Stroke protocol (MRI)
MRI protocol for stroke assessment is a group of MRI sequences put together to best approach brain ischemia.
CT is still the choice as the first imaging modality in acute stroke institutional protocols, not only because the availability and the easy and fast access to a CT scanner, but also due the better sensitivity for intracerebral hemorrhage (ICH) diagnosis . Some institutions also apply a quick MRI stroke protocol for code stroke patients assessment within the narrow time window for thrombolytic therapy.
Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's and referrer's preference, institutional protocols, patient factors (e.g. allergy) and time constraints.
Sequences
A good protocol involves at least:
- T1 weighted
- plane: sagittal (or volumetric 3D)
- sequence: fast-spin echo (T1 FSE) or gradient (e.g. T1 MPRAGE)
- purpose: an anatomical evaluation. Cortical laminar necrosis or pseudolaminar necrosis may be seen as a ribbon of intrinsic high T1 signal, usually after 2 weeks (although it can be seen earlier)
- T2 weighted
- plane: axial
- sequence: T2 FSE
- purpose:
- loss of normal signal void in large arteries may be visible immediately
- after 6-12 hours infarcted tissue becomes high signal
- sulcal effacement and mass effect develop and become maximal in the first few days
- FLAIR
- plane: axial
- sequence: FLAIR
- purpose:
- after 6-12 hours infarcted tissue becomes high signal
- sulcal effacement and mass effect develop and become maximal in the first few days
- diffusion-weighted imaging (DWI)
- susceptibility-weighted imaging (SWI)
- plane: axial
- sequence: susceptibility weighted imaging (ideal) or T2*
- purpose: highly sensitive in the detection of hemorrhage
- MR angiography (MRA)
- plane: axial with reconstructions
- sequence: time of flight angiography
- purpose: assess for luminal diameter and occlusions
