Magnetic susceptibility artifact

Magnetic susceptibility artifacts (or just susceptibility artifact) refer to a variety of MRI artifacts that share distortions or local signal change due to local magnetic field inhomogeneities from a variety of compounds. 

They are especially encountered while imaging near metallic orthopedic hardware or dental work, and result from local magnetic field inhomogeneities introduced by the metallic object into the otherwise homogeneous external magnetic field B0. These local magnetic field inhomogeneities are a property of the object being imaged, rather than of the MRI unit. 

A common susceptibility related artefact, deliberately sought to make small lesions more conspicuous, is the blooming artefact

Types of magnetic susceptibility

In terms of magnetic susceptibility, most materials can be classified as diamagnetic, paramagnetic, superparamagnetic, or ferromagnetic.

Diamagnetic

Water is considered (weakly) diamagnetic.

Paramagnetic

Paramagnetic materials, which have unpaired electrons, concentrate local magnetic forces and thus increase the local magnetic field, i.e. have increased magnetic susceptibility.

Superparamagnetic

Superparamagnetic materials contain particles with a much stronger magnetic susceptibility than that of paramagnetic materials, e.g. SPIO (superparamagnetic iron oxide) has been used in liver imaging.

Ferromagnetic

Ferromagnetic materials contain large solid or crystalline aggregates of molecules with unpaired electrons exhibit “magnetic memory,” by which a lingering magnetic field is created after their exposure to an external magnetic field. Examples of ferromagnetic metals include iron, nickel, and cobalt, all of which distort magnetic fields, thereby causing severe artifacts on MR images.


MRI physics
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Article Information

rID: 18971
Section: Physics
Tag: refs
Synonyms or Alternate Spellings:
  • Magnetic susceptibility artefact
  • Magnetic susceptibility artefacts
  • Magnetic susceptibility artifacts
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