2007 Volume 45 Issue 4 Pages 298-306
For measurement of local blood velocity, a less invasive miniaturized fiber-optic LDV (laser Doppler velocimetry) sensor which was directly inserted into a blood vessel was developed as a monitoring device for clinical use and in vitro testing equipment. By using the process of a chemical etching with a HF-NH4F buffer solution, a convex lens-like surface was formed on the fiber tip having a core of 50 μm. Laser beam emitted from the fiber tip was focused and formed measuring volume. In the authors' previous studies, the local velocity of a steady blood flow was successfully measured using a same type of the present fiber-optic LDV sensor. In order to measure local velocity in a pulsatile flow, the optical system and the curvature of the fiber sensor tip were improved. The fiber sensor was inserted at an insertion angle of 120 deg. through an injection needle into a flow duct of an acrylic pipe in which an opaque fluid as a model of whole blood was pulsatingly flowing. The waveform of the flow rate was modeled after the human middle cerebral arterial flow. In this experiment, the local flow velocity and velocity profile across the duct were measured in a pulsatile flow of a dense suspension of a white pigment. The results measured by this sensor were compared both with that by a fringe-mode LDV and with that calculated on the basis of Womersley's oscillatory flow theory. As a result, it was found that the local velocity and its profile across the duct in the pulsatile flow were successfully measured by the present fiber-optic LDV sensor, which proved the capability of the sensor as a diagnostic device.
