Tissue harmonic imaging: why does it work?
Thomas JD; Rubin DN
J Am Soc Echocardiogr 1998 Aug;11(8):803-8
The recent utilization of harmonic frequencies in the imaging of both tissue and contrast
agents has dramatically improved echocardiographic image quality. In contrast
harmonics, the harmonic frequency energy is generated on reflection from the
microbubble contrast agent. In tissue harmonics, the harmonic frequency energy is
generated gradually as the ultrasonic wave propagates through the tissue. Critical to the
utility of tissue-generated harmonic frequencies is their origin beyond the chest wall and
their nonlinear relation to the fundamental frequency energy strength. These two
characteristics of tissue-generated harmonics ensure that the echoes most likely to
produce artifact are least likely to produce harmonic waves. Armed with an understanding
of how these images are produced and with data emerging as to their clinical utility, we
anticipate that harmonic imaging will become the standard for assessing regional and
global left ventricular function in technically difficult studies.
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