The act of maintaining a constant phase relationship between oscillating waves or rotating objects.

A term describing the degree, to which precessing nuclear spins are synchronous.

Excitation by a RF pulse can be considered as creating a transition (or 'coherence') between different energy levels. Formally, transitions are only allowed between states of the spin system differing in spin quantum number by one unit (single quantum coherence), but multiple RF pulses can act in cascade and produce multiple quantum coherence. Only single quantum coherence produces a directly observable signal, requiring indirect observation of multiple quantum frequencies.

(CE FLASH) A fast T2 weighted imaging sequence utilizing refocused transverse coherence.

See Contrast Enhanced Echo Sequence.

Loss of coherence = Loss of transverse magnetization.