Research Of A Cerebral Oxygenation Monitoring Technology Using Near-Infrared Spectroscopy

Human brain as the body's central nervous organ dominates and commands all the physiological activities of the human body. Both blood flow and oxygen consumption in human brain tissue is in large quantity. As a particular region in the brain activates, its local blood volume accordingly increases. The increased volume reflects the degree of activation. Blood volume changes in the brain can be used as an indicator of brain function activities. To monitor cerebral blood oxygenation changes by the technology of near infrared spectroscopy (hereafter NIRS) has many advantages such as non-invasion, real time, continuity, high res-olution of time, cheapness and simplicity of operation, thus making it possible to be widely applied in the areas of exploring brain function activities, positioning regional brain function and brain protection in clinical practice.In this paper, the optical properties of biological tissue and basic principle regarding biological tissue optics is introduces. On the basis of revising Lambert - Beer law, the research combines it with spetially-resolved spectroscopy theory, and then develops a multi-wavelength and multi-channel NIRS monitoring sys-tem for detecting cerebral blood oxygenation.The monitoring system developed by our team includes sensors, analog cir-cuits, digital circuits and other system modules such as host computer. Sensor probe equipped with integrated multi-wavelength LED as its light source, low-noise, high-gain OPT101 as its light detector. The hardware circuit with MCU C8051F020 as its core, controls the light source driver chip, which also functions in A/D acquisition, data processing, liquid crystal display, button con-trols, serial communication. And the host computer control system is mainly re-sponsible for serial communication, data storage, real-time display of oxygen sa-turationA series of experiments and tests for the system has been carried out. In ex-periment of vitro tissue phantom, solid tissue phantoms are produced with whose optical properties close to human tissue. The stability and effectiveness of the system get proved through the conduct of single imitated tissue modeling expe-riment. In the multi-layer imitated tissue modeling experiment, our team has si-mulated the multi-layer structure of human head, and explored the impact of out- er layer of brain tissue on the results of cerebral blood oxygenation, thus provid-ing the theoretical basis for the correction of measurement results in the moni-toring system. Human forearm block experimental results demonstrate that the changes of oxygen saturation detected by this system show the same trend with blood oxygen saturation changes in the tissue. Finally, experimental results also attest that, the changes in optical density detected by the system can reflect changes in cerebral blood volume, thereby can monitor the functional activities of particular regions in the brain. The experimental results certify the method of NIS oxygen monitoring system has great prospects in researching the cognitive activ-ities of the human brain.