Ultrasound

Ultrasound is a medical diagnostic survey system that doesn’t use ionizing radiation, but ultrasounds and is based on the principle of echoes issue and ultrasonic waves transmission. This method is considered as a basic examination or filter compared to more complex imaging techniques as CT scans, magnetic resonance imaging, angiography.
In the interventional radiologist’s hands this method can be used for minimally invasive therapeutic procedures.

Ultrasound is an operator-dependent procedure, since it is required a particular manual skill and a spirit of observation, in addition to the culture of the image and a clinical experience.

These waves are generated by a piezoceramic crystal inserted in a probe maintained in direct contact with the patient's skin with the interposition of a special gel that eliminates the air between the probe and the patient's skin, allowing ultrasounds to penetrate into the anatomical segment examined; the same probe is able to gather the return signal, which is appropriately elaborated by a computer and presented on a monitor.

Source: extract from Wikipedia