Methodology on optical topographic mapping based on multi-wavelength lock-in detection

Optical topographical imaging has been regarded as the most beneficial supplement to the other established methods used in the functional mapping of human cerebral cortex. Also, quantifying the changes in cerebral oxygenations plays a great role in clinical diagnosis and treatment. Now the existing optical topographic mapping system is too expensive to be popularized. Thus, a dual-wavelength optical topography system with low cost and simple structure is developed, aiming at quantifying the hemoglobin concentration changes in shallow tissue regions using the optode array. In this system, two laser beams with different wavelengths are combined and the signals are simultaneously detected using a digital lock-in technique. By applying the modified Beer-Lambert law to each adjacent sourcedetector pairs, the changes of hemoglobin concentration in the cerebral cortex caused by physiological or psychological activities can be calculated.