This Spotlight reviews non-invasive optical methods to determine the blood flow velocity in microcirculation, with an emphasis on the most recent developments, that may be routinely applied in cellular biology laboratories. The methods covered in this book include both scanning and whole-field optical imaging techniques based on endogenous or exogenous (fluorescent) contrast agents for plasma and red-blood-cell visualization, such as laser Doppler velocimetry, laser speckle contrast imaging, diffuse correlation spectroscopy, particle image velocimetry, and two-photon microscopy. Several methods have been developed to quantify the blood flow velocity within microvessels by exploiting the cross-correlation concept applied to optical scanning microscopes: dual-foci cross-correlation, spatio-temporal image correlation spectroscopy, line-scanning techniques, and a recently developed single raster-scanned xy-image technique (FLICS). The basic operational principles, the advantages and disadvantages, and the technical issues of these methods will be discussed and compared, and their applications in biomedical research will be presented.
Microcirculation is a complex network of small vessels that deliver blood, nourishment, and molecules to tissues and organs, playing a crucial role in their maintenance and hemodynamic. Therefore, its impairment and dysfunction are involved in a variety of pathological processes. Moreover, the measurement of the blood flow velocity provides essential information about subject health, pathological conditions, diagnosis of diseases, and the development and control of the response to treatment. This Spotlight reviews the basic operational principles, advantages/drawbacks, and the applications to the biomedical research of different noninvasive optical methods to measure the blood flow velocity, based both on whole-field and scanning imaging techniques.