(dB/dt) Definition: The ratio between the amount of change in amplitude of the magnetic field (dB) and the time it takes to make that change (dt). Because changing magnetic fields can induce electrical fields, this is one area of potential concern for MRI safety limits.
The value of dB/dt is measured in Tesla per second (T/s).
See also Phon and Decibel.

(dB) A customary logarithmic measure most commonly used (in various ways) for measuring sound. If one sound is 1 bel (10 decibel) 'louder' than another, this means the louder sound is 10 times louder than the fainter one. A difference of 20 decibel corresponds to an increase of 10 x 10 or 100 times in intensity.
For sound pressure (the pressure exerted by the sound waves) 0 decibel equals 20 micropascal (μPa), and for sound power 0 decibel sometimes equals 1 picowatt.

See also Phon and Acoustic Noise.

This unit of temperature is still used customarily in the United States.
Definition: 0°F is the coldest temperature achieved by using an ice and salt mixture, and 100°F is set at the temperature of the human body. On this scale, the freezing point of water turned out to be about 32°F and the boiling point about 212°F.
1°F equals 5/9°C. To convert a temperature in °F to the Celsius scale, first subtract 32° and then multiply by 5/9. In the other direction, to convert a temperature in °C to the Fahrenheit scale, multiply by 9/5 and then add 32°. The unit was defined by the German physicist Fahrenheit.

Flow phenomena are intrinsic processes in the human body. Organs like the heart, the brain or the kidneys need large amounts of blood and the blood flow varies depending on their degree of activity. Magnetic resonance imaging has a high sensitivity to flow and offers accurate, reproducible, and noninvasive methods for the quantification of flow. MRI flow measurements yield information of blood supply of of various vessels and tissues as well as cerebro spinal fluid movement.
Flow can be measured and visualized with different pulse sequences (e.g. phase contrast sequence, cine sequence, time of flight angiography) or contrast enhanced MRI methods (e.g. perfusion imaging, arterial spin labeling).
The blood volume per time (flow) is measured in: cm3/s or ml/min. The blood flow-velocity decreases gradually dependent on the vessel diameter, from approximately 50 cm per second in arteries with a diameter of around 6 mm like the carotids, to 0.3 cm per second in the small arterioles.

Different flow types in human body:
See also Flow Effects, Flow Artifact, Flow Quantification, Flow Related Enhancement, Flow Encoding, Flow Void, Cerebro Spinal Fluid Pulsation Artifact, Cardiovascular Imaging and Cardiac MRI.

(F) The number of repetitions of a periodic process per unit time. It is related to angular frequency, w, by f = w/2p. In electromagnetic radiation, it is usually expressed in units of Hertz (Hz), where 1 Hz = 1 cycle per second.

(G) An older unit of flux density. The currently preferred SI unit is the tesla (T).
Definition: 1 gauss is defined as 1 line of flux per cm². The Earth's magnetic field is approximately one half gauss to one gauss, depending on location. For the large magnetic fields used by MRI, the unit gauss (G) has been replaced by the more practical unit tesla (T), where 1 T = 10 000 G.