Transducers can be divided in:
1.) Transducers where the sound wave is transmitted and received by different elements.
2.) Transducers where multiple elements part of the time transmit and part of the time receive sound energy.
The first type of ultrasound transducer is used in detection of blood flow (also called nonimaging transducers). For example, the continuous wave transducer (Pedoff transducer) has two separate elements, where one element is always transmitting while the other element is always receiving.
Probes of the second type are used to image cardiac structures and have the capability to use various Doppler techniques to detect blood flow (also called imaging transducers). For example, continuous wave, pulsed wave, high pulse repetition frequency, color flow, M-mode, and 2D-mode are the various modes that this type of transducer can perform.

Transducers can also be divided in mechanical and electronic or phased scan types.
Mechanical transducers use a combination of single element oscillation, multiple element rotation, or a single element and set of acoustic mirrors to generate the sweeping beam for 2D mode. Caused by the vibration (created as the mirrors rotate or oscillate inside the cover) is this type sometimes called the 'wobbler'. Mechanical transducers are cheaper than electronic transducers.
Different types of electronic or phased array probes can create a linear or rectangular shaped scan plane as well as a sector or pie shaped scan plane. Sector scanners are most useful for cardiac ultrasound examinations where the beam is directed between the ribs to image the heart. A linear array transducer is more useful in abdominal, OB/GYN, and small parts examinations. Electronic transducers are more expensive but they provide dynamic focusing and smaller probe.

See also Rectangular Array Transducer.

(TTE) Transthoracic echocardiography is a common type of cardiac ultrasound and is used to evaluate the size and function of the heart.

Indications:
TTE requires no sedation or special patient preparation. After the application of ECG electrodes and ultrasound couplant, the probe is maneuvered over the chest in the area adjacent to the breast bone and under the left breast, to provide the different views of the heart. Usually the images will be obtained lying relaxed on the left side. Other views can be sampled lying on the back with the knees bent, or sitting in an upright position.

See also Bicycle Stress Echocardiography and Transesophageal Echocardiography.

Vascular ultrasound obtains images and measures blood flow velocity in the carotids, abdominal aorta, and vessels of kidneys, arms, or legs. Blockages in arteries, blood clots in veins, or abdominal aortic aneurysm can be detected.
These abnormalities in blood flow are usually examined with different Doppler techniques. In addition, the speed and direction of blood flow can be color coded in a color map. Duplex techniques show both, the vessels and the surrounding tissue. The use of ultrasound contrast agents improves the left ventricular opacification in cardiac ultrasound examination. Usually, for a vascular ultrasound no special preparation is needed.

See also Echocardiography, Venous Ultrasound, Adventitia, Intima, Temporal Mean Velocity, and Intravascular Ultrasound.

From Philips Medical Systems;
Introduced in June 2005, 'one of the less expensive and more dedicated' ultrasound systems.

From GE Healthcare.;
'GE is defining a new age of ultrasound. We call it Volume Ultrasound. GE's Voluson 730 Expert is a powerful system that enables real-time techniques for acquiring, navigating and analyzing volumetric images so that you can make clinical decisions with unprecedented confidence.'