(R) R is a unit to express exposure to radiation (x-rays or gamma rays). 1 R corresponds to the generation of approximately 2.08 x10⁹ ion pairs (1 electrostatic unit of charge) (in 1 cm³ of dry air at 0 °C and 760 torr). 1 R, converted to SI, equals 2.58 x10^-4 coulombs per kg of air.

(rem) The rem is the dose equivalent of the absorbed dose considering the biological efficiency of the radiation, also called quality factor. With a quality factor of 1 is 1 rem equal to 1.07185 roentgens. One millirem is one thousandth of one rem.
In the SI system of units the rem is replaced by the sievert (Sv), which is numerically equal to the absorbed dose in gray modified by a radiation weighting factor. The conversion factor has been readjusted from 1 to 1.07185 so that 100 rem are equal to 1 Sv.

(Sv) The sievert is the SI unit of a dose equivalent, which accounts for relative sensitivities of different tissues and organs exposed to radiation. The effective dose, usually measured in millisievert (mSv), attempts to reflect the biological effects of radiation. One sievert equals an ionizing x-ray or gamma radiation energy loss of 1 joule per kilogram of body tissue (1 gray). One sievert is equivalent to 100 rem.
It is named after Rolf Sievert, a Swedish medical physicist.

Viscosity is measured in centipoise (cP). The viscosity of water at 20° C is approximately 1 cP. Viscosity depends on temperature, size and shape of the dissolved particle.
The viscosity of contrast agents is an important factor in diagnostic imaging procedures like angiography and other studies where the injection rate can be of critical importance. Warming the contrast agent to body temperature may achieve higher flow rates. Contrast media are approximately twice as viscous at 20° C as at body temperature.

(V) The SI unit of electric potential.
Definition: The amount of potential energy present per unit of charge. 1 volt represents a potential of 1 joule per coulomb of charge.
The unit is named for the Italian scientist Count Alessandro Volta.

(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.