Optical non-invasive flowmetry without lasers and coherent light

Laser Doppler Flowmetry (LDF) and other optical technique to measure a blood flow in tissues noninvasively (in vivo) are well-known today. Meanwhile, in spite of more than 40-year history, they do not have applications in real clinical practice yet. This situation could be a consequence of incorrect understanding of the physical basics of these methods and, accordingly, of insufficient hardware design, software algorithms, as well as of erroneous interpretation of the data measured. The basic theory of physical principles of LDF is the model developed by R.Bonner and R.Nossal in 1980. However, it does not describe many phenomena, low-frequency fluctuations of optical fields due to a variable blood content in a tissue diagnostic volume, for example. In this study, we assumed that the low-frequency part of the power spectrum could provide the same information about the blood flow as the middle- and high-frequency parts provide it in LDF. Moreover, we proposed the use of coherent light source could be avoided in this case. We have developed a much simpler and low-cost LED-based prototype and confirmed our assumptions in experiments. Thus, we proposed a new technique to build simple and economic optical diagnostic tool to evaluate a blood flow in tissues.