Hounsfield units are frequently used as intensity for CT images.

What is used for MR images?

1 Answer 1


There are no units for MRI intensity.

A Comparison of Five Methods for Signal Intensity Standardization in MRI (CEUR-WS.org):

A major problem in magnetic resonance imaging (MRI) is the lack of a pulse sequence dependent standardized intensity scale like the Hounsfield units in computed tomography.

MRI sequences (Radiopedia):

When describing most MRI sequences we refer to the shade of grey of tissues or fluid with the word intensity, leading to the following absolute terms:

  • high signal intensity = white
  • intermediate signal intensity = grey
  • low signal intensity = black

Often we refer to the appearance by relative terms:

  • hyperintense = brighter than the thing we are comparing it to
  • isointense = same brightness as the thing we are comparing it to
  • hypointense = darker than the thing we are comparing it to

Annoyingly these relative terms are used without reference to the tissue being used as the comparison.

See also: Signal intensity (MR-tip.com)

  • Thank you for your answer!
    – Fernet
    Jan 8, 2019 at 12:28

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