Development of Miniaturized Fiber-Optic Laser Doppler Velocimetry Sensor for Measuring Local Blood Velocity: Measurement of Whole Blood Velocity in Model Blood Vessel Using a Fiber-Optic Sensor with a Convex Lens-Like Tip

摘要

A miniaturized fiber-optic laser Doppler velocimetry sensor has been developed to measure the local blood velocityin vivo. The laser beam emitted from the sensor tip can be focused at any distance between 0.1 and 0.5 mm fromthe tip. Consequently, the sensor has a sufficiently high signal-to-noise ratio to measure the local velocity in almostany opaque fluid, including blood. The sensor head is inserted in an injection needle or a catheter tube. In theformer case, it is inserted at an angle to the wall of a vessel and is scanned across the vessel to measure the velocitydistribution. In the latter case, it is aligned parallel with the flow in a vessel. For all flows of whole human blood,whole caprine blood, and 69% hematocrit of bovine blood, the velocity distribution across the vessel could bemeasured very accurately. The insertion angle of the fiber into the flow significantly affects the measurementaccuracy; an angle of about 50° is suitable when an injection needle is used. When a catheter is employed, aninsertion direction opposite to the flow direction is better than parallel to the flow due to the generation of a wakebehind the fiber.