(W) The SI unit of power.
Definition: 1 watt is equal to a power rate of one joule of work per second of time or in electrical terms it is the power produced by a current of one ampere flowing through an electric potential of one volt.
Power is the rate at which work is done, or the rate at which energy is expended and is used both in mechanics and in electricity.
The unit is named for James Watt, a British engineer.

From SIUI Inc.;
'The Apogee 800Plus ultrasound system offers a new level of high quality in image. With broad clinical application, the system delivers ease of use for cardiac and vascular exams.'
'Due to the exceptional image quality, the sensitivity of color Doppler and many other advanced features, the Apogee 800Plus offers complete diagnosis capability for your entire patient population, including abdominal, obstetrics, gynecology, adult cardiology, pediatric cardiology, peripheral vascular, small parts, breast, prostate, transcranial, etc.'

In physics, the absorbed dose is the ultrasonic power absorbed per unit of mass of an object, and is measured in watts per kilogram (W/kg). The absorption increases with ultrasound intensity and frequency.
The thermal index describes the potential for heating of the patient's tissue due to the application of energy.

See also Thermal Effect, Ultrasound Safety, Ultrasound Regulations.

The acoustic power of sound and ultrasound is the energy delivered per unit of time. The power is measured in Watt (W) and is proportional to the square of the amplitude.
1 W = 1 joule/second.

See also Directivity Index, Spatial Average Intensity, and Source Level.

(A or amp) The SI base unit of electric current.
Definition: Two parallel conductors, infinitely long and having negligible cross section should be placed 1 meter apart in a perfect vacuum. One ampere is the current that creates between them a force of 0.2 microNewton per meter of length.
One ampere represents a current flow of 1 coulomb of charge per second.
One ampere of current results from a potential distribution of 1 volt per ohm of resistance, or from a power production rate of 1 watt per volt of potential.
The unit is known informally as the amp, but A is its official symbol and is named for the French physicist André-Marie Ampère.

See also System International.