Hiromichi Mishina

Blood flow velocity in pulmonary microvessels of bullfrog

Flow velocity in the pulmonary microvessels of the exposed lung of bullfrogs was measured by means of a laser Doppler microscope of an oblique backward mode, together with a signal-analyzing system having a time sharing circuit triggered by the R-wave of the ECG. By these means, measurements of the changes of flow velocity contour in the cardiac cycle were made. Flow velocity was clearly pulsatile in response to cardiac cycles in all microvessels including capillaries. Flow velocities in the arteriole and venule consistently decreased for a short period after the R-wave (84 +/- 33 msec (mean +/- SD) in the arteriole and 130 +/- 31 msec in the venule, respectively) and rapidly increased up to a maximicronm value. The mean flow velocities in arterioles (diameter 50 +/- 17 micron) and venules (39 +/- 9 micronm) were 2.29 +/- 0.32 and 2.30 +/- 0.27 mm/sec. The amplitudes of pulsatile flow in these vessels were 0.83 +/- 0.31 and 0.63 +/- 0.16 mm/sec, respectively. In the capillary the times from the R-wave to the minimicronm and maximum values were variable. In some cases the velocity gradually increased without first decreasing and the increase sharply accelerated a certain time after the R-wave. The mean velocity in the pulmonary capillary and the amplitude of the pulsatile flow ere 1.78 +/- 0.31 and 0.37 +/- 0.12 mm/sec, resepctively. The ratios of the pulsatile amplitude to the mean velocity in the pulmonary capillary, venule and arteriole averaged 0.21, and 0.36, respectively.

Measurement of velocity fluctuations in laser Doppler microscope by the new system employing the time-to-pulse height converter

A new analyzing system for the laser Doppler microscope is proposed and constructed employing both the time-to-pulse height converter and the pulse height analyzer. Since it holds a sufficiently high sampling rate compared with other analyzing systems, it is very useful for measuring velocity fluctuations of the flow. By examining its properties, it is found that the envelope function of beat signals affects the dispersion of the final result for the flow velocity and that the noticeable choice of a trigger level can reject the most of noise. Some experimental results obtained by the present system are shown.

A study of micro-circulation in web of frog (Xenopus laevis Daudin) by using Laser Doppler microscope

The flow velocity profile in the venule of frog web was measured by using a laser Doppler microscope of a crossed-beam which permitted a measurement of flow velocity in a clearly defined small volume. The flow velocity profile in the venule seems to deviate slightly from the Newtonian parabola.

Laser Doppler microscope in an oblique-backward mode and pulsatile blood flow velocity in pulmonary arteriole

Blood flow velocity, pulsatile in correspondence to cardiac events, in pulmonary arterioles of anesthetized bullfrogs could be measured on lung surfaces covered with a water-containing plastic disc by means of a laser Doppler microscope arranged in an oblique-backward mode.

Two gaussian beam interference

The equation for the intensity distribution of interference patterns, in a two dimension, produced by the two Gaussian beams having different beam parameters and some deviations from each other is derived. Some interference patterns are shown as functions of the two ratios of beam intensities and widths and of the beam deviation. The interference patterns are discussed in connection with the property of output beat signals in a differential laser Doppler velocimeter. Some experimental results are finally shown.

Some effects of optical alignment errors in a differential laser Doppler velocimeter

A formulation has been developed to treat the effects of alignment errors of the optical system used in a differential laser Doppler velocimeter. It is then applied to analyse the properties of output beat signals obtained by the velocimeter. The effects of optical alignment errors on the spectral width and signal-to-noise ratio of the output beat signals and on the probing volume are investigated in some detail. The spectral width is not affected very much by the deviation of the angle between two beams incident on the probing volume, but depends mainly on the number of interference fringes produced in that volume. The signal-to-noise ratio is very sensitive to the displacement of two incident beams on the probing volume and is also affected by the intensity and beam width differences of these two beams. The probing volume is evaluated in the case of two incident beams having different beam widths.

Its optical and signal-analysing systems and some experimental results of flow velocity☆

Abstract A laser Doppler microscope, consisting of optical and signal-analysing systems, has been developed. Flow velocity can be measured with an extremely high spatial resolution over an area of up to 10μm in diameter. The optical system consists of a microscope having two types of penetrative and reflective systems. On the basis of the characteristic analysis of Doppler beat signals from the laser Doppler microscope, the signal-analysing system, which uses a tracking filter together with a digital-hold element and a time-to-pulse height converter, has been found to be the most suitable for analysing beat signals. Some experimental results obtained using the laser Dopller microscope for measuring flow velocities, both in a small square cell in a venule, and in a capillary over the web of a frogs foot are presented.

Some formulations of light scattering in laser flowmeters employing differential Doppler heterodyning

The theory for the Doppler shifted light is developed by diffraction theory combined with galilean transformation. The theory developed is applied to a differential Doppler heterodyning technique in which two beams are brought simultaneously, but at different angles, into the same area, and the cross region made by the two beams becomes a probing volume. When the concentration of scattering particles is so low that only one particle is found in the probing volume, the theory can be classified into two cases of a single particle and many particles depending on the analysing time for the Fourier transform, i.e. whether the time, during which one particle passes through the probing volume, is longer than the observing time or not. When the concentration of particles in the probing volume becomes dense, the light scattered by the different particles interferes and the theory shows great complexity. The cases of two particles and many particles showing a very high density are studied. Comparisons are made for the difference between differential Doppler heterodyning and normal heterodyning techniques.

Occurrence of eddy flow in the flowing plasma space in capillary blood vessel of frog web

Studies of capillary blood flow velocity by means of a laser Doppler microscope suggest the occurrence of eddy flow in the plasma space in the capillary blood vessel of frog web.

Zero-crossing probability density of Doppler beat signals in the wave-period measuring system

As an effect of shot noise on the analysis of Doppler beat signals in the wave-period measuring system, the zero-crossing probability density of beat signals is studied emphasizing two parameters, namely the bandwidth of a pre-filter and the signal-to-noise ratio.