Occlusion spectroscopy as a new paradigm for non-invasive blood measurements

We prove experimentally that RBC aggregation is among the major factors affecting time evolution of light transmission in both the normal situation of pulsatile blood flow and the situation of over-systolic vessel occlusion. Optical transmissions of tissue in-vivo have been measured in red/near-infrared region. Sudden blood flow cessation causes the light transmission rising. For certain wavelengths range this growth becomes non-monotonic. The correspondence between in-vivo measurements and the theoretical simulations is reached if we attribute the transmission growth to the change of average size of scatterers. The most important blood parameters such as hemoglobin, glucose, oxygen saturation, etc., influence the transmission growth following over-systolic occlusion, and, therefore, may be extracted from the detailed analysis of the time evolution of optical transmission. It forms a basis for new kind of non-invasive measurements, i.e.: occlusion spectroscopy. The results of in-vivo clinical trials are presented for glucose and hemoglobin.