Design of a Portable Near Infra-Red Spectroscopy System for Tissue Oxygenation Measurement

A portable near-infrared spectroscopy (NIRS) system has been developed to provide real-time temporal and spatial information about the cutaneous tissue response to physiological stimulation. We describe the use of embedded technology, to realize the miniaturization of the NIRS system. On the platform of Windows CE and S3C2410 microprocessor, the paper introduces the process of designing and executing the equipment testing system from the viewpoints of both hardware and software. A detailed analysis of the implementation for tissue oxygenation measurement is described. The instrument design allows the collection of optical spectrum data with the use of a graphical user interface (GUI) based on a touch screen by using advanced ARM embedded techniques, making use of the abundant features of the ARM processor. The signal output is displayed as an image of oxy-haemoglobin and deoxy-haemoglobin concentration ([HbO₂], [HHb]) changes at a frame rate of 40 Hz. Experiments have been conducted on phantoms to determine the sensitivity of the system. The system has been tested in volunteers by imaging changes in forearm muscle oxygenation, following blood pressure cuff occlusion to obtain typical [HHb] and [HbO₂] plots. From the results of the experiments, the equipment is not only user-friendly but also portable, reliable and cost effective beyond the traditional equipment based on a PC.