雙通道非侵入式近紅外光譜儀腦訊號量測系統實現

Abstract

本論文利用帶氧與去氧血紅素對於不同波長之近紅外光吸收率不同來換算出組織血流的反應。主旨在實現一套雙通道近紅外光譜儀量測腦部生理訊號的系統，開發出一套比坊間市售儀器更簡單的系統架構以及更小的體積與較低廉的價格的系統。本系統使用發光二極體光源與感光二極體感測器，對人體組織發射與接收光源，透過類比訊號處理電路，並利用可程式邏輯陣列(FPGA)當作控制核心，控制脈衝寬度調變光源，實現分光架構與自動光強度校正。設計互動式軟體介面，建立手部血流阻斷實驗，驗證系統與演算法可行性，並藉由閉氣實驗驗證腦部血氧變化量測的正確性。接著將本系統與市售儀器(Hitachi ETG-4000)量測相同任務來進行比較，可得知在非使用Hitachi系統特定實驗的情形下，本系統在多次疊加實驗結果皆優於Hitachi。最後進行相關文獻所使用之系統比較，比較結果可得知本系統有完整實驗進行系統可行性驗證，在光源使用與分光架構較為簡便。

This study aims a simpler near-infaraed spectroscopy (NIRS) system with smaller and lower cost than commercial instrument. To detect the hemodynamic response of oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) in human tissue based on the different absorption of near-infrared light wavelengths, this system used cheap light emitted diodes (LEDs) photodiodes (PDs) as the light source and detector, respectively. For peripheral Interface control, FPGA was utilized to control the pulse width modulation (PWM) for LEDs to generate various density of light source. The light distributor for red and infrared light and the automatic power calibration in this system were implemented by analog signal processing circuits and controlled by the FPGA. This study designed an interactive brain computer interface (BCI) with the arterial occlusion experiments to test the feasibility, and then verified the system and its algorithm with breath-hold experiments. In the experiment results, the proposed system has better hemodynamic response then ETG-4000, an extremely expensive NIRS system designed by Hitachi Medical Corporation. Finally, compared with other related NIRS systems, the light source and light distributor architecture of the proposed system is more easily and simply to implement, and this study has proved the feasibility of series of experiments.