What is Echocardiography?
Echocardiography uses sound waves to noninvasively image tissues of
differing densities within the body. Sound waves travel at different
speeds through materials with different acoustic densities, a property
that varies with tissue density and elasticity. The sound waves used
to obtain cardiac images in echocardiography are ultrasound waves that
range in frequency from 2-12 MHz. Resolution of the images improves
with frequency, but the wavelength is shortened in the process, which
decreases the distance from the ultrasound transducer that can be
imaged. As a result, adults are usually imaged using a 2-4 MHz
transducer, while pediatric patients are imaged using a 7-12 MHz
transducer. The relationship between resolution and tissue depth is
qualitatively shown in the figures below (Figure 1).
Images shown within this tutorial were obtained by Dr. Lixue Yin of
Chengdu Sichuan, China, on an isolated swine heart. Transthoracic,
transesophageal, and intracardiac echocardiography transducers were
all utilized while the heart was beating and under direct endoscopic
visualization. For each anatomical feature shown in the flash
version of this tutorial, the direct visualization of that feature
will be shown, followed by echocardiography images for comparative
purposes. The text version of this tutorial will provide some
highlighted examples from the flash version.
Figure 1: Higher resolution images can be obtained with higher
frequency ultrasound waves, but at the expense of tissue penetration.