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MR Elastography Assistant

Liver MRE — quality check, ROI guidance, and the weighted-mean stiffness calculation.

1 · Was the exam done properly?

confirm each before measuring

2 · QA the tech's ROIs

ROIs are placed by the MRI tech — verify before measuring

Confirm

An ROI on each of the 4 slices, in the largest portion of liver.
Outer margin parallel to the liver edge, ≥1 cm from the capsule.
Inner margin excludes the 95% confidence crosshatch.
Each ROI larger than ~a postage stamp, with little to no checkerboard inside.
Mean and Area reported for each ROI (Min/Max/Mean/SD/Area visible).

Flag / re-measure if an ROI includes

The 95% confidence crosshatch.
Liver edge (<1 cm), fissures, gallbladder fossa, or large vessels.
Left lobe with motion artifact.
Hot spots — passive-driver or liver-dome (falsely high stiffness).
Low-amplitude / distorted waves or color-map “hot” areas.

Elastogram with a large freehand ROI following the confidence mask across most of the liver cross-section — Good — one large ROI across the biggest cross-section of liver, inside the 95% confidence mask and back from the capsule and the large vessels. 120.6 cm², mean 222 → 2.2 kPa.

Elastogram with a small ROI drawn around a single bright hot spot at the inferior liver — Flag / re-measure — a small ROI at the bottom of the liver drawn around a hot spot: 16.4 cm², mean 446 → 4.5 kPa, SD 176. It measures the hot spot, not the liver, and is not a true representation of parenchymal stiffness. Same problem for an ROI over the crosshatch or up against the capsule or a vessel.

3 · Weighted-mean stiffness

ROI Mean weighted by Area

ROI Mean	Area (cm²)

Enter the ROI Mean as shown on PACS (e.g., 208) and the Area. Weighted average = Σ(Mean × Area) ÷ Σ(Area); the result is divided by 100 to give stiffness in kPa.

— kPa

liver stiffness

Enter at least one ROI Mean and Area.

Copy to report

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Copy to impression

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Reference — QC, fibrosis thresholds, citation

Fibrosis stage thresholds (MRE at 60 Hz)

Mean stiffness	Interpretation
< 2.5 kPa	Normal
2.5 – 2.9 kPa	Normal or inflammation
2.9 – 3.5 kPa	Stage 1–2 fibrosis
3.5 – 4 kPa	Stage 2–3 fibrosis
4 – 5 kPa	Stage 3–4 fibrosis
> 5 kPa	Stage 4 fibrosis or cirrhosis

Broad categories; interpret with clinical and laboratory findings. Non-fibrotic causes of increased stiffness include acute hepatitis, acute biliary obstruction, passive hepatic congestion, infiltrative disease, and the postprandial state — most confounders raise (not lower) stiffness, so a normal value is generally reliable.

If nondiagnostic

The patient has usually already left. Discuss with the MRI leads about bringing them back for “Additional Views” (ordering instructions are in the Body folder).

Thresholds: Venkatesh SK, Ehman RL. Magn Reson Imaging Clin N Am 2014;22(3):433–446. Technique/QC/ROI: Guglielmo FF, Venkatesh SK, Mitchell DG, RadioGraphics educational review.