Abstract
Ultrasonography is free of ionizing radiation but during the examination it is accompanied by energy deposition in the tissue. Therefore, users should be familiar with the mechanisms of action and possible risks. Thermal and non-thermal (e.g. cavitation) effects are related to the intensity and sound pressure of ultrasound waves and are therefore also dependent on the ultrasound modality used, e.g., B‑mode, color Doppler and/or pulsed wave (pw) Doppler. With B‑mode ultrasound no dangerous thermal effects are to be expected. In embryos and foetuses as well as febrile patients caution should be exercised. The pw Doppler mode can cause temperature spikes and the risks increase with the duration of use. Ultrasound contrast media are pathogenic for cavitation and should be avoided during the 24 h prior to shock wave lithotripsy. In ultrasound modalities with high local energy deposition, the values for the thermal index (TI) and mechanical index (MI) displayed on the screen should be observed and as with ionizing radiation, the ALARA (as low as reasonably achievable) principle should be adhered to.
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