週期性脈衝磁場裝置與生物體場效應分析

Abstract

一般在醫學研究上所使用的電刺激器是利用植入與電擊接觸的方式來達到實驗效果，但是採用其方式會造成植入時的風險及耗時，亦會造成電力使用上的危險。因此，我們開發一個週期性脈衝磁場電路應用於生物體之裝置，以非接觸式、非侵入方式，利用時變磁場產生的感應電流來驅動生理反應，此技術稱為週期性經顱磁場刺激(rTMS)。未來發展將應用在神經臨床上的治療，如癲癇、阿茲海默症與憂鬱症等，取代開刀、植入方式裝取電極，以線圈所產生之感應電流的方式能避免植入裝置的風險，並且感應電流打到之深度是可藉由裝置提供的強度所調整，達到有效率刺激，使神經分泌更多神經興奮物質等，達到神經活化、興奮之效果，對未來神經臨床上的研究是一大福音。 本篇主要探討經顱磁場刺激器之電路設計及其感應電流對於小鼠的心律變化，主軸探討其裝置所能產生之最大感應電流值的參數調控以及不同頻率下(10~80Hz)磁場刺激所產生的感應電流對於小鼠的心跳速率之影響。實驗數據皆指出藉由週期性經顱磁場刺激可產生感應電流驅動神經系統，藉而改變其心律功能，使其心跳速率下降。其中20Hz 刺激效果為最顯著，RR-interval 從117.16ms 上升至185.88ms，並以模擬軟體量化出感應電流值的大小，其值為25.4A/m2。

We developed repetitive pulsed magnetic field device and investigated the effects of repetitive magnetic stimulation on nerve fibers and functions of heart. A circular coil (inner diameter = 15 mm, outer diameter = 54 mm) is used in the experiments. Stimulus conditions are: peak magnetic field= 0.2 Telsa (at the center of the coil), and magnetically induced currents density in mice = 25.4 A/m2. The coil was placed above mouse head and continuously stimulated for 1 minute with frequencies from 10 to 80Hz. ECGs before and after stimulation were recorded and analyzed for the change in RR-interval in 10 mice. The most pronounced RR prolonging effect at 20Hz stimulation, which caused the average RR-interval to increase from 117.16ms to 185.88ms. The vagus nerves stimulation study shows a significant heart rate decrease due to the application of magnetic stimulation. These results indicate that the heart functions might be activated by repetitive magnetic stimulation exposure, resulting in a heart rate decrease. In this thesis, we proposed rTMS circuit design and investigated effects of rTMS on mouse heart rhythm via nerves. To confirm the validity of our method, we performed a computer simulation of the eddy current distribution using a finite element method.