From ISOL Technology

'Next generation MRI system 1.5T CHORUS developed by ISOL Technology is optimized for both clinical diagnostic imaging and for research development.
CHORUS offers the complete range of feature oriented advanced imaging techniques- for both clinical routine and research. The compact short bore magnet, the patient friendly design and the gradient technology make the innovation to new degree of perfection in magnetic resonance.'

Quick Overview

The entry slice phenomenon arise in MRI when blood with unsaturated spins flows in the observed slice(s). These spins will emit a strong signal, because of their unsaturated status (flow related enhancement). The number of slices affected depends on the flow velocity and the slice thickness; the direction of flow determines which slices are affected. Time of Flight MRA is based on this entry slice phenomenon.

See also Flow Compensation, Flow Related Enhancement, Artifact Overview and Artifacts Reduction Index.

(FAT SAT) A specialized technique that selectively saturates fat protons prior to acquiring data as in standard sequences, so that they produce a negligible signal. The presaturation pulse is applied prior to each slice selection. This technique requires a very homogeneous magnetic field and very precise frequency calibration.
Fat saturation does not work well on inhomogeneous volumes of tissue due to a change in the precessional frequencies as the difference in volume affects the magnetic field homogeneity. The addition of a water bag simulates a more homogeneous volume of tissue, thus improving the fat saturation. Since the protons in the water bag are in motion due to recent motion of the bag, phase ghosts can be visualized.
Fat saturation can also be difficult in a region of metallic prosthesis. This is caused by an alteration in the local magnetic field resulting in a change to the precessional frequencies, rendering the chemical saturation pulses ineffective.

See also Fat Suppression, and Dixon.

Quick Overview
Please note that there are different common names for this artifact.

Flow effects in MRI produce a range of artifacts, e.g. intravascular signal void by time of flight effects; turbulent dephasing and first echo dephasing, caused by flowing blood.
Through movement of the hydrogen nuclei (e.g. blood flow), there is a location change between the time these nuclei experience a radio frequency pulse and the time the emitted signal is received (because the repetition time is asynchronous with the pulsatile flow).
The blood flow occasionally produces intravascular high signal intensities due to flow related enhancement, even echo rephasing and diastolic pseudogating. The pulsatile laminar flow within vessels often produces a complex multilayered band that usually propagates outside the head in the phase encoded direction. Blood flow artifacts should be considered as a special subgroup of motion artifacts.

Artifacts can be reduced by reduction of phase shifts with flow compensation (gradient moment nulling), suppression of the blood signal with saturation pulses parallel to the slices, synchronization of the imaging sequence with the heart cycle (cardiac triggering) or can be flipped 90° by swapping the phase//frequency encoding directions.

See also Flow Related Enhancement and Flow Effects.

Quick Overview

Ghosting artifacts are in the most cases caused by movements (e.g., respiratory motion, bowel motion, arterial pulsations, swallowing, and heartbeat) and appear in the phase encoding direction.

Ghosting artifacts can be reduced by respiratory and cardiac triggering, the use of breath holding pulse sequences, flow compensation or presaturation pulses, depending on their origin. To reduce bowel motion also pharmaceuticals, such as glucagon or scopolamine are useful. This will decrease artifacts from both peristalsis and breathing.

See also Motion Artifact, Phase Encoded Motion Artifact, Cardiac Motion Artifact, and Artifact Reduction - Motion.