本文關(guān)鍵詞： 磁共振成像 多二次徑向基函數(shù) 超導(dǎo) 表面響應(yīng)模型 進(jìn)化策略　出處：《沈陽工業(yè)大學(xué)》2012年碩士論文　論文類型：學(xué)位論文

【摘要】：磁共振成像(MRI,Magnetic Resonance Imaging)技術(shù)是目前最有價值、最有發(fā)展前景的醫(yī)學(xué)診斷技術(shù)之一。MRI設(shè)備是一種高端醫(yī)療診斷設(shè)備,其磁體結(jié)構(gòu)分為永磁型、常導(dǎo)型和超導(dǎo)型三種。在我國,由于稀土永磁資源豐富,使得永磁型MRI的價格相對低廉,而且其磁體結(jié)構(gòu)開放性好,所以永磁型MRI廣泛應(yīng)用于臨床。但是,近年來由于國家對稀土資源的限制政策,永磁低場MRI的價格優(yōu)勢正逐步消失,這使得超導(dǎo)型MRI又重新走入人們的視線。傳統(tǒng)超導(dǎo)型MRI裝置通常采用螺線管式磁體結(jié)構(gòu),其成像空間為一個圓柱腔體,開放度低。 為了提高超導(dǎo)MRI磁體結(jié)構(gòu)的開放度,本文提出了一種新型開放式超導(dǎo)型MRI磁體結(jié)構(gòu)。提出的新型超導(dǎo)MRI設(shè)備的磁體形式參照了永磁MRI的開放式結(jié)構(gòu),而主磁場則是由超導(dǎo)線圈產(chǎn)生。 為了實現(xiàn)其成像區(qū)的高磁場強度、高磁場均勻度等設(shè)計目標(biāo),本文研究了一種全局優(yōu)化算法。在優(yōu)化算法執(zhí)行過程中,首先,利用正交試驗法從初始設(shè)計變量中確定出影響磁體性能指標(biāo)的關(guān)鍵設(shè)計變量;然后,在變量空間內(nèi),利用拉丁超立方采樣策略獲得均勻分布的空間采樣數(shù)據(jù);并利用表面響應(yīng)模型中多二次徑向基函數(shù)近似模擬優(yōu)化目標(biāo)。同時,討論了表面響應(yīng)模型中形狀參數(shù)的選取方法;最后,使用進(jìn)化策略尋求表面響應(yīng)模型的全局最優(yōu)解。 為了驗證上述算法的有效性,本文選取了解析函數(shù)進(jìn)行測試。并對國際公認(rèn)的驗證優(yōu)化算法有效性的TEAM標(biāo)準(zhǔn)問題22進(jìn)行了計算,對比分析了計算結(jié)果。 最后,將上述優(yōu)化算法應(yīng)用于開放式超導(dǎo)MRI主磁體結(jié)構(gòu)的優(yōu)化設(shè)計。以磁體極面形狀為優(yōu)化對象,完成了所提出的超導(dǎo)MRI磁體結(jié)構(gòu)的最佳尺寸設(shè)計,獲得了一種高場強、高均勻度的主磁體結(jié)構(gòu)。
[Abstract]:Magnetic resonance imaging (MRI, Magnetic Resonance Imaging) technology is currently one of the most valuable medical diagnostic technology.MRI equipment, the most promising is a high-end medical diagnostic equipment, the magnet structure is divided into permanent magnet type, regular and super conducting type three. In our country, because of abundant resources of rare earth permanent magnet the permanent magnet type MRI, the price is relatively low, but also of its open magnet structure, so the permanent magnet type MRI is widely used in clinic. However, in recent years due to restrictions on rare earth permanent magnet low field MRI countries, the price advantage is gradually disappearing, which makes the superconducting MRI again into people's the line of sight. The traditional superconducting MRI device usually adopts a solenoid magnet structure, the imaging space is a cylindrical cavity with low degree of openness.
In order to improve the openness of superconducting MRI magnet, a new superconducting MRI magnet structure is presented in this paper. The magnet form of the new superconducting MRI device refers to the open structure of permanent magnet MRI, while the main magnetic field is generated by superconducting coils.
In order to achieve high magnetic field intensity in the imaging region, high uniformity of magnetic field and other design goals, this paper presents a global optimization algorithm. The optimization algorithm in the implementation process, first, using the method of orthogonal experiment from the initial design variables determine the key performance index of the magnet design variables; then, in the variable space. To obtain a uniform spatial distribution of sampling data using the Latin hypercube sampling strategy; and using the response surface model of radial basis function to approximate time two optimization objectives. At the same time, discussed the response surface shape parameters in the model selection method; finally, using evolutionary strategy to seek the global optimal solution of the RSM.
In order to verify the effectiveness of the algorithm, we choose the analytic function to test it. We also calculate the TEAM standard 22, which is internationally recognized to verify the effectiveness of the optimization algorithm, and compare the calculation results.
Finally, the optimization design of the optimization algorithm is applied to open superconducting MRI magnet structure. The magnet pole shape as the optimization object, completed the design of optimum size of superconducting MRI magnet of the proposed structure, obtained a high field magnet structure, high uniformity.

【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：R318.6

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本文編號：1532555