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STRUCTURE AND DESIGN

Transesophageal echocardiography (TEE) presents a unique opportunity to overcome the limitations posed by chest wall acoustic windows while allowing visualization of cardiac structures with greater spatial resolution. Since its first reported use to evaluate intracardiac flow in 1971 and to visualize cardiac structures in 1976, the TEE probe has undergone remarkable technological advancement in terms of imaging capability and probe structure and design.1,2 The TEE probe used by Frazin et al1 consisted of an M-mode transducer attached to a coaxial cable. Souquet et al3 then reported successful use of a phased array transducer attached to the end of a gastroscope, which, in addition to producing two-dimensional images, allowed for finer control of the transducer position by using the flexion and angling controls akin to a gastroscope. The biplane transducer was then introduced in 1984, followed by the multiplane transducer in 1992.4 Consistent technological developments, including the introduction of a flexible endoscope, probe temperature regulation, miniaturization, transducer design, addition of color and spectral Doppler, and three-dimensional imaging, have led to the widespread adoption of TEE in clinical care. Currently TEE accounts for approximately 5% to 10% of echocardiographic procedures.5

The modern TEE probe consists of the following components (see Fig. 2-1).

Probe Tip

TEE probe tips are miniaturized (adult 3D probes: ~17 × 13.5 × 38 mm and infant/pediatric probes: ~7.5 × 5.5 × 18.5 mm) and feature smooth contours to allow safe and comfortable insertion into the oropharynx. The acoustic lens and matrix array are housed in the probe tip. Modern TEE probes typically have an extended operating frequency range of approximately 3 to 7 MHz with a 90-degree field of view and usually allow 180 degrees of electronic rotation. The probe tip can also be flexed, extended, and angled left or right using dials on the probe handle. Generally, probes are capable of flexion of up to 120 degrees, extension of 60 degrees, and 45 degrees of left/right angulation, with some variation between manufacturers. TEE probes with three-dimensional imaging capabilities allow for live, zoom, biplane, and multibeat acquisition with or without color Doppler. Three-dimensional imaging is possible by performing a significant portion of beam forming within the transducer in highly specialized integrated circuits, which enable the fitting of thousands of piezoelectric elements into the tip of the transducer (see Chapter 23).

Probe Shaft

The TEE probe shaft houses flexible, mini-coaxial cables carrying signals to and from the transducers. The probe shaft ...

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