Ultrasound or echotomography is a medical diagnostic investigation system that does not use ionizing radiation, but ultrasound and is based on the principle of echo emission and transmission of ultrasound waves. This technique is routinely used in the internal, surgical and radiological fields. Today this method is considered as a basic or filter examination with respect to more complex imaging techniques such as CT, magnetic resonance imaging, angiography.
Ultrasound is, in any case, operator-dependent, since special manual skills and spirit of observation are required, in addition to image expertise and clinical experience. The ultrasound used is between 2 and 20 MHz. The frequency is chosen taking into account that higher frequencies give greater resolution of the image, but penetrate less deeply into the patient.
Although numerous types of ultrasounds are possible , they can be grouped into three types: