Design And Implementation Of Function Near-infrared Spectroscopy Imaging System Based On Continuous Wave Modulation

Functional near-infrared spectroscopy is a brain imaging technique that has become increasingly popular in recent years.It can reflect changes in blood flow caused by brain activity in the human brain and monitor blood oxygen metabolism in the brain.In addition,because the low-frequency oscillation signals(0.01~0.15Hz)in blood oxygen are independent of the heartbeat signal and the respiratory signal which can can detect the slow changes in hemodynamic parameters,which can the combination of functional and nearinfrared spectroscopy imaging techniques has gradually become a hot topic.In this case,in order to facilitate the study of low-frequency oscillation signals of the human brain,a dualchannel functional near-infrared spectroscopy imaging system based on continuous wave modulation was designed.Firstly,the hardware circuit of the functional near-infrared spectroscopy imaging system was designed.For the shortcomings of the traditional continuous wave detection system,the working principle and working method of the system were designed.Based on this,the DAQ board was used as the hardware platform of the system.The performance characteristics of the light source were analyzed,the driving method of the light source was established,and the drive circuit of the light source was further designed.Explained the multiplexed hardware design idea,and completed the design of time division multiplexing circuit accordingly.The performance of the photodetector was analyzed and the type of the photoelectric conversion module was clarified,thereby achieving photoelectric conversion.The band pass filter circuit and gain amplification circuit were designed in detail.The initial processing of the signal was completed and the signal input requirements were achieved.Secondly,the system software was designed by using Labview.The design of the carrier signal was completed according to the principle of system operation.The design of the drive and acquisition control program were completed according to the mode of system operation.The demodulation principle of functional near-infrared spectroscopy imaging technology was analyzed,and digital demodulation software was designed.Aiming at the problem of tissue divergence in near-infrared spectroscopy,relevant algorithms were designed to realize the calculation of hemoglobin concentration.On this basis,the extraction of low-frequency oscillation signals in blood oxygen concentration was completed.Finally,a dual-channel functional near-infrared spectroscopy imaging system was developed,and performance verification and experimental analysis were performed.The system was compared with the ETG-4000 by using a home-made optical analog simulator to objectively evaluate the system performance.The verification of the system detection reliability was completed through the Valsalva aerobic monitoring experiment;and on top of that,combined with a multi-channel oximetry detector,a test for correlation verification of the brain and peripheral tissues was completed.