Ultrasound imaging procedures are widely used in medicine. It is possible to perform diagnostic or therapeutic procedures with the guidance of ultrasonography (interventional ultrasound biopsies or drainage of fluid collections). Sonography or ultrasound scanning involves the application of an ultrasound transducer used to transmit high frequency sound waves, which bounce off internal structures to produce an image that can be displayed and recorded.
Ultrasound imaging procedures include for example:

Regulations governing the output of diagnostic ultrasound have been largely set by the USA's Food and Drug Administration (FDA), although the International Electrotechnical Commission (IEC) is currently in the process of setting internationally agreed standards.
The relevant national societies for ultrasound users (e.g. American Institute of Ultrasound in Medicine (AIUM), British Medical Ultrasound Society (BMUS)) usually have safety committees who offer advice on the safe use of ultrasound. In 1992, the AIUM, in conjunction with the National Electrical Manufacturers Association (NEMA) developed the Output Display Standard (ODS), including the thermal index and mechanical index which have been incorporated in the FDA's new regulations.
Within Europe, the Federation of Societies of Ultrasound in Medicine and Biology (EFSUMB) also addresses safety and has produced safety guidelines (through the European Committee for Ultrasound Radiation Safety). The World Federation (WFUMB) held safety symposia in 1991 (on thermal issues) and 1996 (thermal and non-thermal issues), at which recommendations were proffered.
The FDA ultrasound safety regulations from 1993 combine an overall limit of spatial peak time averaged intensity (I-SPTA) of 720 mW/cm2 for all equipment. A system of output displays allows users to employ effective and judicious levels of ultrasound appropriate to the examination. The output display is based on two indices, the mechanical index (MI) and the thermal index (TI).

See also ALARA Principle, and Radiological Society of North America.

Urologic ultrasound includes the examination of the kidneys, renal vessels, urinary tract, bladder, prostate, and scrotum.
Usual gray scale ultrasound equipment and standard probes are sufficient to examine the kidney parenchyma and renal pelvis, the urinary tract and bladder. Doppler ultrasound is a useful adjunct to kidney ultrasound. High ultrasound system performance is desirable to show the arterial system, because advanced power Doppler is significantly more sensitive to blood flow than standard color Doppler.
Transurethral sonography may be used to examine the bladder and urethra. Transrectal sonography is used to scan and treat the prostate e.g., with brachytherapy or high intensity focused ultrasound. Very small probes are used for these applications. Reflux sonography is especially used in pediatric ultrasound.

See also Ultrasound Imaging Procedures, Ultrasound Picture, Ultrasound Imaging Modes, Lithotripsy, Thermotherapy, Brachytherapy and Ultrasound Therapy.

Windows are areas where the skull bones are relatively thin or where the naturally occurring forage allows proper penetration of the ultrasound beam. These windows are commonly used for transcranial Doppler (TCD) examinations. However, in the best of cases, only approximately 6% of the intensity of the US used reaches the brain substance.

Different usual windows: