On MRI, adenomyosis is best characterised by which finding?

• A High-signal intensity foci within the junctional zone with overall JZ thickness > 12 mm ✓
• B Diffuse uterine enlargement with heterogeneous T2-signal and JZ thickness < 8 mm
• C Well-defined hypointense pseudocapsule surrounding intramural masses
• D Bright T1 fluid-fluid levels in adnexal masses

Explanation

Adenomyosis on MRI is characterised by thickening of the junctional zone (JZ) — the inner myometrial layer appearing dark on T2. Criteria include: JZ maximum thickness ≥ 12 mm (diagnostic), or 8–12 mm (borderline/suspicious). High-signal T2 'spots' within the junctional zone represent ectopic endometrial glands and stroma. A JZ < 8 mm essentially excludes adenomyosis. T1-bright foci indicate hemorrhagic foci (old blood) within adenomyotic deposits.

Reference: Shaw's Textbook of Gynaecology, 17th ed.

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