(kg) The base SI unit of mass of the metric system.
Definition: 1 kilogram is defined as the mass of the standard kilogram, a platinum-iridium bar in the custody of the International Bureau of Weights and Measures (BIPM) near Paris, France.
A traditional unit of mass or weight is also the pound (in general use, e.g. in the United States and Great Britain), with the symbol lb (derived from the Latin word libra).

1 kg = 2.204627 pound (lb. av., lbs.)
1 pound (lb. av., lbs.) = 0.453 kg.

Smaller units are, e.g.
1 000 gram (g) = 1 kg
1 000 milligram (mg) = 1 g
1 000 microgram (μg) = 1 mg

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.

(J) The SI unit of work or energy.
Definition: The work done by a force of 1 Newton acting to move an object through a distance of 1 meter in the direction in which the force is applied.
Since kinetic energy is one half the mass times the square of the velocity, 1 joule is the kinetic energy of a mass of two kilograms moving at a velocity of 1 m/sec.
The joule is named for the British physicist James P. Joule.

(N) The SI unit of force.
Definition: 1 Newton will accelerate a mass of 1 kilogram at the rate of 1 meter per second per second.
The relationship between force (F), mass (m), and acceleration (a) is expressed by the formula F = ma.
The Newton is named for Isaac Newton (1642-1727), the British mathematician, physicist, and natural philosopher.

The Osmolality is the osmotic concentration, an indicator of fluid balance in the body's tissues.
Osmolal describes an ion concentration of a solution in moles per kilogram of solvent (mol/kg), while osmolar describes an ion concentration in moles per liter (mol/L).