Quick Overview

Movement of the heart causes blurring and ghosting in the images. The artifacts appear in the phase encoding direction, independent of the direction of the motion.

These artifacts can be reduced by using cardiac synchronization: triggering, gating or retrospective triggering. Maximum reduction can be achieved by using triggering in combination with flow compensation, respiratory triggering or breath hold and regional saturation techniques.

See also Motion Artifact.

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

This artifact appears as a bright spot (or zipper line) in the image center. Central point artifacts are caused by a DC offset in the hardware. MRI scanners normally offer a software compensation (DC correction, baseline correction) for prevention.

Take care for a constant temperature. If the problem increases or keeps on existing, it should be addressed to the service.

Quick Overview

Pulsatile cerebro spinal fluid flow produces ghost artifacts that are superimposed in the image.

Flow compensation should be used to reduce these artifacts. This applies an additional gradient to eliminate phase differences for both stationary and moving spins at the echo time. At TE no phase differences is measured. If flow compensation is applied and there are still flow artifacts, cardiac triggering is an additional option to reduce these artifacts.
See also Motion Artifact.

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

During frequency encoding, fat protons precess slower than water protons in the same slice because of their magnetic shielding. Through the difference in resonance frequency between water and fat, protons at the same location are misregistrated (dislocated) by the Fourier transformation, when converting MRI signals from frequency to spatial domain. This chemical shift misregistration cause accentuation of any fat-water interfaces along the frequency axis and may be mistaken for pathology. Where fat and water are in the same location, this artifact can be seen as a bright or dark band at the edge of the anatomy.
Protons in fat and water molecules are separated by a chemical shift of about 3.5 ppm. The actual shift in Hertz (Hz) depends on the magnetic field strength of the magnet being used. Higher field strength increases the misregistration, while in contrast a higher gradient strength has a positive effect. For a 0.3 T system operating at 12.8 MHz the shift will be 44.8 Hz compared with a 223.6 Hz shift for a 1.5 T system operating at 63.9 MHz.

For artifact reduction helps a smaller water fat shift (higher bandwidth), a higher matrix, an in phase TE or a spin echo technique. Since the misregistration offset is present in the read out axis the patient may be rescanned with this axis parallel to the fat-water interface. Steeper gradient may be employed to reduce the chemical shift offset in mm. Another strategy is to employ specialized pulse sequences such as fat saturation or inversion recovery imaging. Fat suppression techniques eliminate chemical shift artifacts caused by the lack of fat signal.

See also Black Boundary Artifact and Magnetic Resonance Spectroscopy.

Quick Overview

An artifact on a MR image can appear when data read off an optical disc became corrupted. There two effects can be seen.
Firstly, Bands where the intensity has been incorrectly interpreted or secondly areas, where the horizontal position of the pixels has been incorrectly displayed. It is important to be able to differentiate between artifacts caused during a MRI scan, from those caused by the associated hardware of an imaging system.

Review the hardware and store the images on a new disc.