= Koroku Namekawa
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\b[Koroku Namekawa] is an Aloka coauthor of the 1985 <Color Doppler> imaging paper with <Chihiro Kasai>, <Akira Koyano> and <Ryozo Omoto>. Their instrument combined pulse-echo acquisition with complex correlation processing; the paper reports experiments with moving targets and flowing water.<Real-Time Two-Dimensional Blood Flow Imaging Using an Autocorrelation Technique by Chihiro Kasai and others>[Printed pp. 458–461: byline, system and experiments]{ref} The shared authorship establishes his participation; it does not assign each circuit or experiment to one coauthor.
A useful engineering constraint is the acquisition-time budget. If an image has $N$ beam directions, each uses $n$ pulses separated by $T$, and overhead is ignored, its acquisition time is approximately
$$
t_{\rm frame}=NnT,\qquad F\approx\frac{1}{NnT}.
$$
For an original example, $N=50$, $n=8$ and $T=0.20\,\mathrm{ms}$ give $t_{\rm frame}=0.080\,\mathrm s$ and $F=12.5$ frames per second. Doubling the ensemble to 16 pulses halves that ideal rate. These stipulated values illustrate the timing constraint, rather than a performance specification of Namekawa's instrument.
Longer averaging can improve a noisy <autocorrelation> estimate while reducing temporal coverage or image rate. It cannot create time that was not available between transmitted pulses. Thus a <blood flow> image is the outcome of both an estimator and a scanning schedule, not a simultaneous velocity observation at every displayed pixel.
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