(RIS) Radiology information system means a computer system that stores and processes the information for a radiology department and can be linked to the hospital information system.
The principal purpose of a RIS consists of taking over the general functions of the administration inclusive planning, monitoring and communication of all data regarding patients and its investigations in the radiology. The correct images should reach, at the correct time, the correct users. For this reason the RIS must contain a workflow management in order to simplify and steer the data flow at the individual view stations or devices (laser cameras etc.). The Radiology Information System is optimally complemented with a Picture Archiving and Communication System (PACS).

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.

Resolution is a function of slice thickness, field of view (FOV) and matrix size. The resolution in plane is a function of FOV / matrix size.

Quick Overview

Artifacts either by distorting the k-space trajectory (i.e. due to imperfect shimming) or as a consequence of the reduced bandwidth in the phase encode direction, commonly with EPI sequences.
While a standard spin warp-based sequence has an infinitely large bandwidth in the phase encode direction (about 1 or 2 kH), the bandwidth in EPI is related to the time between the gradient echoes (about a millisecond).
Hence even small frequency offsets can result in significant shifts of the signal in the phase encoding direction. Segmentation can introduce ghosting if there are significant difference in the amplitude and phase of the signal. This can be a particular problem when trying to acquire the segments in rapid succession.

Suitable choices of excitation schemes and/or subsequent correction can help to reduce this artifact. The signal from fat can easily be offset by a large fraction of the FOV, and must be suppressed. The effect of frequency offsets can be reduced by collecting data with more than one excitation, which effectively increases the bandwidth in the phase encoding direction.

Quick Overview

Uneven intensity or brightness may occasionally be noted on high field MRI e.g. of the brain. There are various causes of localized inhomogeneous brightness across the MRI images such as improper tuning of the RF transceiver, unbalanced deposition of the RF energy due to incorrect geometry and localized attenuation due to positioning or anatomical variants.

Tuning of the RF transceiver, a homogeneity correction filter and better positioning of the scanned object and/or coil in the scanner.