OBJECTIVETo observe the characteristics of the physiological uptake of uterus and ovaries on 18F-fluorodeoxyglucose positron emission tomography (FDG PET).

METHODSA total of 288 PET examinations performed in 247 women (164 with malignancies, 44 with benign diseases, and 39 without remarkable abnormality) were included for analysis, and clinical follow-ups were applied for at least 10 months to exclude pelvic diseases. The menstrual statuses, menstrual cycles, and related pelvic examinations with other modalities were inquired before each PET examination. PET scanning was performed from pelvis to neck with a Siemens ECAT EXACT HR + system. The uptake levels of uterus and ovaries were set as intense, moderate, and mild by comparing to liver uptake.

RESULTSIn 116 patients (131 examinations ) with regular menstruation, the endometrial uptake, usually in inverted cone shape surrounded by relatively low-uptake uterine wall, was observed with two peaks in the early menstrual flow phase and in the mid-cycle respectively; the ovarian uptake was more prominent in the mid-cycle, with the foci of uptake in ovoidal shape and located at the left and/or right side superior-posterior to the bladder. From the early menstrual flow phase to the late secretory phase of the menstrual cycles, the probabilities of mild uptake in both endometrium and ovaries were 7%, 86%, 80%, 58%, 20%, 40%, 64%, and 59%, respectively, indicating that the late menstrual flow phase and the early proliferative phase had the least probability of intense or moderate uptake. No intense uptake was observed in the 17 patients (19 examinations) presenting remarkably irregular menstrual cycle, 112 patients (136 studies) in menopause for 3 months to 39 years, and 2 patients without menstruation yet. Only one patient within 1 year of menopause and a 14-year-old girl expected to start menstruation showed mild to moderate uptake in the endometrium.

CONCLUSIONThe physiological endometrial and ovarian uptakes have specific shapes and positions on 18F-FDG PET images, which correlates well with the menstrual phases.