MRI Sequences

Strokes on MRI

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HYPER-ACUTE
ACUTE
SUBACUTE (>48h)
CHRONIC
T1
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T1+c
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T2
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FLAIR
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bright
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Hemorrhage on MRI

T1

  • short T1 = High signal
BRIGHT
DARK
fat
melanin
Onyx
subacute blood (>48 hr)
CSF
most pathology
 

T1+c

Gadolinium generally contraindicated for GFR < 30 and relatively contraindicated for 30-60 ml/min

T2

T2 FLAIR (FLuid-Attenuated Inversion Recovery)

  • T2 minus CSF
  • good for demonstrating CSF abnormalities
  • FLAIR is best sequence for detecting acute SAH
BRIGHT
DARK
MS plaques
tumors
edema
encephalomalacia
gliosis
acute infarcts
(failure of T2 suppression)

Diffusion Tensor Imaging (DTI)

  • uses difference in diffusion between axons parallel to white matter tracts and perpendicular to their course
 

MRA (Time of flight)

  • despite common misconception, this is a non-contrast study
  • uses flow-related enhancement techniques (2D time of flight)
  • usually used for intracranial vessels

Miscellaneous

  • aneurysm clips 1990 and after are MRI compatible