CLINICAL FORMATS OF ULTRASOUND Current generation ultrasound systems allow display of all of the imaging formats discussed except 3D/4D imaging that is still limited in availability to some high end systems. Specialized transducers that emit and receive the ultrasound have been designed for various clinical indications. Four common types of transducers are used (Fig. 1):
Transthoracic: By far the most common, this transducer is placed on the surface of the chest and moved to different locations to image different parts of the heart or great vessels. All display formats are possible (Fig. 2).
Transesophageal: The transducer is designed to be inserted through the patient’s mouth into the esophagus and stomach. The ultrasound signal is directed at the heart from that location for specialized exams. All display formats are possible. Intracardiac: A small transducer is mounted on a catheter, inserted into a large vein and moved into the heart. Imaging from within the heart is performed to monitor specialized interventional therapy. Most display formats are available. Intravascular: Miniature sized transducers are mounted on small catheters and moved through arteries to examine arterial pathology and the results of selected interventions. Limited 2D display formats are available some being radial rather than sector based. The transducers run at very high frequencies (20–30 MHz). Ultrasound systems vary considerably in size and sophistication (Fig. 3). Full size systems, typically found in hospitals display all imaging formats, accept all types of