[18F]FES PET/CT in PAH

This is a feasibility study of serial FES scanning in female patients with Pulmonary Arterial Hypertension (PAH) to determine whether patients have detectable changes in FES SUV following treatment with fulvestrant on the separate therapeutic protocol IRB# 824861 "Estrogen Receptor Antagonist in Patients with Pulmonary Arterial Hypertension (ERA PAH)". Subjects will undergo up to 2 \[18F\]FES PET/CT scans for this protocol. A baseline FES PET/CT will occur on Day 0 (-2 days) of the companion treatment trial prior to initiation of fulvestrant. The second FES PET/CT scan will occur on week 9 (63 ± 7 days) after initiation of fulvestrant. We will compare SUV values after fulvestrant to pre-treatment values.