See Spatial Resolution.

The exchange of energy at a particular frequency between two systems; a large amplitude vibration in a mechanical or electrical system caused by a relatively small periodic stimulus with a frequency at or close to a natural frequency of the system.
Resonance is referred to as the property of an atom to absorb energy only at the Larmor frequency. The energy must also be delivered at 90° to the net magnetic vector (NMV) and main magnetic field (B0). Otherwise, no energy will be absorbed, resonance will not have occurred and an image cannot be created. In MRI systems, resonance can refer to the MR itself or to the tuning of the RF circuitry.

The frequency at which the resonance phenomenon occurs. The resonance frequency is given by the Larmor equation for MRI and is determined by the inductance and capacitance for RF circuits. An atom will only absorb external energy if that energy is delivered at precisely it's resonant frequency.
The Larmor equation states that the resonance frequency of a magnetic nucleus (the radio frequency needed to excite a nucleus to the higher spin rate) is directly proportional to the magnetic environment it experiences. Atoms such as hydrogen-1 (1H) and phosporous-31 (31P) resonate at different Larmor radio frequencies because of differences in the magnetic properties of their nuclei. The resonance frequency at 1.5 T for 31P is 25.85 MHz, for 1H, 63.86 MHz.

See also Larmor Frequency.

Either the phase due to an applied field or field inhomogeneity and generated during the time between two RF pulses, or the phase change of the RF pulse from one pulse to the next.

(ROAST) A gradient echo sequence.
See Refocused Gradient Echo Sequence and Steady State Free Precession.