Short name: Gd-DTPA, generic name: Gadopentetate dimeglumine, chemical compound: Gadolinium-diethylenetriaminepentaacetic acid
Gadopentetate dimeglumine was introduced in 1981, as the first paramagnetic MRI contrast agent (ionic). The Gd-induced dipole dipole interactions lead to shortening of T1, which results in contrast enhancement on T1 weighted images. The used metal ion Gd3+ (gadolinium) is toxic, and therefore bound in the renally excreted DTPA chelate, a very stable complex. The Gd-complex also induce susceptibility effects, as a result of the magnetic field gradient between the contrast agent in the blood vessels and the surrounding tissue, that lead to shortening of T2 or T2*.
Following intravenous administration, the compound is distributed rapidly in the extracellular space and is eliminated unchanged by glomerular filtration via the kidneys. Up to 6 hours, post injection an average of 83% of the dose is eliminated renal.

See also Magnevist®, Gadolinium and Contrast Agents.

This term is commonly used for a particular kind of gradient coil, commonly used to create magnetic field gradients perpendicular to the main magnetic field. A golay coil (a special kind of saddle coils) produces a linear gradient in the x and y axes that requires wires running along the bore of the magnet. Such a coil produces a very linear field, but the linearity is lost rapidly away from the central plane. A number of pairs with different axial separations can be used to improve this.

Current carrying coils designed to produce a desired magnetic field gradient (so that the magnetic field will be stronger in some locations than others).
Proper design of the size and configuration of the coils is necessary to produce a controlled and uniform gradient. Three paired orthogonal current-carrying coils located within the magnet that are designed to produce desired gradient magnetic fields, which collectively and sequentially are superimposed on the main magnetic field (B0) so that selective spatial excitation of the imaging volume can occur.
Gradients are also used to apply reversal pulses in some fast imaging techniques. Gradient coils in general vary the main magnetic field, so that each signal can be related to an exact location. The gradient coil configuration for the z-axis consists of e.g., Helmholtz pair coils, and of paired saddle coils for the x- and y-axis.

See also the related poll result: 'Most outages of your scanning system are caused by failure of'

Gradient moment nulling used as motion artifact suppression technique (MAST) reduces constant velocity motion distortion in standard spin echo or gradient echo pulse sequences. It is an adjustment to zero at the echo time (TE) of the net moments of the amplitude of the waveform of the magnetic field gradients with time. The zeroth moment is the area under the curve. The first moment is the 'center of gravity' etc.
The aim is to minimize the phase shifts acquired by the transverse magnetization of excited nuclei moving along the gradients (including the effect of refocusing radio frequency pulses), particularly for the reduction of image artifacts due to motion.

(GMR) The application of strategic gradient pulses can compensate the objectionable spin phase effects of flow motion. That means the reducing of flow effects, e.g. gradient moment nulling of the first order of flow. The simplest velocity-compensated pulse sequence is the symmetrical second echo of a spin echo pulse sequence.
Gradient field changes can be configured in such a way that during an echo the magnetization signal vectors for all pixels have zero phase angle independent of velocities, accelerations etc. of the measured tissue. E.g. the adjustment to zero at the time TE of the net moments of the amplitude of the waveform of the magnetic field gradients with time. The zeroth moment is the area under the curve, the first moment is the 'center of gravity' etc. The aim is to minimize the phase shifts acquired by the transverse magnetization of excited nuclei moving along the gradients (including the effect of refocusing RF pulses), particularly for the reduction of image artifacts due to motion.
Also called Flow Compensation (FC), Motion Artifact Suppression Technique (MAST), Flow motion compression (STILL), Gradient Rephasing (GR), Shimadzu Motion Artifact Reduction Technique (SMART).