近年來近紅外光光譜以非侵入式應用於量測大腦活動時腦組織中血紅素含氧變化情形。此近紅外光光譜主要利用偵測雙波長近紅外光的光強度衰減，進而推算出組織中含氧血紅素與非含氧血紅素濃度變化。
本研究目的是藉由分頻強度調變(frequency-division intensity modulation)方式發展出一套多通道連續式近紅外光光譜應用於動物研究。此調變頻率範圍在 3.9至5.1kHz分別以弦波調變光源，此系統利用崩潰光二極體偵測器(APD)接收光訊號，再以數位IQ解調方式解調出不同通道的光訊號。
本研究結果顯示以固態假體測試不同的光源與光偵測器距離驗證光強度呈現指數性衰減變化；接著以具有特定散射係數的Intralipid溶液依序加入Ink此吸收物質形成不同吸收係數濃度，此結果亦顯示光強度呈現指數性衰減變化。在動物實驗驗證上，本系統藉由短暫的缺血性中風老鼠來驗證量測含氧血紅素與非含氧血紅素相對濃度的變化情形，可看出在缺血情況下組織的含氧血紅素會降低且非含氧血紅素的相對濃度也因此升高，當回復供血後可明顯看出含氧血紅素濃度上升，非含氧血紅素也相對下降回復到初始量測狀態。
因此，本研究提供分頻強度調變與IQ解調的方法來達到利用近紅外光光譜量測大鼠中腦部中風缺氧時的血紅素含氧程度變化量，未來可擴充成多通道近紅外光光譜系統之應用。

Near-infrared spectroscopy (NIRS) has been applied to noninvasively measure changes in the hemoglobin oxygenation state in brain activation. The concentration change of oxy- and deoxyhemoglobin can be calculated from the intensity changes of detected light at two wavelength (780nm and 830nm) based on the modified Lambert-Beer law.
Our goal is to develop a prototype continuous wave (CW) fNIRS system by using frequency division method for multichannel application in animal studies. The frequency division method is used to modulate more light sources sinusoidlly at frequencies ranging from 3.9 to 5.1 kHz. And our system utilize avalanche photodiode (APD) detector which output was separated into each modulated signal by the IQ demodulation method.
We have estimated the phantom with variable known concentrations of intralipid and ink. In the calibration validation, black ink was added to increase absorption coefficient (μa), the optical intensity was decreased linearly. In addition, we have also found that variability of the results from rat brain, the initial rate of decrease of concentration of oxy-Hb(Δ[HbO2]) is equal to the initial rate of increase of concentration of deoxy-Hb (Δ[Hb]) during reversible internal carotid artery occlusion. After reperfusion, the hemodynamic responses are significantly different between occlusion and
reperfusion, with the Δ[HbO2] being larger than baseline.
In conclusion, our prototype CW fNIRS system with multiple light intensity modulation and digital IQ demodulator technique can be a sensitive indicator to detect changes in the tissue vascular oxygenation state and hemodynamic of the brain for multichannel measurement.

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