超音波無線神經電刺激器

Abstract

本研究的目的在於利用超音波來代替傳統射頻電磁波(radio frequency electromagnetic wave)，在人體內進行訊號傳輸的探討和測量。由於超音波相對射頻電磁波而言，超音波本身能夠輕易的進行聚焦設計，而聚焦點設計的用意，在於人體傳輸的路徑上並不會因為能量過大而使得溫度上升，導致人體組織的損壞破損，更重要的是，超音波傳導的方式為機械波，因此不會有射頻電磁波輻射汙染的疑慮，適合進行人體內的訊號傳輸。 由於目前利用射頻電磁波做為進行人體能量傳輸的電刺激器，效率還是依舊太低[1]，針對此缺點，本論文中，我們提出一個超音波無線電刺激器的實驗架構，以解決人體中的電刺激器能量不足的問題，目前在人體安全規範下，6(mm)感測器在能量接收最大可達15.91(mW)。而另一方面我們可以藉由超音波訊號負載資料訊號，來控制人體中的電刺激器能夠依照指示來工作，利用目前所設計的編碼，藉由電腦模擬測試獲得資料錯誤率在10-6以下，我們可以證明利用超音波來傳送資料是可行的。針對超音波在人體組織的傳遞上，在能量傳輸方面，我們設計的超音波感測器必須與後端電路的電阻抗做匹配，才可達到能量傳輸效率的最佳化。而在整體能量傳輸的過程中，我們分別進行每一層級的電路架構做能量損耗的測試，藉由這些測試，我們可以針對每一層級的能量損耗情形做適當的改進與改善。 本研究在資料編碼中，我們針對超音波的特性分別提出了Amplitude Shift Keying with Carrier (ASK-Carrier)和Frequency Shift Keying with Pulse Width Modulation (FSK-PWM)及傳統PSK (Phase shift keying)的編碼方式來進行資料傳輸，並且我們設計了實驗架構來模擬比較這三者的資料傳輸的錯誤率，以提供未來超音波在編碼設計上的依據。

This study investigates the communication in vivo, which aims to use the ultrasound instead of the RF-EM wave (radio-frequency electromagnetic wave). As opposed to RF-EM wave, the ultrasound is easier on focus design than RF-EM, the focus design can prevent the damage of tissue on transmission path when concentrates the energy on the object, and the most important thing is that the ultrasound is a mechanical wave, there will be no electromagnetic radiation contamination, which would be more suitable than RF-EM on the communication in vivo. In response to the inefficiency of RF-EM electrical-stimulator on the communication in vivo [1], we proposes a structure of wireless ultrasonic electrical-stimulator to solve the lack of energy with implanted electrical-stimulator; under the safety regulations in the human body, the 6mm sensor can receive at most 15.91 mW. On the other hand, we can load the instructions on the ultrasound signal to control implanted electrical-stimulator, in our designed coding, the BER (bit error rate) of the data transmission is below 10-6 with the computer simulation, and we can demonstrate that the communication in vivo by using ultrasound is feasible. On power transmission, in order to achieve the optimal energy transfer efficiency, our ultrasonic sensor design must match the electrical impedance of stimulator circuit. And in process of overall energy transmission, we measure each level of the stimulator circuit structure of energy consumption, and then we can make an appropriate improvement to increase the efficiency on energy transfer by these tests. In this study, we design and measure the bit error rate of Amplitude Shift Keying with Carrier (ASK-Carrier) and Frequency Shift Keying with Pulse Width Modulation (FSK-PWM), and we also measure the BER of traditional coding: PSK (Phase shift keying), by comparing these coding, we could provide the basis on coding design in the future.