(µ) Micro is often used as a synonym for very small; micro is mathematically one millionth of a unit. For example a microgram (µg) is one millionth of a gram.

See also Kilogram.

(N) The SI unit of force.
Definition: 1 newton will accelerate a mass of 1 kilogram at the rate of 1 meter 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.

Osmolality is the number of moles of osmotically active particles (molecules) present in solution per kilogram of water.
High osmolality of contrast agents is related to some of the adverse reactions.

Osmolality of iodinated contrast media:

(rad) One rad is the absorbed radiation dose of 100 ergs of energy by one gram or 0.01 joules of energy by one kilogram of matter. In the SI system of units, the rad is replaced by the gray (Gy). 1 Gy = 100 rad. See also Absorbed Dose Rate.

(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.