In vivo imaging of estrogen receptor concentration in the endometrium and myometrium using FES PET--influence of menstrual cycle and endogenous estrogen level.

PURPOSE The goals of this study were to measure estrogen receptor (ER) concentration in the endometrium and myometrium using 16alpha-[(18)F]fluoro-17beta-estradiol (FES) positron emission tomography (PET) and to investigate the relationship between changes in these parameters with the menstrual cycle and endogenous estrogen levels. METHODS Sixteen female healthy volunteers were included in this study. After blood sampling to measure endogenous estrogen level, FES PET image was acquired 60 min postinjection of FES. After whole-body imaging of FES PET, averaged standardized uptake values (SUVs) in the endometrium and myometrium were measured, and the relationship between FES uptake and menstrual cycle or endogenous estrogen level was evaluated. RESULTS Endometrial SUV was significantly higher in the proliferative phase than in the secretory phase (6.03+/-1.05 vs. 3.97+/-1.29, P=.022). In contrast, there was no significant difference in myometrial SUV when the proliferative and secretory phases were compared (P=.23). Further, there was no correlation between SUV and endogenous estrogen level in the proliferative phase. CONCLUSIONS The change of ER concentration relative to menstrual cycle as characterized by FES PET was consistent with those from previous reports that used an immunohistochemical technique. These data suggest that FES PET is a feasible, noninvasive method for characterizing changes in ER concentration.