從而建立了有效的溫度測量模型。根據(jù)溫度測量模型,搭建了相應(yīng)的溫度測量裝置。通過該溫度測量裝置,驗證了該磁納米溫度測量模型的可行性。實驗結(jié)果表明,該溫度測量最大測量誤差為0.3 K,溫度誤差標準差達到0.1 K。最后,本文討論了粒徑分布與直流場等參數(shù)對溫度測量的影響�？紤]到基于磁納米粒子的濃度及溫度成像需要使用高梯度直流激勵磁場這一因素,本文分析了在高幅度激勵磁場下磁化響應(yīng)強度的變化對溫度測量的影響。該研究為進一步優(yōu)化溫度測量模型、溫度測量的精度及速度提供了理論依據(jù)。
[Abstract]:Temperature is the key parameter of tumor diagnosis and hypertherapy, and it is also an important index in the frontier cross field of modern biothermic physics and information research. For the complex biochemical environment in organisms, the magnetic nano-temperature measurement method based on the temperature sensitivity of magnetic nanoparticles is considered to be an effective non-invasive temperature measurement method. In order to meet the requirements of high precision and fast response temperature measurement system proposed by tumor hypertherapy, the existing magnetic nanometer temperature measurement methods excited by low frequency magnetic field are optimized and upgraded in this paper. The dynamic characteristics (magnetic relaxation phenomenon) of magnetic nanoparticles excited by time-varying magnetic field at medium and high frequency are studied, and a method for measuring the temperature of magnetic nanoparticles excited by time-varying magnetic field at medium and high frequency is proposed. The main contents of this paper are as follows: firstly, in order to improve the accuracy of temperature measurement, based on the existing magnetic nanotemperature measurement methods excited by low frequency time-varying magnetic field, the influence of the parameters in the model on the accuracy of temperature measurement is analyzed in this paper. The particle size of magnetic nanoparticles and the optimization method of discrete excitation magnetic field are studied and designed. The experimental results show that the temperature measurement accuracy increases with the increase of the particle size of superparamagnetic magnetic nanoparticles on the premise that the excitation magnetic field is the same. In addition, the discrete distribution of excitation magnetic field is optimized in this paper, and the optimization results show that the accuracy of temperature measurement can be improved by 30%. The optimization method can be used to measure the temperature in special environment such as cell. Secondly, in order to improve the temperature measurement speed, the dynamic characteristics (magnetic relaxation phenomenon) of magnetic nanoparticles excited by medium and high frequency time-varying magnetic field are studied in this paper. By studying the Bloch relaxation equation, the relationship between the magnetization response of magnetic nanoparticles excited by time-varying magnetic field and time is analyzed. The experimental results show that the lag phenomenon of superparamagnetic magnetic nanoparticles excited by medium and high frequency magnetic field leads to the fact that the existing temperature measurement technology under low frequency magnetic field excitation is no longer suitable for the case of medium and high frequency time-varying magnetic field excitation. Based on this, it is necessary to study the magnetic nano-temperature measurement method excited by medium and high frequency magnetic field. In order to study the measurement method of magnetic nano-temperature under medium and high frequency excitation magnetic field, the AC magnetic susceptibility describing the macroscopic magnetization response of magnetic nanoparticles is combined with the dynamic characteristic parameters (effective relaxation time) by using the Bloch relaxation equation. In view of the temperature sensitivity of the effective relaxation time, an effective temperature measurement model is established by combining the AC magnetic susceptibility with the temperature information by using the effective relaxation time as the variable of the intermediate transition. According to the temperature measurement model, the corresponding temperature measuring device is built. The feasibility of the magnetic nano-temperature measurement model is verified by the temperature measuring device. The experimental results show that the maximum measurement error of the temperature measurement is 0.3 K, and the standard deviation of the temperature error is 0.1 K. Finally, the effects of particle size distribution and DC field on temperature measurement are discussed. Considering that high gradient DC excitation magnetic field is needed for magnetic nanoparticles concentration and temperature imaging, the influence of magnetization response intensity on temperature measurement under high amplitude excitation magnetic field is analyzed in this paper. This study provides a theoretical basis for further optimizing the temperature measurement model and the accuracy and speed of temperature measurement.
【學位授予單位】：華中科技大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：R730.5;TB383.1

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