Which phase of menstrual cycle shows the physiological 18F-FDG uptake of ovary? Comparison between FDG-PET and pelvic MRI on the same day

1286 Objectives: Physiological 18F-fluorodeoxyglucose (FDG) uptake of the ovary is sometimes observed in FDG positron emission tomography (PET) of premenopausal female. The purpose of this study is to estimate the correlation between ovarian FDG uptake and ovarian activity visualized on magnetic resonance imaging (MRI). Methods: One hundred and fifty-two FDG-PET scans of healthy premenopausal females, whose menstrual cycle were identified, were obtained on whole body PET scanner (Discovery LS, GE Medical Systems, Milwaukee, WI, USA). And pelvic MRI scans were examined on the same day, using 1.5T MRI scanner (Impact Vision, Siemens AG, Erlangen, Germany). About the population detected ovarian FDG uptake, the FDG-PET findings were compared with the MRI findings of ovaries. Results: Thirty-six ovarian FDG uptakes (32 unilateral and 2 bilateral cases) were found in 152 females (22.4%). Twenty-three of 36 (including 2 bilateral cases) were in follicular phase and 17 dominant follicles were identified. Remaining 13 of 36 were in luteal phase and 11 corpus luteums were identified. Distribution of FDG uptake compared with ovarian structures is indicated in figure. Ovarian FDG uptakes were correlated with 10 of 17 dominant follicles (58.8%) and 9 of 11 corpus luteums (81.8%). Nine of 28 ovarian structures (32.1%) were not correlated with ovarian FDG uptakes. Conclusions: There was a tendency that physiological FDG uptakes of ovary were observed more in late follicular phase. At a rate of 32.1%, there was discrepancy between the existence of ovarian FDG uptake and the MRI findings indicating activated ovary. As an explanation of this, involvement of “menstruation without ovulation” was proposed. It seems not easy to decide pathological or physiological about the incidental ovarian FDG uptake.