Ultrasound and magnetic resonance imaging of pelvic masses.

Magnetic resonance imaging (MRI) is a complementary imaging modality to ultrasound in the evaluation of pelvic masses. Indications for MRI include differentiating a uterine from an adnexal mass when the ultrasound is inconclusive, establishing the presence of blood in a "simple" appearing cyst and demonstrating fat within a mass that is sonographically suspicious of a benign cystic teratoma.