How is a Morton's neuroma seen on MRI?

As a teardrop-shaped soft-tissue mass in the intermetatarsal space (commonly the 2nd–3rd), typically low signal on T2 because it is fibrous. A short-axis fat-suppressed sequence perpendicular to the metatarsals shows it best, often with an adjacent intermetatarsal bursa.

Why does foot MRI need STIR rather than spectral fat-sat?

The foot is curved and sits away from the magnet isocentre, so the local field is inhomogeneous and frequency-based fat suppression fails patchily. STIR suppresses fat by inversion time, staying uniform across the forefoot.

How are the imaging planes referenced in the foot?

To the metatarsal shafts: a short-axis plane perpendicular to them for the plantar plate and interdigital nerves, and a long-axis plane parallel to them for the plate insertion and ray alignment.

Resources/Protocols

Foot / forefoot

A small, curved region where fat suppression fails easily and the targets — the plantar plate, a Morton's neuroma, a stress fracture — are millimetres across. Planning to the metatarsal axis and keeping the fat dark is the whole task.

Protocols/Musculoskeletal

When this study is used

Forefoot pain — plantar plate tear, Morton's neuroma or metatarsalgia.
Stress fracture or osteomyelitis.
Midfoot or Lisfranc injury; soft-tissue mass.

Patient & coil positioning

Feet-first supine in a dedicated foot/ankle coil; forefoot centred and flat.
Strap the foot; even toe motion blurs the fine structures.
Small FOV and high matrix; the plantar plate and interdigital nerves are tiny.

Localizer

Three-plane localizer covering the target region (forefoot, midfoot or whole foot as indicated).

Sequence planning

Each sequence below lists how the slice group is positioned — the reference line it follows, its coverage, and why it earns its place in the protocol. Plan against the localizer, not by eye.

Short-axis (axial to metatarsals) PD/T2 fat-sat

Short-axis

Planning — Perpendicular to the metatarsal shafts through the region of interest.

Why — Plantar plate, interdigital (Morton's) neuromas and intermetatarsal bursae in cross-section.

Long-axis (sagittal to metatarsals) PD/T2 fat-sat

Long-axis

Planning — Parallel to the metatarsal shafts.

Why — Plantar-plate insertion, tendons and joint alignment along the ray.

Coronal (dorsoplantar) STIR

Coronal / dorsoplantar

Planning — Across the forefoot.

Why — Marrow oedema — stress fracture, osteomyelitis — with suppression robust to the curved foot.

T1

Any

Planning — Matched coverage.

Why — Anatomy, marrow replacement and fracture lines.

Representative parameters

Ranges, not commandments — field strength, coil and vendor move the numbers. What must not move is understanding why each sits where it does.

Sequence	Matrix / FOV	Notes
Short-axis PD FS	320–384 / 10–14 cm	Plantar plate, Morton's neuroma
Long-axis PD FS	320 / 12–16 cm	Plate insertion, alignment
STIR	256–320 / 12–16 cm	Marrow oedema; robust suppression
T1	320 / 12–16 cm	Anatomy, fracture

Artifacts & how to fix them

Artifact	Typical cause	Mitigation
Fat-sat failure	Curved foot, air interface	Re-shim on the forefoot; STIR; Dixon
Low resolution	FOV too large for tiny targets	Small FOV, high matrix
Toe motion	Involuntary movement	Strap the foot; raise NEX
Magic angle	Curved tendon at 55°	Compare on T2 (long TE)

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
Plantar plate tear	Short + long-axis PD FS	Fluid/discontinuity at the plantar-plate insertion (usually 2nd MTP)
Morton's neuroma	Short-axis PD FS / T1	Teardrop soft-tissue mass in the intermetatarsal space, dark on T2
Stress fracture	STIR + T1	Bright marrow oedema on STIR; a dark fracture line on T1

Review checklist

Short-axis perpendicular to the metatarsals for the plantar plate and neuromas.
Long-axis along the ray for the plate insertion.
Fat suppression uniform (or STIR) over the curved forefoot.
Small FOV and high matrix for the fine structures.

Mistakes that cost repeats

Fat-sat failing over the curved foot and hiding oedema.
FOV too large to resolve a small neuroma or plate tear.
Toe motion blurring the study.
Planes not referenced to the metatarsal axis.

Common questions

How is a Morton's neuroma seen on MRI?: As a teardrop-shaped soft-tissue mass in the intermetatarsal space (commonly the 2nd–3rd), typically low signal on T2 because it is fibrous. A short-axis fat-suppressed sequence perpendicular to the metatarsals shows it best, often with an adjacent intermetatarsal bursa.
Why does foot MRI need STIR rather than spectral fat-sat?: The foot is curved and sits away from the magnet isocentre, so the local field is inhomogeneous and frequency-based fat suppression fails patchily. STIR suppresses fat by inversion time, staying uniform across the forefoot.
How are the imaging planes referenced in the foot?: To the metatarsal shafts: a short-axis plane perpendicular to them for the plantar plate and interdigital nerves, and a long-axis plane parallel to them for the plate insertion and ray alignment.

Try it in ScanFlo: Plan a short-axis stack perpendicular to the metatarsals through the forefoot and look in the intermetatarsal spaces. That plane is what reveals a Morton's neuroma or a plantar-plate tear the routine views would miss.

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