Incidental ovarian 18F-FDG accumulation on PET: correlation with the menstrual cycle

The aim of this study was to determine the nature of incidental ovarian 18F-fluoro-2-deoxyglucose (FDG) accumulation on positron emission tomography (PET) and the correlation with the menstrual cycle and menopause. We identified 19 incidental FDG accumulations in the ovary (FAOs). FDG PET images were compared with other anatomical imaging methods [magnetic resonance imaging (MRI), computed tomography (CT) or ultrasonography (US)]. Pathological findings, FDG PET scan during the next menstrual cycle and follow-up images (PET, CT and MRI) were reviewed. To establish the relation of FAOs to the menstrual cycle, we reviewed whole-body FDG PET acquired from 207 consecutive women and the pre-examination questionnaires, including data regarding the menstrual cycle. All spherical or discoid FAOs were attributed to normally developing ovarian follicles and corpora lutea on the basis of concurrent MRI, US or the follow-up PET scan. Three of the FAOs were proved pathologically to be either normal ovaries or a haemorrhagic corpus luteum. Fifteen FAOs spontaneously disappeared on the short-term follow-up PET scans. Of 207 women, 61 had active menstrual cycles. FAOs were found in 12 out of 61 premenopausal women (20%), appearing between the 10th and 25th days of the menstrual cycle. No FAOs were found in the women who did not have a menstrual cycle. Physiological ovarian FDG accumulation could be found around the time of ovulation and during the early luteal phase of the menstrual cycle in premenopausal woman. Since FAO is dependent on the menstrual cycle, it can be avoided by scheduling PET just after menstruation. (orig.)