J Med Ultrasonics (2013) 40:89
DOI 10.1007/s10396-013-0433-8

EDITORIAL

Rapid change in environment for research on diagnostic
ultrasound
Hideyuki Hasegawa

Published online: 19 February 2013
Ó The Japan Society of Ultrasonics in Medicine 2013

For progression of research, of course, experimental systems play an important role. Fifteen years ago, at the startof my research career, it was still difficult for researchers,maybe particularly for researchers in universities, to obtainan experimental system that was capable of acquiring
beamformed ultrasonic radio-frequency (RF) echoes froman ultrasonic array transducer, due to the limitations of theavailable hardware, e.g., low sampling frequency and thelimited memory of the analog-to-digital (A/D) converter. In
our case, we were forced to use base-band signals (composed of in-phase and quadrature signals) to acquire
ultrasonic signals for longer acquisition periods with alimited amount of memory because acquisition of beamformed RF signals required a higher sampling frequency
and more memory. Even for acquisition of base-band signals, we needed to develop an expensive in-house acquisition system to acquire the base-band signals of
beamformed ultrasonic RF echoes for several seconds. The
sampling frequency and amount of memory for thein-house system were 10 MHz and 16 MB, respectively.
There was a severe tradeoff between sampling frequency
and the period available for acquisition (amount of memory). For example, for research on ultrasound imaging, it isdesirable to acquire RF signals, which requires a highsampling frequency, and, thus, the number of framesacquired is reduced. On the other hand, in the case of
research involving measurement of tissue motion, forexample, it is necessary to acquire ultrasonic signals for aH. Hasegawa (&)
Graduate School of Biomedical Engineering,Tohoku University, Sendai, Miyagi, Japane-mail: hasegawa@ecei.tohoku.ac.jp

certain required period and the sampling frequency should
be limited. Therefore, signals such as base-band signals
were preferred because they did not require a high sampling frequency.
In the past decade, the capability of acquisition systems
has improved dramatically. Now we are able to obtain anacquisition system with a much higher sampling frequency
and more memory. At around the year 2000, such systems
implemented acquisition of beamformed RF signals for acertain required number of frames, e.g., for several seconds. However, it was still difficult to acquire ultrasonicRF echoes received by each element of an ultrasonic arraytransducer (channel RF signal). Therefore, there were very
few research groups who could develop and implement
methods for diagnostic ultrasound imaging using RF signals obtained from array elements, though there shouldhave been many good ideas on diagnostic ultrasoundimaging based on array signal processing.
However, systems capable of acquiring channel RF
signals and also controlling the transmitted ultrasonic field
have become available at last due to further innovation in
the capability of acquisition systems. Such systems are still
not cheap, but now we are able to obtain such systems
much more easily than before.
As described above, there was a severe tradeoff in thepast, i.e., higher sampling frequency and shorter acquisition period to acquire RF echoes or lower sampling frequency and longer acquisition period based on base-band
signals. However, now we have been freed from such
limitations. Current ultrasound acquisition systems, which
are able to acquire channel RF signals and control thetransmitted ultrasonic field, will significantly broaden theopportunities for research on diagnostic ultrasound imaging, and the prevalence of such systems may lead to
explosive progression in related research fields.

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