A Clinical Trial to Investigate 18F-AzaFol in the Diagnosis of Large Vessel Vasculitis

Inclusion Criteria: * Individuals ≥ 50 years with clinical suspicion of GCA * Women of childbearing potential must not have a positive serum pregnancy test at the Screening Visit * Subjects must be able to understand and adhere to all protocol requirements and must voluntarily sign and date an informed consent, approved by an independent ethics committee (IEC)/institutional review board (IRB), prior to the initiation of any screening or study-specific procedures. * Are willing and able to comply with procedures required in this protocol. Exclusion Criteria: 1. Folate deficiency 2. Female subjects who are pregnant, breastfeeding, or considering becoming pregnant during the study or within 30 days after the last dose of study drug 3. Concomitant treatment with medications that lead to a significant impairment of folic acid levels (methotrexate, pemetrexed, raltitrexed) 4. Concomitant glucose-containing infusion or parental nutrition within 6 hours prior to 2-\[18F\]FDG tracer application 5. Glucose level \> 10 mmol/l at the timepoint of 2-\[18F\]FDG PET/CT 6. Unable to remain in the PET/CT for the duration of the examination 7. Unable to lie still for the duration of the examination (45 min) 8. Unable not to eat or drink (except water) for 6 hours prior to 2-\[18F\]FDG tracer application 9. Prior PET-imaging within 60 days before baseline 10. Intake of vitamin supplements containing \> 1mg/day folic acid within 48 h prior to the PET/CT with AzaFol 11. Known hypersensitivity or allergy to folic acid 12. Enrolment of the investigator, his/her family members, employees and other dependent persons 13. Participation in another study with investigational drug within the 7 days preceding and during the present study.