(REST - regional saturation technique / SAT - saturation/ Pre-Sat / spatial Pre-Sat) A specialized technique employing repeated RF excitation of structures adjacent to the ROI for the purpose of reducing or eliminating their phase effect artifacts. This presaturation can be performed on both sides parallel or perpendicular to the slice. Vascular ghosting is eliminated by saturation areas parallel (outside) to the slice plane, because flowing blood produces almost no signal. The possibility of moving presaturation (moving REST / traveling SAT) makes sequence planning and scanning comfortable.

The schematic figures of a pulse sequence timing diagram illustrate the steps of basic hardware activity that are incorporated into a pulse sequence. Time during sequence execution is indicated along the horizontal axes. Each line belongs to a different hardware component. One line is needed for the radio frequency transmitter and also one for each gradient (G_s = slice selection gradient x, G_f = phase encoding gradient y, G_f = frequency encoding gradient z, also called readout gradient).
In picture 1, a timing diagram for a 2D pulse sequence is shown.
Slice selection and signal detection are repeated in duration, relative timing and amplitude, each time the sequence is repeated. A single phase encoding component is present each time the sequence is executed.
Additional lines are added for ADC (Analog to Digital Converter) and sampling. A gradient pulse is shown as a deviation above or below the horizontal line. Simultaneous component activities such as the RF pulse and slice selection gradient are indicated as a non-zero deviation from both lines at the same horizontal position. Simple deviations from zero show constant amplitude gradient pulse. Gradient amplitudes that change during the measurement, e.g. phase encoding are represented as hatched regions.

The second picture shows a timing diagram for a 3D pulse sequence.
Volume excitation and signal detection are repeated in duration, relative timing and amplitude, each time the sequence is repeated. Two phase encoding components are present, one in the phase encoding direction and the other in slice selection direction (irrespectively incremented in amplitude) in each time the sequence is executed. A description of the comparison of hardware activity between different pulse sequences.

After RF excitation the spins will tend to return to their equilibrium distribution in which there is no transverse magnetization and the longitudinal magnetization is at its maximum value and oriented in the direction of the static magnetic field. The transverse magnetization decays toward zero with a characteristic time constant T2, and the longitudinal magnetization returns toward equilibrium with a characteristic time constant T1.

Technique of MR imaging that uses a gradient of the RF excitation field (to give a corresponding variation of the flip angle along the gradient as a means of encoding the spatial location of spins in the direction of the RF field gradient) in conjunction with a static magnetic field gradient (to give spatial encoding in an orthogonal direction). It can be considered to be a form of Fourier transformation imaging.

Sequence of RF (and gradient) pulses designed to produce saturation, typically in a selected region or set of regions, most often by the use of selective excitation followed by a spoiler pulse. Similar to some spectral suppression techniques. Can be used to reduce signal from flowing blood by saturating regions upstream from region being imaged.