Ultrasound is the collective term for sound frequencies that are above those frequencies human beings are able to detect. Ultrasound is also the colloquial term for sonography, an examination using ultrasound frequencies.
During a sonography or so-called ultrasound examination, a contact gel is put on the area to be examined and a probe. This probe is placed onto the skin and sends ultrasound waves being reflected from the borders of different body tissues. Information on these tissues are detected by the ultrasound device and reconstructed. This way, an image for diagnostic purposes is created.
Ultrasound examinations/sonography is not harmful and is even used to examine the unborn live previous to birth.
Angiologists use different ultrasound techniques (e. g., B-mode, duplex and triplex sonography) to examine blood vessels.