Quick Overview

A combination of B1 inhomogeneity, poor slice profile, and insufficient spoiler gradients between the refocusing pulse and the readout interval of a spin echo sequence results in a FID signal being detected along with the echo.
Since the FID is not phase encoded (normally the phase encoding occurs before the refocusing pulse), it is not dispersed along the phase encoding axis, but appears as a line across the center of the image.

If the problem persists, it must be addressed by a service representative.

Quick Overview

A receiver turn on artifact (not a true MR signal) appears similarly like a FID signal artifact, except that they extend into the signal-free region, while the FID (a real MR signal) is confined to the projection of the sample along the readout axis.

FID artifacts cannot occur on gradient echo images, but receiver turn on is still possible on gradient echoes.

See also FID Signal Artifact.

(PSIF) A heavily T2* weighted contrast enhanced gradient echo (mirrored FISP) technique. Because TE is relatively long, there are much flow artifacts and less signal to noise. In normal gradient echo techniques a FID-signal results after the RF pulses. This FID is rephased very fast and just before the next FID follows a spin echo signal. The SE is spoiled in FLASH sequences, but with PSIF sequences, only the SE is measured, not the FID.

(SE) The Reappearance of the MR signal after the FID has apparently died away, as a result of the effective reversal (rephasing) of the dephasing spins by techniques such as specific RF pulse sequences or pairs of field gradient pulses, applied in time shorter than or on the order of T2. Proper selection of the TE time of the pulse sequence can help to control the amount of T1 or T2 contrast present in the image. Pulse sequences of the spin echo type, usually employs a 90° pulse, followed by one or more 180° pulses to eliminate field inhomogeneity and chemical shift effects at the echo. Caused by this 180° refocusing pulse, spin echo or fast spin echo (FSE, TSE) sequences are more robust against e.g. susceptibility artifacts than sequences of the gradient echo type.

A signal to noise improvement method that is accomplished by taking the average of several FID's made under similar conditions to suppress the effects of random variations or random artifacts.