Purpose: This study was designed to characterize the physiological endometrial and ovarian F-18 FDG uptake through analysis of clinical patients with serial PET follow ups (group 1) or who underwent delayed imaging (group 2).
Methods: Group 1 had 24 patients (14 premenopausal and 10 postmenopausal). Each patient underwent 2 to 4 serial FDG PET studies and summed to 57 studies. Group 2 included 15 premenopausal patients with delayed imaging 3 hours after injection. Ten of them showed endometrial uptake, and 8 showed intense uptake in 10 ovaries. Visual and semiquantitative methods were applied for analysis.
Results: By analysis of serial PET studies, endometrial and ovarian uptake showed some specific characteristics. Surrounded by a relatively low-uptake uterine wall, the inverted cone-shaped endometrium showed 2 peaks of uptake, one in early menstruation and the other in midcycle. The ovarian uptake was more prominent in the midcycle, and the foci of uptake had an ovoid shape and located at the left and/or right side superior-posterior to the bladder. For the postmenopausal and amenorrhea women (35 studies), only one study in a woman within 1 year of menopause showed mild endometrial and ovarian uptake. Compared with the imaging 1 hour after injection, the standardized uptake value increased in 2 of 10 endometria and 4 of 10 ovaries in the delayed imaging.
Conclusion: Physiological endometrial and ovarian uptake can be identified on PET alone by their specific shape and position as well as their relation to the menstrual state, whereas delayed imaging was of little value for differentiation in this preliminary study.