During a transvaginal ultrasound, your doctor or a medical technician inserts a wandlike device (transducer) into your vagina while you lie on your back on an exam table. The transducer emits sound waves that generate images of your pelvic organs, including your ovaries. On an ultrasound image (inset), a polycystic ovary shows many follicles. Each dark circle on the ultrasound image represents a fluid-filled follicle in the ovary. Your doctor may suspect PCOS if you have 20 or more follicles in each ovary.