A gradient echo is generated by using a pair of bipolar gradient pulses. The gradient field is negatively pulsed, causing the spins of the xy-magnetization to dephase. A second gradient pulse is applied with the opposite polarity. During the pulsing, the spins that dephased begin to rephase and generate a gradient echo.
Spoiling can be accomplished by RF or a gradient. The incoherent RF spoiled type of a gradient echo sequence use a continuous shifting of the RF pulse to spoil the residual transverse magnetization. The phase of the RF excitation and receiver channel are varied pseudo randomly with each excitation cycle to prevent the xy magnetization from achieving steady state. T2* does not dominate image contrast, so T1 and PD weighting is practical. This method is effective and can be used to achieve a shorter TR, due to a lack of additional gradients. Spoiling eliminates the effect of the remaining xy-magnetization and leads to steady state longitudinal magnetization. These sequences can be used for breath hold, dynamic imaging and in cine and volume acquisitions.

The sequential collection of raw data from multiple excitations such that each excitation samples multiple lines or curvilinear paths in k-space.

(MR) Resonance phenomenon resulting in the absorption and/or emission of electromagnetic energy by nuclei (for that reason also nuclear magnetic resonance) or electrons in a static magnetic field, after excitation by a suitable RF magnetic field.
The peak resonance frequency is proportional to the magnetic field, and is given by the Larmor equation. Only unpaired electrons or nuclei with a spin exhibit magnetic resonance. The absorption or emission of energy by atomic nuclei in an external magnetic field after the application of RF excitation pulses using frequencies, which satisfy the conditions of the Larmor equation.
The magnetic resonance phenomenon may be used in one of these ways:
By manipulation of the external field (application of gradient fields), the resonance frequency can become dependent on spatial location, and hence images may be generated (MRI).
The effect of the electron cloud in any atom or molecule is to slightly shield the nucleus from the external field, thus giving any chemical species a characteristic frequency. This gives rise to 'spectra' where nuclei in a molecule give rise to specific signals, thus facilitating the detection of individual chemicals by means of their frequency spectra (MRS)

(MLSI) Variations of sequential line imaging techniques that can be used if selective excitation methods that do not affect adjacent lines are employed. Adjacent lines are imaged while waiting for relaxation of the first line toward equilibrium, which may result in decreased image acquisition time. A different type of MLSI uses simultaneous excitation of two or more lines with different phase encoding followed by suitable decoding.

(PS) Excitation technique applying repeated RF pulses in times comparable to or shorter than T1. Incomplete T1 relaxation leads to reduction of the signal amplitude; there is the possibility of generating images with increased contrast between regions with different relaxation times.
Although partial saturation is also commonly referred to as saturation recovery, that term should properly be reserved for the particular case of partial saturation in which recovery after each excitation effectively takes place from true saturation. A GRE sequence where α = 90° is identical to the partial saturation or saturation recovery pulse sequence.
It does not directly produce images of T1. However, since the measured signal will depend on T1, the method generates contrast between regions with different relaxation times. If T2 and/or T2 effects are minimized through the use of a short echo time TE, the result is a T1 weighted image. It is not a T1 image due to the possible presence of spin density and T2 effects as well as the nonlinear dependence on T1.
The change in signal from a region resulting from a change in the interpulse time, TR, can be used to calculate T1 for the region.