Tissue Differentiation in MR signal



Signal in MR images is high or low (bright or dark), depending on the pulse sequence used, and the type of tissue in the image. The following tables are a general guide to how tissue appears on T1- or T2- weighted images.

Dark on T1-weighted image:
  • increased water, as in edema, tumor, infarction, inflammation, infection, hemorrhage (hyperacute or chronic)
  • low proton density, calcification
  • flow void

Bright on T1-weighted image:
  • fat
  • subacute hemorrhage
  • melanin
  • protein-rich fluid
  • slowly flowing blood
  • paramagnetic substances: gadolinium, manganese, copper
  • calcification (rarely)
  • laminar necrosis of cerebral infarction

Bright on T2-weighted image:
  • increased water, as in edema, tumor, infarction, inflammation, infection, subdural collection
  • methemoglobin (extracellular) in subacute hemorrhage

Dark on T2- weighted image:
  • low proton density, calcification, fibrous tissue
  • paramagnetic substances: deoxyhemoglobin, methemoglobin (intracellular), iron, ferritin, hemosiderin, melanin
  • protein-rich fluid
  • flow void

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