Page 15 - Ultrasonography in Prehospital and Emergency Medicine - Rein Ketelaars

Introduction
What is ultrasonography?
Ultrasonography is a diagnostic imaging technique based on high-frequency sound waves. In medicine, it is used to visualize organs and other structures inside the body. For instance, the heart, spleen, liver, kidneys, and major vessels as well as the chest wall and the surface of the lungs can be visualized. The aim is to detect or exclude pathology such as pericardial effu- sion, abnormal cardiac motility, free intraperitoneal fluid, a hemothorax or a pneumothorax. Besides these, there is a myriad of other indications for ultrasonography. Also, some thera- peutic uses for ultrasound have been developed, as discussed in more detail in Chapter 2 of this thesis.
The human ear can perceive sounds with frequencies between 20 Hz and 20 kHz. The fre- quency of the sound waves used in ultrasonography lie well above the audible range and are therefore called ultrasound. In medical applications, the ultrasound frequencies are usual- ly chosen in a range between 1 and 20 MHz. However, transducers with frequencies up to 71 MHz are on the market and ultrahigh frequency transducers of up to 300 MHz are in development.1
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oroigrignianlawlawveave Figure 1.1 The reflection of ultrasound waves in the animal kingdom
Introduction, aims, and outline of this thesis 13
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