Page 19 - Ultrasonography in Prehospital and Emergency Medicine - Rein Ketelaars
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                 Inversely, ultrasound waves penetrate deeper with lower frequencies and thus a lower num- ber of oscillations/wavelengths for a traveled distance. For instance, common low-frequency transducers (frequency range of 5–1 MHz) can visualize structures at a depth of up to 35 cm.
However, the trade-off here is that the resolution of the ultrasound image is determined by the wavelength of the ultrasound wave in the tissue. A longer wavelength, emitted by low-frequency transducers, will yield a lower image resolution compared to high-frequency (short wavelength) transducers. This trade-off between tissue penetration and wavelength (and thus image resolution) is displayed in Figure 1.7.
Introduction, aims, and outline of this thesis 17
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ultrasound frequency (MHz)
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  Figure 1.7 Ultrasound penetration vs wavelength and resolution Pros and cons of ultrasonography
Ultrasonography is almost entirely harmless because sound waves are used instead of harm- ful electromagnetic waves such as X-rays. No long-term side effects are known and it rarely causes any discomfort to the patient. Therefore, image acquisition can be repeated without penalty. Ultrasonography produces live images, allowing to support decision-making in re- al-time. It is reproducible, repeatable, and relatively low-cost. Highly portable equipment is available and can therefore be brought to the bedside such as in the emergency department (ED), the intensive care unit (ICU), and in the prehospital setting. It is easy to learn, al- though adding experience improves successful image acquisition and the diagnostic perfor- mance of the technique.2
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 wavelength (mm)
penetration (cm)











































































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