【摘要】：經(jīng)顱磁刺激（TMS）是一種作用于中樞神經(jīng)系統(tǒng)的非侵入式刺激技術，它利用時變磁場，在目標區(qū)域中感應出感生電場，從而改變細胞膜內外電位差達到引起組織細胞興奮地目的。由于顱骨對磁場具有通透性，磁場能直接穿過頭皮和顱骨刺激深部神經(jīng)組織。相比于傳統(tǒng)的電極刺激方式，磁刺激具有更大的優(yōu)勢，其無創(chuàng)傷性、安全性、方便性、易于重復操作等優(yōu)點，在臨床上的應用研究越來越廣泛。但現(xiàn)有的系統(tǒng)體積龐大、成本過高、刺激線圈磁聚焦效果差等缺點，限制了經(jīng)顱磁刺激在臨床上的應用，這些都是經(jīng)顱磁刺激技術待解決的問題。 為了實現(xiàn)磁聚焦，本文構建了分別包括8個子線圈和20個子線圈的圓環(huán)面線圈陣列模型。因影響磁聚焦的因素很多，解空間較大，本文提出利用群集智能優(yōu)化算法優(yōu)化線圈模型的方法。在基本粒子群優(yōu)化算法和標準遺傳優(yōu)化算法的基礎上，提出改進的混合遺傳-粒子群算法，并用測試函數(shù)測試算法收斂于全局最優(yōu)解的效率和成功率。結果表明，改進后的混合遺傳-粒子群算法性能良好，在收斂速度和收斂率上有明顯的優(yōu)勢。最后用該算法對影響線圈陣列模型磁聚焦性的各種參數(shù)進行優(yōu)化求解，并將優(yōu)化結果與傳統(tǒng)的8字形線圈比較，結果顯示，兩種線圈陣列模型均有良好的磁聚焦性，20個子線圈的圓環(huán)面線圈模型基本上實現(xiàn)了點聚焦。 另一方面，本文詳細介紹了經(jīng)顱磁刺激的生理基礎和物理學原理、經(jīng)顱磁刺激激勵源系統(tǒng)的工作機理，對激勵系統(tǒng)中影響感應磁場強度的因素進行分析，并得出結論，刺激線圈中電流的變化率和電流大小直接影響感應磁場強度和感生電場大小。在此基礎上設計并實現(xiàn)了實際硬件電路，包括高壓主回路、整流濾波電路、控制回路等，詳細分析了電路中各參數(shù)對系統(tǒng)安全性、穩(wěn)定性、磁場能量的影響，并提出改進方案。最后在180V電源電壓供電情況下，，刺激線圈中獲得峰值為320A，脈寬400us的脈沖電流，電流變化速度快，實現(xiàn)了脈沖大電流的產(chǎn)生。對獲得的電流進行頻譜分析，其主要能量集中在0-20kHz。本文對目前經(jīng)顱磁刺激系統(tǒng)的缺點提出了改進的方案，對經(jīng)顱磁刺激技術的發(fā)展有一定的指導作用。
[Abstract]:Transcranial magnetic stimulation (TMS) is a non-invasive stimulation technique acting on the central nervous system. It uses time-varying magnetic field and induces induced electric field in the target region, thus changing the potential difference between the cell membrane and the cell membrane to induce excitatory effect of tissue and cell. Because of the permeability of skull to magnetic field, magnetic field can directly penetrate the scalp and skull to stimulate deep nerve tissue. Compared with the traditional electrode stimulation, magnetic stimulation has more advantages, such as non-invasive, safe, convenient, easy to repeat, and so on. However, the large volume, high cost and poor magnetic focusing effect of the current system limit the clinical application of transcranial magnetic stimulation, which are the problems to be solved by transcranial magnetic stimulation. In order to realize magnetic focusing, a toroidal coil array model including 8 subcoils and 20 subcoils is constructed in this paper. Because there are many factors affecting magnetic focusing and the solution space is large, a method of optimizing coil model by cluster intelligence optimization algorithm is proposed in this paper. Based on the basic particle swarm optimization algorithm and the standard genetic optimization algorithm, an improved hybrid genetic particle swarm optimization algorithm is proposed. The efficiency and success rate of the algorithm converging to the global optimal solution are tested by the test function. The results show that the improved hybrid genetic particle swarm optimization algorithm has good performance and has obvious advantages in convergence speed and convergence rate. Finally, the algorithm is used to optimize the parameters that affect the magnetic focusing of the coil array model, and the optimization results are compared with the traditional 8-shaped coil. The results show that, Both kinds of coil array models have good magnetic focusing. The toroidal coil model of 20 subcoils basically realizes point focusing. On the other hand, the physiological basis and physics principle of transcranial magnetic stimulation and the working mechanism of transcranial magnetic stimulation source system are introduced in detail. The factors influencing the magnetic field intensity in the excitation system are analyzed, and the conclusion is drawn. The rate of change of the current and the magnitude of the current in the stimulus coil directly affect the induced magnetic field intensity and the induced electric field. On this basis, a practical hardware circuit is designed and implemented, including high voltage main circuit, rectifier filter circuit, control circuit and so on. The effects of various parameters in the circuit on system security, stability and magnetic field energy are analyzed in detail, and an improved scheme is put forward. Finally, under the condition of 180 V power supply, the pulse current with peak value of 320A and pulse width 400us is obtained in the stimulus coil. The speed of current change is fast, and the large pulse current is generated. The main energy of the obtained current is focused on 0-20 kHz. In this paper, an improved scheme is proposed for the shortcomings of transcranial magnetic stimulation system, which can guide the development of transcranial magnetic stimulation technology.
【學位授予單位】：成都信息工程學院
【學位級別】：碩士
【學位授予年份】：2012
【分類號】：R312;TP18

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