Pulmonary arterial hypertension (PAH) is mortal disease affecting the blood vessels of the lung. Despite its morbid prognosis, PAH is often misdiagnosed or ignored, with an average time of 44 months between onset of symptoms to diagnosis and substantial progression of disease severity. Therefore, a pressing need exists to develop non-invasive diagnostic imaging tools, particularly that can detect early disease stages. Efforts have been made to develop such imaging capabilities through platform development of echocardiography, cardiac MRI, chest computed tomography (CT), and positron emission tomography (PET), among others. While some have demonstrated promise, few have shown a precise ability to offer disease quantifications of the diseased lung and vasculature itself, to detect early stages of disease, and to reflect alterations of the lung, vasculature, and right ventricle that reflect the molecular origins of this disease. \[F-18\]FGln has been previously utilized in oncology studies as a non-invasive in vivo imaging biomarker of tumor glutamine flux and metabolism. Our preliminary in vivo pre-clinical rodent studies demonstrated that \[F-18\]FGln demonstrated increased uptake in diseased pulmonary vessels and the right ventricle in a rodent model of PAH. The proposed research study will provide preliminary evidence of the potential to utilize \[F-18\]FGln as a non-invasive imaging biomarker of glutamine flux and metabolism across a range of PAH subjects.