以序列切換式非對稱刺激波形實現殘餘電荷誤差比小於0.1%之電流式神經刺激器

Using sequential switching asymmetric stimulating waveforms to implement a current-mode neuron stimulator with residual charge mismatch percentage less than 0.1%

陳俊廷(Chen, Jyun Ting)

指導教授 ： 鄭桂忠

國立清華大學/電機資訊學院/電機工程學系/碩士(2015年)

摘要

近幾年來生醫電子領域已逐漸被人們重視並投入發展。已有許多研究指出功能性電刺激可用來治療許多神經性疾病、恢復部分器官功能、修補因神經受損造成的殘疾…等可為人們帶來更健康、更方便的生活。而這種功能性電刺激即是由刺激電路所產生的。
一般而言，在許多的植入式裝置裡，刺激電路由於是最靠近神經的IC電路，所以在設計上對於安全的需求是最為重視的。而在安全上通常是以「經過刺激後，殘留在電極/神經上的殘餘電荷」這個指標為基本要求。我們希望此值能越低越好，以避免刺激器後端的電極陣列在長期運作後產生像是電解的質變，進而傷害到神經；如同我們對於神經的基本生理認知，神經需要足夠的閥值電荷才能被刺激。而已有研究指出刺激器若能輸出「非對稱式刺激波形」這種特殊的功能性電刺激的話，有助於壓低神經刺激時所需要的閥值電荷，並可使刺激器的能量利用率及運作時間皆有進步；然而在輸出非對稱式波形下，又要能夠達到夠低的殘餘電荷，在設計電路角度上是非常困難的。
本論文即是觀察到了上面的設計困境，並以過去文獻的方法為基礎改進，成功地達到了能在輸出非對稱式波形的情況下同時兼顧低殘餘最後電荷。在模擬上達到了能在輸出400μA的非對稱式刺激波形下，其殘餘電荷佔總輸出電荷誤差比降低至0.1％以下。

關鍵字

神經刺激電路 ； 功能性電刺激 ； 非對稱式波形 ； 低殘餘電荷

並列摘要

Bio-medical field has drawn more and more attention in recent years. Functional electrical stimulation (FES) has been researched and applied to treat neuron disease, repair the physiological function of patients suffering from neuron damage. The stimulator is very close to neuron in all implantable devices, so safety is the critical point. Usually, residual charge on electrode/neuron interface after once stimulation is estimated as safety standard. We wish the residual charge can be reduced as low as possible. Because lower residual charge means the electrode electrolysis probability is smaller.
Besides, some researches have proven that the stimulator with asymmetric stimulation output waveform can reduce neuron stimulation threshold charge effectively. However, stimulator with asymmetric output waveform is hard to reduce residual charge because of its difficult calibration through circuit.
According to above design hard point, we use an improved current source control signal called sequential switching signal (S.S signal) to achieve lower residual charge when transferring asymmetric waveform. The stimulator has been fabricated using TSMC 0.18μm technology. Simulation result shows that stimulation current is up to 400μA and its residual charge mismatch percentage is less than 0.1%.

並列關鍵字

stimulator circuit ； Functional electrical stimulation ； asymmetric waveform ； low residual charge

參考文獻

[1] P. Berruecos, "Cochlear Implants: An International Perspective – Latin American Countries and Spain: Implantes Cocleares: Una Perspectiva Internacional - América Latina y Espana," Audiology, vol. 39, pp. 221-225, 2000/01/01 2000.

[2] M. D. Eisen, "Djourno, Eyries, and the first implanted electrical neural stimulator to restore hearing," Otol Neurotol, vol. 24, pp. 500-6, May 2003.

[3] K. Vermeire, J. P. L. Brokx, P. H. Van de Heyning, E. Cochet, and H. Carpentier, "Bilateral cochlear implantation in children," International Journal of Pediatric Otorhinolaryngology, vol. 67, pp. 67-70.

[4] E. Offeciers, C. Morera, J. Muller, A. Huarte, J. Shallop, and L. Cavalle, "International consensus on bilateral cochlear implants and bimodal stimulation," Acta Otolaryngol, vol. 125, pp. 918-9, Sep 2005.

[5] J. Reefhuis, M. A. Honein, C. G. Whitney, S. Chamany, E. A. Mann, K. R. Biernath, et al., "Risk of Bacterial Meningitis in Children with Cochlear Implants," New England Journal of Medicine, vol. 349, pp. 435-445, 2003.