= Akira Koyano
{c}
\b[Akira Koyano] is an Aloka coauthor of the 1985 real-time <blood flow> imaging paper with <Chihiro Kasai>, <Koroku Namekawa> and <Ryozo Omoto>. A particularly clear test in that paper moved a thread around motor-driven pulleys in a water tank and compared its speed with the velocity-calculator output.<Real-Time Two-Dimensional Blood Flow Imaging Using an Autocorrelation Technique by Chihiro Kasai and others>[Printed pp. 458 and 460–461: affiliation, moving-thread apparatus and Figure 3]{ref}
The thread makes the moving target controllable independently of a patient's circulation. For a simplified <Doppler ultrasound> calculation,
$$
f_D\simeq\frac{2f_0v\cos\theta}{c},
$$
where $f_0$ is transmitted frequency, $v$ target speed, $\theta$ the angle to the beam and $c$ sound speed. With stipulated $f_0=3\,\mathrm{MHz}$, $v=0.20\,\mathrm{m\,s^{-1}}$, $\theta=60\,{}^\circ$ and $c=1500\,\mathrm{m\,s^{-1}}$, the predicted shift is $400\,\mathrm{Hz}$. These are illustrative inputs, not a reproduction of a particular plotted data point.
A speed sweep at fixed geometry tests one part of the signal chain. An angle error changes the projection even if the frequency estimate is exact; changing target material can change echo strength. Bench agreement therefore supports the tested motion-to-output relation while leaving separate questions about scattering, anatomy and clinical interpretation.
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