Stroke MRI protocol
A time-critical protocol built around diffusion. The sequence order is the protocol: answer 'is there an infarct, how old, and is there blood?' in the first few minutes.
By the ScanFlo Editorial Team · Updated
In this section · Protocols
When this study is used
- Acute focal neurological deficit within the treatment window.
- Suspected transient ischaemic attack for tissue confirmation.
- Distinguishing acute infarct from mimics (seizure, migraine, mass).
Patient & coil positioning
- Head-first supine in a head coil; minimise setup time, because this is a time-critical patient.
- Immobilise firmly; acute-stroke patients often cannot cooperate with breath-holds or stillness.
- Centre on the glabella; confirm the alarm ball is reachable.
Localizer
Three-plane localizer, then straight into diffusion. In acute stroke the survey exists only to plan the DWI, which must be acquired before anything else in case the patient deteriorates.
Sequence planning
For each sequence below you get the reference line the slice group follows, how much it covers, and why the sequence is in the protocol at all. Plan against the localizer, not by eye.
Axial DWI + ADC
AxialPlanning: AC–PC angulation, whole brain. Scanned first, always. Read the ADC map alongside to separate true restriction from T2 shine-through.
Why: Detects and ages the infarct. Restricted diffusion appears within minutes and evolves predictably.
Axial SWI or T2* GRE
AxialPlanning: Match the DWI coverage; low flip angle.
Why: Excludes haemorrhage before any thrombolysis decision. This is the single most important safety sequence here.
Axial FLAIR
AxialPlanning: AC–PC angulation. The DWI–FLAIR mismatch estimates infarct age when onset time is unknown.
Why: A hyperacute infarct is bright on DWI but not yet on FLAIR; their mismatch brackets the onset window.
Intracranial MRA (TOF)
Axial slabPlanning: Time-of-flight slab over the circle of Willis; reconstruct MIPs in multiple projections.
Why: Large-vessel occlusion assessment without contrast, guiding thrombectomy decisions.
Perfusion (if available)
AxialPlanning: Dynamic susceptibility contrast over the whole brain during a bolus.
Why: Estimates the ischaemic penumbra, the salvageable tissue around the infarct core.
Representative parameters
Treat these as ranges. Field strength, coil and vendor all move the numbers. What must not move is understanding why each sits where it does.
| Sequence | TR (ms) | TE (ms) | Slice / gap | Notes |
|---|---|---|---|---|
| DWI (EPI) | 3000–6000 | 60–100 | 4–5 mm / 10–20% | b = 0 and 1000 s/mm²; read with ADC |
| SWI / T2* | 600–800 | 15–25 | 3–4 mm | Low flip; haemorrhage exclusion |
| FLAIR | 8000–11000 | 80–140 | 4–5 mm / 10–30% | DWI–FLAIR mismatch for age |
| TOF MRA | 20–30 | 3–7 | 0.6–1 mm | 3D slab; MIP reconstruction |
Artifacts & how to fix them
| Artifact | Typical cause | Mitigation |
|---|---|---|
| EPI distortion | Susceptibility at skull base / sinuses on DWI | Higher bandwidth; parallel imaging; RESOLVE DWI |
| T2 shine-through | Bright T2 lesion mimicking restriction | Always confirm with the ADC map |
| Motion | Uncooperative acute patient | Fastest sequences first; firm immobilisation |
| TOF saturation | In-plane slow flow appearing occluded | Thin slabs; check source images as well as the MIP |
What am I looking at?
You are not reporting the study, but recognising pathology helps you keep it in the field of view and know when to add a sequence or contrast. How the common findings read on the console:
| Finding | Sequence to check | How it reads |
|---|---|---|
| Acute infarct core | DWI + ADC | Bright on DWI, dark on ADC |
| Haemorrhage | SWI / T2* | Blooming dark signal; excludes thrombolysis |
| Large-vessel occlusion | TOF MRA | Abrupt cut-off of the vessel on source and MIP |
| Penumbra | Perfusion | Region of reduced flow larger than the DWI core |
Review checklist
- DWI acquired and reviewed before any treatment decision.
- Haemorrhage explicitly excluded on SWI/T2*.
- Restriction confirmed as dark on ADC, not T2 shine-through.
- DWI–FLAIR mismatch documented when onset time is unknown.
- MRA source images reviewed as well as the MIP.
Mistakes that cost repeats
- Reading DWI without the ADC map and calling shine-through an infarct.
- Delaying diffusion behind anatomical sequences in a deteriorating patient.
- Judging vessel patency from the MIP alone, where slow flow can look occluded.
- Skipping the haemorrhage-exclusion sequence before thrombolysis.
Common questions
- Why is DWI acquired first in stroke imaging?
- Restricted diffusion appears within minutes of infarction and the patient may deteriorate at any moment. Diffusion answers the decisive question, so it is scanned before any anatomical sequence.
- What is the DWI–FLAIR mismatch?
- A hyperacute infarct is already bright on DWI but not yet on FLAIR. When present, that mismatch indicates the infarct is likely within a few hours of onset, which helps when the exact onset time is unknown.
- Why exclude haemorrhage before treatment?
- Thrombolysis in the presence of haemorrhage is dangerous. SWI or T2* is the safety sequence that rules blood in or out before any clot-busting decision.
Try it in ScanFlo: Load a diffusion case and scan the DWI, then generate the ADC map. Practise reading them together until 'bright on DWI, dark on ADC' becomes automatic. That pairing is what separates a real infarct from T2 shine-through. See ScanFlo MRI →