Mapping of cerebral cortical strokes in Rhesus monkeys by laser Doppler spectroscopy

We have demonstrated the feasibility of using laser doppler spectroscopy to map regional blood flow distribution on the surface of the cerebral cortex. Rhesus monkeys underwent craniotomy, with replacement of part of the calvarium by a transparent plastic dome. A stroke was produced on one side by ligation of the middle cerebral artery. A flow index was computed from a weighted bandwidth of the doppler spectrum of helium-neon laser light scattered from the surface of the cortex, the doppler shift being due to scattering from moving blood cells in the microcirculation. By measuring the doppler flow index at a grid of points over the surface, the region of the stroke was easily delineated, and its progression with time observed. The method provides a rapid measurement with a spatial resolution of about 1 mm.