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:

• ultrasound for the study of deep organs: liver, spleen, pancreas, kidneys,
• adrenals ultrasound of the superficial organs: skin-subcutaneous, muscles, tendons, superficial organs
• endocavitary ultrasounds: endovaginal, endorectal, endovascular, endoscopic