RecruitingPhase 2Drug trialPulmonary Hypertension SOLARThe main goal of this study is to develop a noninvasive signature for pulmonary vascular remodeling in Group 3 PH patients, using hyperpolarized 129Xe magnetic resonance imaging (129Xe MRI). Such a signature may identify Group 3 PH responders to PAH-specific therapies. PAH's unique 129Xe MRI signature has been shown in previous studies. Past studies have lacked a pathologic "ground truth" correlate of these signatures, which could be provided by comparing them with the pathology of lung explant tissue from patients who have undergone a lung transplant. This signature could be validated in a cohort of patients with Group 3 PH in future studies.