Multiparametric Imaging of Microregional Circulation over the Brain Cortex by Videoreflectometry

Abstract

One of the primary tasks of parenchymal circulation is to distribute blood flow as it flows through an organ among increasingly larger number and smaller volumes of tissue elements until the level of nutritive microcirculation is reached. It seems, the only adequate approach to characterize this process is to map the distribution of blood flow at the level of microcirculation over tissue microareas. It has to be recognized, however, that the term blood flow is rather inadequate to describe the passage of its two components, erythrocyte and plasma flow through the complex system of capillary networks of tissue microareas where the diameter of capillaries and the traversing erythrocytes are comparable. The methodology of multiparametric imaging of tissue microcirculation by computerized videoreflectometry provides the means of obtaining high resolution maps of local erythrocyte and plasma volumes, mean transit times, volume flows, local tube and discharge hematocrit, blood volume and flow in a repeatable manner. Current state of instrumentation and technology (Eke 1992) has made multiparametric assessment of cerebrocortical circulation for these parameters possible typically at a spatial resolution of 10000 sites/10 mm² and a frequency of up to 1 measurement/minute. These features seem adequate to assess the complexity of tissue microcirculation in the brain cortex in the spatial and temporal domain alike.