(BTU/Hr) BTU/Hr is a common measure of heat transfer rate. Capacities of furnaces and boilers are for example expressed in thermal units per hour (British unit). One BTU/Hr is the amount of heat required to heat one pound of water one degree Fahrenheit per hour.
BTU/Hr is the unit that expresses how much the ultrasound machine heats up the surrounding area.

See also Thermal Effect, Ultrasound Physics.

Microwave thermotherapy is a type of ultrasound treatment in which body tissue is exposed to high temperatures. Focused ultrasound waves with high intensity damage and kill cancer cells or to make cancer cells more sensitive to the effects of radiation and certain anticancer drugs.
Examples for such treatments are the transurethral microwave thermotherapy (TUMT) and transurethral needle ablation (TUNA) that are used for benign prostatic hyperplasia.

See also High Intensity Focused Ultrasound and Ultrasound Therapy.

The third generation ultrasound contrast agents (UCA/USCA) are more echogenic and stable, and are able to enhance the echogenicity of parenchyma on B-mode images. These microbubbles may thus show perfusion, even in such a difficult region as the myocardium.

See also History of Ultrasound Contrast Agents.

A thyroid ultrasound evaluates the size and shape of the thyroid gland and parathyroid glands. A thyroid ultrasound can show nodules, cysts, tumors, and an enlargement, but a sonogram cannot determine the function of the thyroid. Ultrasound guides the placement of the needle during a thyroid fine needle aspiration biopsy.

See also Sonographic Features, Ultrasound Imaging Modes, Anechoic, Beam Width Artifact and Enhancement Artifact.

(ITA) The time average intensity is the average ultrasound intensity calculated over the time between pulses.
Time average intensity = Pulse average intensity x Duty factor
For ultrasound systems, the instantaneous intensity is averaged over one or more scan repetition periods for a specified scan mode.