Hounsfield units are frequently used as intensity for CT images.
What is used for MR images?
There are no units for MRI intensity.
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.
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)