Findings of physiological FDG uptake in the surgically transpositioned ovary

Objectives The physiologic FDG uptake of the ovary is one of the well-known normal variants, frequently found in the pelvis. Ovary transposition is performed to save ovary function in premenopausal women who are scheduled to undergo pelvic radiation therapy. The purpose of this study was to evaluate the FDG PET-CT findings of transpositioned ovaries.

Methods Seventy FDG PET-CT studies from 30 patients were included in this retrospective study from Jan 2007 to Dec 2014. All patients underwent ovarian transposition to preserve ovarian function, before radiation treatment. Primary cancers were as follows: uterine cervix cancer: 22, rectal cancer: 5, endometrial cancer: 1, and etc: 2. After confirmation of all patients’ surgical history, FDG PET finding were analyzed visually. For quantitative analysis, standardized uptake value (SUV) of the transpositioned ovaries was measured.

Results In all the patients, transpositioned ovaries were identified by FDG PET-CT alone or by enhanced CT. 59 of cases were detected by FDG PET visually. The SUVmax of the transpositioned ovary ranged from 0.79 to 9.48. The mean SUVmax range of the left transpositioned ovary was 1.74 (0.79 ~ 6.48) and that of the right was 1.47 (1.01~ 9.48). In some cases, focal FDG uptakes in the transpositioned ovary mimicked seeding metastasis. It was especially frequent in the right transpositioned ovary at right paracolic gutter, which is the seeding metastasis-prone position. In addition to surgical record, contrast enhanced CT finding and surgical clip were important clues to detect transpositioned ovary. In 6 patients with follow-up PET were performed, its SUVmax showed variable changes during the period.

Conclusions We could not assess menstrual cycles including last normal menstrual period, because all patients underwent hysterectomy. Similar to normal ovary, the transpositioned ovaries showed a broad range of SUVmax. We demonstrated that the FDG uptakes in transpositioned ovary were variable, and it should be differentiated from seeding metastasis.