新型开放式超导MRI主磁体设计

发布时间：2018-02-25 02:01

本文关键词： 磁共振成像多二次径向基函数超导表面响应模型进化策略　出处：《沈阳工业大学》2012年硕士论文　论文类型：学位论文

【摘要】：磁共振成像(MRI,Magnetic Resonance Imaging)技术是目前最有价值、最有发展前景的医学诊断技术之一。MRI设备是一种高端医疗诊断设备,其磁体结构分为永磁型、常导型和超导型三种。在我国,由于稀土永磁资源丰富,使得永磁型MRI的价格相对低廉,而且其磁体结构开放性好,所以永磁型MRI广泛应用于临床。但是,近年来由于国家对稀土资源的限制政策,永磁低场MRI的价格优势正逐步消失,这使得超导型MRI又重新走入人们的视线。传统超导型MRI装置通常采用螺线管式磁体结构,其成像空间为一个圆柱腔体,开放度低。为了提高超导MRI磁体结构的开放度,本文提出了一种新型开放式超导型MRI磁体结构。提出的新型超导MRI设备的磁体形式参照了永磁MRI的开放式结构,而主磁场则是由超导线圈产生。为了实现其成像区的高磁场强度、高磁场均匀度等设计目标,本文研究了一种全局优化算法。在优化算法执行过程中,首先,利用正交试验法从初始设计变量中确定出影响磁体性能指标的关键设计变量;然后,在变量空间内,利用拉丁超立方采样策略获得均匀分布的空间采样数据;并利用表面响应模型中多二次径向基函数近似模拟优化目标。同时,讨论了表面响应模型中形状参数的选取方法;最后,使用进化策略寻求表面响应模型的全局最优解。为了验证上述算法的有效性,本文选取了解析函数进行测试。并对国际公认的验证优化算法有效性的TEAM标准问题22进行了计算,对比分析了计算结果。最后,将上述优化算法应用于开放式超导MRI主磁体结构的优化设计。以磁体极面形状为优化对象,完成了所提出的超导MRI磁体结构的最佳尺寸设计,获得了一种高场强、高均匀度的主磁体结构。
[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.

【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R318.6

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