Yutaka Fukuoka

Laser Doppler microscope for high accuracy velocity measurement of microcirculation

The velocity of red blood cells in the microcirculation of rat mesenteries was measured by using a laser Doppler microscope (LDM). The LDM system must be improved to provide accurate measurement, because there are some inherent disturbances on measuring the flow velocity in a microscopic area. The authors investigate the spurious Doppler signals, which are the most serious problem in LDM measurement, and develop an optical arrangement for eliminating the effect of spurious components. In vitro and in vivo microscopic flow measurements showed that the impaired system provides high-accuracy velocity measurement for a microscopic area.<<ETX>>

Spectrum analysis of fluctuations of RBC velocity in microvessels by using microscopic laser Doppler velocimetry

The velocity of red blood cells (RBCs) in microvessels of rat mesentery was measured using microscopic laser Doppler velocimetry. In order to estimate the periodicity of the RBC velocity fluctuation accurately, the power spectrum of the velocity was calculated by means of the fast Fourier transform. The amplitude of the pulsatile component was quite large in the spectrum of the RBC velocity fluctuation in arterioles. On the other hand, RBC velocity in venule intermingled the different frequency components. The velocity of the phase shift of the pulsatile component of RBC velocity was estimated by using the cross-spectrum analysis. The propagational velocity of the RBC velocity profiles in arterioles was slower than that of the pulse wave in larger vessels.<<ETX>>

Application Of Learning Signal Processing System On RBC Velocity Measurement Using Laser Doppler Technique

This paper describes first application of learning signal processing system on blood velocity measurement. The system has been developed to increase accuracy of the measurement at low S/N ratio. Artificial neural network constructed in the system learns pulsatile fluctuation of the velocity in order to predict the succeeding vzlocity signals adaptivelY. Velocity of red blood cells (RBCs) in microvessels of rat mesentery was measured by using microscopic laser Doppler velocimeter (MLDV). Cardiac pulsation apparently affects on the RBC velocity even in arterioles, however, detection of the pulsatile component in RBC velocity fluctuation using the conventional signal processor is very difficult because of its low S/N ratio. In contrast, the learning signal processing system which is pretrained can detect the component at the low S/N ratio. The results processed by the proposed system are compared with the results obtained by the conventional processor.

Application Of Microscopic Laser Doppler Velocimeter For Analysis Of Arterial Pulse Wave In Microcirculation

A microscopic laser Doppler velocimeter was applied for analysis of arterial pulse wave velocity in microcirculation in rat mesentery. The propagation velocity of arterial pulse wave was deduced from the phase delay of the velocity wave which can be obtained from the measurements of the RBC velocity at several positions along single microvessels. The RBC velocity fluctuation at each position was measured with the microscopic laser Doppler velocimeter. It was found that the propagation velocity in arterioles was much slower than that in arteries.

Signal processing system using a neural network for laser Doppler velocimetry

A signal processing system using a neural network for the laser Doppler velocimetry is described. The proposed system is based on spectrum analysis using a fast Fourier transform and adaptive prediction using a neural network. The neural network learns fluctuation of the velocity using the backpropagation algorithm and predicts the velocity related to the Doppler frequency adaptively. Actual measurement on a rotating acrylic disk was carried out. An increase in the accuracy of the velocity measurement was obtained.<<ETX>>

Spiral optical‐frequency shifter for lower‐velocity measurement of the laser Doppler velocimeter

A spiral optical‐frequency shifter for the laser Doppler velocimeter (LDV) is described, which offers lower shifted frequencies of 50 Hz–50 kHz manually. These lower shifted frequencies cannot be easily obtained from conventional optical‐frequency shifters (Bragg cell, rotating diffracting grating, etc.). However, these lower shifted frequencies are useful for LDV measurement of lower‐velocity flow such as blood flow in microvessels. A spiral optical element consisting of acrylic resin (refractive index, n=1.61) is inserted into one of the dual incident beams of a differential LDV, in which an optical frequency shift is brought about by rotation of the spiral element. The shifted frequency is changed by rotational frequency mechanically. The performance of the shifter is discussed; the experimental results are in good agreement with the theoretical values of shifted frequencies (error <1%).

Velocity and moving angle measurements of solid surfaces by simple velocimetry

A simple laser Doppler velocimeter constructed for measuring the velocity and moving angle of a moving surface simultaneously is described. This instrument accomplished two‐component velocity measurement for a solid surface by using the characteristic of specular reflection of the solid surface.