Why is sagittal 3D FLAIR the main MS sequence?

MS plaques often sit in the corpus callosum and radiate perpendicular to the ventricles as 'Dawson's fingers'. These are best seen from the side with CSF suppressed, which is exactly what a sagittal FLAIR provides. A 3D acquisition also reformats into every plane.

Why give contrast in an MS study?

Gadolinium enhancement marks an actively inflamed, demyelinating lesion. It separates new, active plaques from old, chronic ones, and that information guides treatment decisions.

Should the cord be imaged in suspected MS?

When clinically indicated, yes. Cord plaques can confirm dissemination in space and change both diagnosis and prognosis, so cervical cord imaging is often added.

Multiple sclerosis MRI protocol

The demyelination protocol. MS plaques hide in the corpus callosum and are best seen from the side with CSF suppressed. So the sequence that matters is sagittal 3D FLAIR, with contrast to separate active lesions from old.

By the ScanFlo Editorial Team · Updated 12 October 2026

In this section · Protocols

Protocols/Brain

When this study is used

Suspected demyelination or first clinical demyelinating event.
Known MS: monitoring disease activity or treatment response.
Distinguishing active from chronic lesions.

Patient & coil positioning

Head-first supine in a head coil, straight and immobilised.
Centre on the glabella; the 3D sequences are motion-sensitive over a long acquisition.
Warn the patient the exam is longer than a routine brain and stillness matters throughout.

Localizer

Three-plane localizer plus the routine brain survey (DWI, T2, T1). The dedicated sequence is a sagittal 3D FLAIR, reformatted into axial and coronal planes.

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.

Sagittal 3D FLAIR

Sagittal / reformatted

Planning: Whole-brain isotropic volume aligned to the midline; reformat axial and coronal from it.

Why: Dawson's fingers (flame-shaped periventricular lesions perpendicular to the ventricles) and callosal plaques, best profiled sagittally.

Axial T2 / PD

Axial

Planning: AC–PC angulation, whole brain.

Why: Lesion load across the hemispheres and infratentorial disease.

Axial T1 pre/post-contrast

Axial

Planning: Matched pre- and post-gadolinium coverage.

Why: Enhancing lesions mark active demyelination; non-enhancing are chronic.

Sagittal cord (if indicated)

Sagittal

Planning: Extend to the cervical cord when clinically indicated.

Why: Cord plaques, which change diagnosis and prognosis.

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	Slice	Matrix	Notes
3D FLAIR	1 mm isotropic	256+	Reformat axial + coronal
T2 TSE axial	3–4 mm	320	Lesion load
T1 pre/post	3–4 mm	256	Active vs. chronic

Artifacts & how to fix them

Artifact	Typical cause	Mitigation
CSF flow on FLAIR	Pulsatile CSF mimicking lesions	Flow compensation; confirm on a second plane
Motion over long 3D scan	Patient fatigue mid-acquisition	Reassure; parallel imaging; break into shorter blocks
Incomplete fat suppression (cord)	Field inhomogeneity in the neck	STIR over spectral fat-sat for cord imaging

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
Dawson's fingers	Sagittal 3D FLAIR	Flame-shaped bright lesions perpendicular to the callosal margin
Active plaque	T1 post-contrast	Enhancing (often ring or open-ring) lesion
Chronic 'black hole'	T1 pre-contrast	Persistently dark lesion indicating axonal loss

Review checklist

Sagittal 3D FLAIR acquired and reformatted into axial and coronal.
Callosal and periventricular regions clearly profiled.
Pre- and post-contrast T1 matched slice-for-slice.
Cord imaging added when clinically indicated.

Mistakes that cost repeats

Relying on axial FLAIR alone and missing callosal Dawson's fingers.
Mistaking CSF-flow artefact for a periventricular lesion.
Unmatched pre/post-contrast coverage, so enhancement can't be judged.
Motion late in the long 3D acquisition.

Common questions

Why is sagittal 3D FLAIR the main MS sequence?: MS plaques often sit in the corpus callosum and radiate perpendicular to the ventricles as 'Dawson's fingers'. These are best seen from the side with CSF suppressed, which is exactly what a sagittal FLAIR provides. A 3D acquisition also reformats into every plane.
Why give contrast in an MS study?: Gadolinium enhancement marks an actively inflamed, demyelinating lesion. It separates new, active plaques from old, chronic ones, and that information guides treatment decisions.
Should the cord be imaged in suspected MS?: When clinically indicated, yes. Cord plaques can confirm dissemination in space and change both diagnosis and prognosis, so cervical cord imaging is often added.

Try it in ScanFlo: Acquire a sagittal FLAIR and look along the corpus callosum for flame-shaped lesions, then reformat the same 3D volume into axial and coronal. Seeing the same plaque in three planes is what confirms it is real, not an artefact. See ScanFlo MRI →

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