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.