MRI of the placenta

While ultrasound remains the primary imaging technique for placental evaluation, magnetic resonance imaging plays an adjunctive role in the setting of inconclusive sonographic findings. Accurate interpretation of placental MR imaging examinations requires knowledge of patient risk factors and sonographic findings in addition to familiarity with the expected normal and variant placental appearances at various stages of development. Multiplanar T2-weighted single-shot turbo/fast spin-echo sequences (e.g., rapid acquisition with relaxation enhancement [RARE] sequences such as half-Fourier acquisition single-shot turbo spin-echo [HASTE]) excel at revealing the internal structure of the placenta and underlying myometrium in addition to demonstrating fetal anatomy. When augmented with additional T1-weighted, T2-weighted, and/or balanced steady state free precession sequences, MRI becomes a powerful tool for detecting and characterizing clinically significant variants, hematomas, invasion, and neoplasms of the placenta.