129Xenon MR Imaging and Spectroscopy Detects Response to Therapy in Pulmonary Hypertension

¹²⁹Xe gas-exchange magnetic resonance imaging/MR spectroscopy (¹²⁹Xe MRI/MRS) is an emerging functional lung imaging technology with the potential to provide precise, spatial, quantitative metrics of pulmonary ventilation, interstitial membrane uptake, transfer to capillary red blood cells (RBCs) and hemodynamics [1–3]. When used in concert, these ¹²⁹Xe MRI/MRS metrics can be used to differentiate between patients with chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), pulmonary arterial hypertension (PAH) and post-capillary pulmonary hypertension (PH) [3]. Incorporation of cardiogenic ¹²⁹Xe-RBC signal oscillations and RBC transfer defects into an initial diagnostic algorithm revealed good sensitivity and specificity in differentiating between pre- and post-capillary PH [4]. However, it is not known whether these ¹²⁹Xe-RBC metrics are sensitive to changes associated with PAH targeted therapies. Here, we addressed this question by performing a descriptive proof-of-concept study using these markers to measure therapy response in PH patients treated with inhaled treprostinil (iTRE).