Sent (inducing, transferring) energy into the 'spinning' nuclei via radio frequency pulse, which puts the nuclei into a higher energy state. By producing a net transverse magnetization a MRI system can observe a response from the excited system.

Controlling the frequency spectrum (bandwidth) of a RF pulse (via tailoring) while imposing a magnetic field gradient on spins, such that only a desired region will have an appropriate resonant frequency to be excited.
Originally used to excite all but a desired region; now often used to select only a desired region, such as a plane, for excitation. Used without simultaneous magnetic field gradients, tailored RF pulses can be used to selectively excite a particular spectral line or group of lines. RF and gradient pulse combinations can be designed to select both spatial regions and spectral frequencies.

(NEX) How many times each line of k-space data is acquired during the scan.

See also Signal Averaging.

Energy transfer to nearby slices by the RF pulse.

See Crosstalk Artifact.

The selective excitation of spins in only a limited region of space. This can be particularly useful for spectroscopy as well as imaging. Spatial localization of the signal source may be achieved through spatially selective excitation and the resulting signal may be analyzed directly for the spectrum corresponding to the excited region. It is usually achieved with selective excitation.
Typically, a single dimension of localization can be achieved with one selective RF excitation pulse (and a magnetic field gradient along a desired direction), while a localized volume (3D) can be excited with a stimulated echo produced with three selective RF pulses whose selective magnetic field gradients are mutually orthogonal, having a common intersection in the desired region. Similar 'crossed plane' excitation can be used with selective 180° refocusing pulses and conventional spin echoes.
A degree of spatial localization of excitation can alternatively be achieved with depth pulses, e.g. when using surface coils for excitation as well as signal detection. An indirect application of selective excitation for volume-selected spectroscopy is to use appropriate combinations of signals acquired after selective inversion of different regions, in order to subtract away the signal from undesired regions.