功能性近紅外線光譜是一相當有潛力的生醫光電的功能性影像方法，用來觀察細胞與組織中的光學特性。相比較於其他非侵入式或侵入極小範圍的神經影像技術說來，功能性近紅外線光譜系統除了具有可攜性高、價格便宜及無輻射等好處之外，同時又兼具良好的時間與空間解析度。本研究之目的是利用頻域（frequency-domain）方式發展一套單頻道的功能性近紅外線光譜系統，並建立假體設計以及在缺血性中風老鼠實驗上來驗證此發展完成之系統驗證。本系統光源部分為兩個不同波長（780 nm, 830 nm）的雷射二極體組成，並由10 kHz固定電流源來驅動與頻率5 Hz的開關交替切換光源。而系統接收部分由高靈敏度接收器轉換光訊號的輸出並由數位IQ來解調出振幅與相位參數。

　　在系統完成後利用假體設計來做校準動作，其中包含具散射物質之Intralipid與吸收物質之Ink溶液。對光源進行LIV曲線之量測來確定所操作之雷射光源的範圍，進一步利用調配不同的溶液濃度來觀察最有效之光源與接收器距離，接著應用本系統來探討在動物實驗進行中的含氧血紅素與非含氧血紅素的濃度變化。本研究的缺血性中風老鼠是利用3VO之技術阻斷中間腦動脈血管並觀察由此系統量測時間過程中的缺血性的變化情形。由本系統量測之訊號結果呈現出在腦部損傷側血流量降低並且在中間區域產生顯著之變化量。藉著利用不同波長所量測之光吸收量，在組織氧化作用中可以連續的被量測出其變化情形。未來本系統進一步設計成多頻道之感測探頭結合single-unit recording成為一可實行之儀器來研究關於神經病學疾病之腦部活動情形。

　　Functional near infrared spectroscopy (fNIRS) is a promising biophotonic functional imaging method to observe the optical properties of cells or tissues. Compared to other neuroimaging techniques, fNIRS is portable, affordable, non-radiative, and in good spatial-temporal resolution. The aims of this study were to develop a single-channel fNIRS system by using frequency-domain method and to validate the developed fNIRS on phantom as well as on ischemic stroke rats. Two laser diodes with wavelengths of 780 nm and 830 nm were modulated at 10 kHz carryier frequency and driven by constant current alternately switching at 5 Hz between two sources.. The optical output of high sensitivity photo detector was demodulated to extract amplitude and phase information by using digital in-phase and quadrature demodulator.

　　The designed fNIRS was first calibrated in phantom study which consisted of Intralipid scatter and ink absorber. The light-intensity-voltage (LIV) curve was first to check the operation ranges of laser sources and was further to observe the effective source-detector distance by varying concentration of scatter and absorber. Later, the fNIRS was applied to investigate the concentration changes of oxy-hemoglobin in blood with stroke animal model study. The stroke rats were induced by the occlusion of middle cerebral artery combined the techniques of three-vessel occlusion to observe the time-course changes of ischemia by using fNIRS system. Our results showed that the reduction in blood flow at middle regions of lesion side were evident from the signals detected by our fNIRS system. By measuring the changes in light absorption at different wavelengths, tissue oxygenation can be measured continuously. Further development of the system with multichannel sensor probe with single-unit recording would be a viable device for studying the brain activity of neurological disorders.

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