Shimpei Kohri

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

A miniaturized fiber-optic laser Doppler velocimetry sensor has been developed to measure the local blood velocity in vivo. The laser beam emitted from the sensor tip can be focused at any distance between 0.1 and 0.5 mm from the tip. Consequently, the sensor has a sufficiently high signal-to-noise ratio to measure the local velocity in almost any opaque fluid, including blood. The sensor head is inserted in an injection needle or a catheter tube. In the former case, it is inserted at an angle to the wall of a vessel and is scanned across the vessel to measure the velocity distribution. 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 be measured very accurately. The insertion angle of the fiber into the flow significantly affects the measurement accuracy; an angle of about 50° is suitable when an injection needle is used. When a catheter is employed, an insertion direction opposite to the flow direction is better than parallel to the flow due to the generation of a wake behind the fiber.

Development of a Miniaturized Fiber-optic LDV Sensor for Local Blood Velocity Measurement

131 DOI: 10.5963/BER0203002 Development of a Miniaturized Fiber-optic LDV Sensor for Local Blood Velocity Measurement Local Velocity and Flow Profile Measurement of Pulsatile Blood Flow Modeled in Humans Shimpei Kohri, Tsutomu Tajikawa, Kenkichi Ohba Department of Medical Engineering, Aino University 4-5-4, Higashiohda, Ibaraki city, Osaka 567-0012 Japan Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-8680 Japan s-kohri@me-u.aino.ac.jp

Development of New Method for Discriminating Embolus from Air Bubble in Pulsatile Blood Flow Using Ultrasound

Patients who have operation for artificial valve substitution frequently suffer from brain embolism. Micro air bubbles are generated with opening and closing of an artificial valve in such a patients blood. It is difficult to discriminate air bubbles from emboli by methods using ultrasonic wave. Hence, we tried to develop a new method for discriminating embolus from air bubble in pulsatile blood flow using ultrasound. We utilized the difference in motion of embolus and an air bubble when they are irradiated by ultrasound beam. It is considered that the difference in motion is caused from the difference in acoustic impedance and mass of them. As a result, we succeeded to discriminate emboli from micro air bubbles in pulsatile flows as well as in steady flow in the model experiments in vitro.