Prospective Trial of [18F]AlF-FAPI-74 for PET Imaging of Fibroblast Activation Protein in Patients With Endometriosis

Inclusion Criteria: * Voluntary written informed consent of the participant has been obtained prior to any screening procedures. * At least 18 years of age at the time of signing the Informed Consent Form (ICF). * At least one of the following to be eligible for the DE cohort: (i) Clinical suspicion of DE, defined as the presence of deep nodule(s) during vaginal examination determined by a clinician who is an expert in endometriosis. (ii) Diagnostic suspicion of DE, defined as an ultrasound and/or MRI that shows lesions suspicious for DE. * At least one of the following to be eligible for the SPE cohort: (i) Clinical suspicion of SPE, defined as clinical symptoms suspicious of SPE determined by a clinician who is an expert in endometriosis. These clinical symptoms include dysmenorrhea, deep dyspareunia, dysuria, dyschezia, painful rectal bleeding or haematuria, shoulder tip pain, catamenial pneumothorax, cyclical cough/haemoptysis/chest pain, cyclical scar swelling and pain, fatigue, and infertility. (ii) Diagnostic suspicion of SPE, defined as an ultrasound and/or MRI that shows lesions suspicious for SPE. * Planned laparoscopy for suspected endometriosis. Exclusion Criteria: * For SPE cohort: (i) Ultrasound and/or MRI with lesions suspicious of ovarian endometriosis and/or DE. (ii) Clinical symptoms suspicious of ovarian endometriosis and/or DE, determined by a clinician who is an expert in endometriosis. * Prior abdominal surgery less than one year ago. * Female who is pregnant, breastfeeding or is of childbearing potential and not using an adequate, highly effective contraceptive or no usage of contraception when sexually active are not accepted. * Participant is mentally or legally incapacitated, does not understand the study design or is not willing or capable to undergo all study-specific procedures. * Any disorder or condition, which in the Investigator's opinion might jeopardise the participant's safety or compliance with the protocol, or may influence the result of the study. * Any prior or concomitant treatment(s) that might jeopardise the participant's safety or that would compromise the integrity of the Trial. * Participation in an interventional Trial with an investigational medicinal product (IMP) or device when the trial designs are not considered compatible by the study team. * Participation in a clinical scientific study in the last 12 months with a radiation exposure caused by the experimental procedures greater than 1 mSv. * Participant has a known hypersensitivity to \[18F\]AlF-FAPI-74 or the used excipients.