Catheter Velocimeters

Abstract

The laser-Doppler velocimeter is potentially a very powerful device for measuring intravascular blood flow velocity. Because light can be delivered and collected through optical fibers of very small diameter, the technique lends itself naturally to use through a catheter passed through the blood vessel. The small size of optical fibers also permits high spatial resolution, so that flow velocity at a single point in the cross section of a blood vessel can be measured. However, because catheters disturb the flow of blood in their neighborhood, and because light is multiply scattered in passing through blood, combining the high spatial and temporal resolution of (LDV) laserDoppler velocimetry with catheter delivery is not straightforward. At the present time, the development of instruments for the practical measurement of blood flow velocity through a catheter is an area of active research. In this chapter, we will present the principles behind this work, and will indicate the present state of the art and the potential uses of catheter LDV systems.