Contour mapping of the cutaneous microvasculature by computerized laser Doppler velocimetry

A probe holder for laser Doppler velocimetry was designed to allow a narrow (1.24-mm) probe to be moved in increments of 1.04 mm, approximately the width of the probe window itself, so that four contiguous 1-mm2 spots in a 2.29 x 2.29 mm area could be sampled. An area as large as 2.48 x 2.48 cm can be measured with this device. The flux was fed into a computer by an analog/digital board, for visualization as a wave-form on the monitor, and for analysis by fast Fourier transforms and power spectrum analysis. Each spot sampled was given a unique x,y coordinate and the mean amplitude of the flux was designated as the z coordinate. With the aid of software, the values of these three coordinates were mathematically processed to produce contour graphs with shading that represented a map of the arteriolar circulation in the skin. This methodology allows for accurate movement and placement of the probe on the skin and the ability to relocate a spot within 1 mm of its original location after intervals of hours to days. Video images of the superficial plexus at the sites where the maps were made confirm the topographic appearance of these maps. Data generated by these maps raise the intriguing possibility that microcirculatory vessels may be engaged in a division of labor--some involved primarily with tissue perfusion, others with thermoregulation.