關於人體大腦活動的近紅外光譜研究中，伴隨大腦活動時，有兩種主要的光學訊號可以被發現到;分別是較緩慢的血氧濃度變化與快速的神經訊號。其中快速的神經訊號根據推測可能與神經活動有關，但是訊號較微小而且比較難去偵測的到。本研究的目的，去建立一套可以同時去測量血氧濃度變化訊號與神經活動訊號的多通道高頻近紅外光譜系統；利用高頻強度調變光源經由光纖打入物質內，延伸先前的研究將調變頻率從10 KH提升到125 MHz，再使用靈敏度高的光電倍增管偵測微弱的散射光源並將以轉化成電訊號，最後透過類比IQ解調變的方式，將高頻訊號混波，取其低頻成分經由運算得到高頻成分的振幅與相位資訊。
透過假體實驗對架設好的系統做校準的測試，而假體的成分包含具有散射特性物質的 Intralipid 與吸收特性物質的Ink溶液。在不同的變因，例如：調變頻率，光源到接收器的距離以及調配不同的溶液濃度，同時量測訊號的強度衰減與相位平移的變化來驗證系統。。在未來本系統可進一步應用在動物與細胞的研究上，用以檢測神經活動地情形。

Two major types of optical signals following functional brain activation can be observed, the slow hemodynamic signal and the fast neuronal signal. The fast neuronal signal is supposedly related to neuronal activity, but its intensity is small and difficult to detect. The aim of this study was to set up a multi-channel high frequency fNIRS system for detecting the slow hemodynamic as well as the fast neuronal signals. We utilized high-frequency intensity-modulated light source through optical fiber to illuminate the medium. The modulated frequency was changed from 10 KHz up to 125 MHz used in our previous study. Instead of photodiode, high sensitivity photomultiplier tube (PMT) with Peltier cooling system was applied to detect scattering light and transform optical signal into electrical signal. The low frequency I and Q components from mixed signals were acquired from the analog in-phase and quadrature (IQ) demodulator for deriving the amplitude and phase information.
The designed high frequency fINRS system was first calibrated in phantom in which the intralipid was used as scatter for varied amount of ink absorber. Under the phantom setup, we varied the modulated frequencies, the source-to-detector distance, and the concentration of intralipid-ink solution for validation purposes. Our observations on the amplitude attenuation and phase shift coincided with those of previous studies. The designed high frequency fNIRS system could be applied to brain activities of animal experiments and neuronal activities of cultured neurons in future studies.

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