MRI Basic

Intensity Pattern

Mono

Compare intensity to grey matter.

T1

• Hypo T1: fluid (chronic lesion)

• Hyper T1:

  • Fat (except T1FS)
  • Protein (depend on content)
  • Blood (early & late subacute)
  • Paramagnetic, Melanin

T2

• Hyper T2: fluid (CSF) > fat

Combined

• Hypo T1 & T2: Air, Flow void (high-flow vessel), Calcification

• Iso T1 & T2: Muscle

• Hypo T1 + Hyper T2: fluid

Blood Signal

Figure 1: MRI Signal of Aging Blood [1] and blog post

	Time	T1	T2
Hyperacute	< 12 hr	Isointense	Bright
Acute	12 hr - 2 days	Isointense	Dark
Early subacute	2 - 7 days	Bright	Dark
Late subacute	1 wks - 2 mos	Bright	Bright
Chronic	> 2 mos	Dark	Dark

References

[1]

W.G. Bradley, MR appearance of hemorrhage in the brain, Radiology. 189 (1993) 15–26. https://doi.org/10.1148/radiology.189.1.8372185.