Endometriosis is a benign chronic disease responsible for infertility and pelvic pain. One of the main problem of endometriosis is the significant delay of diagnosis.This delay has significant consequences for patients. Currently the definitive diagnosis of endometriosis and the evaluation of its lesional extension require performing laparoscopy and a histological analysis of biopsy and pathologic areas. Lesions of endometriosis whose development and growth are estrogen-dependent, express estrogen receptor (ER). [18F]FES (16α-[18F]Fluoro-17β-estradiol) is an analog of estrogen, used in positron emission tomography (PET), and a specific tracer of ER. We propose to evaluate the performance of this functional imaging as a diagnostic tool for endometriosis.