Development Of A Portable Continuous-wave NIR Instrument For Brain Function Imaging

Non-invasive in-vivo measurement is one of the greatest contributions provided by modern medical signal detection technology. Attributing to non-invasive method, NIRS has been developed rapidly in recent decades. The system based upon NIRS has such advantages as light weight, compact size, low power consumption and cost so that it will have a wide application in brain function research field.In this paper, the basic principle of NIRS was introduced and also a new type of portable 16-channel brain function imager using continuous-wave has been designed. The system adopted a palmed DAQ using USB interface and other application specific integrated circuits (ASIC) products as the detector, light source and its drive circuit, which made the net weight within 1Kg. The probe was so flexible that was easy to belt on and made good attachment to skin. The detection area was 4.4 cm×15cm, which can cover the DLPFC and partial VLPFC. The maximum temporal resolution of the instrument was 100ms which was adequate to identify transient response of hemodynamic changes including the oxy/deoxy-hemoglobin and blood volume.In order to realize the signal collection and the display of changes of HbO2, Hb and Blood volume, the software for this brain function imaging instrument has been developed. The object-oriented programming thinking, which made data centered in software structure, impenetrate the procedure of the system software development. This program was constructed on Visual C++6.0 platform. The"Doc-View"structure was the core framework of the whole application software. Multi-thread technique made the data-collection and data-display modules work in parallel with each other synchronously.By means of performance test, in-vitro model experiment, the system property and accuracy of measurement was validated. The ultimate in-vivo experiment made use of the Valsalva maneuver inducing the cerebral blood flow (CBF) stress adjustment, the results of which was in accordance with the physiology knowledge, demonstrating the feasibility of in-vivo measurement.