MRI interpretation
T1 v T2 images

Key points

  • On T1 images FAT is white
  • On T2 images both FAT and WATER are white

It’s all about FAT and WATER

The two basic types of MRI images are T1-weighted and T2-weighted images, often referred to as T1 and T2 images.

The timing of radiofrequency pulse sequences used to make T1 images results in images which highlight fat tissue within the body.

The timing of radiofrequency pulse sequences used to make T2 images results in images which highlight fat AND water within the body.

So, this makes things easy to remember.

T1 images – 1 tissue type is bright – FAT

T2 images – 2 tissue types are bright – FAT and WATER

T1-weighted image – Anatomy (spine)

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T1-weighted image – Anatomy (spine)

  • T1 images can be thought of as a map of proton energy within fatty tissues of the body
  • Fatty tissues include subcutaneous fat (SC fat) and bone marrow of the vertebral bodies
  • Cerebrospinal fluid (CSF) contains no fat – so it appears black on T1-weighted images

T2-weighted image – Anatomy (spine)

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T2-weighted image – Anatomy (spine)

  • T2 images are a map of proton energy within fatty AND water-based tissues of the body
  • Fatty tissue is distinguished from water-based tissue by comparing with the T1 images – anything that is bright on the T2 images but dark on the T1 images is fluid-based tissue
  • For example, the CSF is white on this T2 image and dark on the T1 image above because it is free fluid and contains no fat
  • Note that the bone cortex is black – it gives off no signal on either T1 or T2 images because it contains no free protons

T1 weighted image – Pathology (spine)

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T1 weighted image – Pathology (spine)

  • Loss of the normal high signal in the bone marrow indicates loss of normal fatty tissue and increased water content
  • Abnormal low signal on T1 images frequently indicates a pathological process such as trauma, infection, or cancer

T2 weighted image – Pathology (spine)

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T2 weighted image – Pathology (spine)

  • The same areas are whiter than usual on this T2 image indicating increased water content
  • Abnormal brightness on a T2 image indicates a disease process such as trauma, infection, or cancer
  • This patient had multiple myeloma