Final answer:
Transvaginal ultrasound (TVU) is used to diagnose and follow ovarian cysts.
Step-by-step explanation:
The primary imaging technique used to diagnose and follow ovarian cysts is transvaginal ultrasound (TVU). This procedure involves inserting a probe into the vagina to obtain detailed images of the ovaries. TVU is considered safe, non-invasive, and does not involve the use of radiation. It provides a clear view of the size, location, and characteristics of the cysts.