MRI interpretation
What are MRI images?

Key points

  • MRI images are a map of proton energy within tissue of the body
  • On X-ray and CT images white = high density
  • On MRI images white = high signal

X-ray and CT images can be considered to be a map of density of tissues in the body; white areas on X-ray and CT images represent high density structures.

MRI images are different.

In simple terms, MRI images can be considered as a map of proton energy within tissues of the body. A variety of MRI images can be produced which emphasise different tissue types, in particular those that contain a large amount of fat or water.

Bright areas on an MRI image represent high ‘signal’ given off by protons in the body during the scanning process.

White areas on an X-ray or CT image = high density

White areas on an MRI image = high signal

CT v MRI - brain

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CT v MRI - brain

  • CT is a map of tissue density – white areas represent higher density tissues than blacker areas
  • MRI is a map of proton energy in tissues of the body – white areas represent high ‘signal’
  • Cerebrospinal fluid (CSF) is low density on CT
  • On this MRI image the CSF is white – indicating high signal

Page author: Salisbury NHS Foundation Trust UK (Read bio)

Last reviewed: September 2017