Xenon MRI Pulm Hypertension

This study uses a special type of MRI scan with inhaled xenon gas to better understand how the lungs work in patients with pulmonary hypertension (high blood pressure in the lungs). It aims to track how this condition changes over time and how patients respond to treatment. **You may be eligible if...** - You are 18–75 years old - You have been diagnosed with pulmonary hypertension confirmed by a heart catheterization test - Either: you are waiting for a lung transplant (Cohort 1), OR you have newly diagnosed Group 1 pulmonary arterial hypertension (Cohort 2) - You are willing and able to sign consent and attend required visits - If you are a woman who could become pregnant, you must have a negative pregnancy test before MRI **You may NOT be eligible if...** - You have severe heart disease (poor heart function or significant valve disease) - You have active cancer, sickle cell anemia, or severe liver disease (Child-Pugh C) - You are pregnant - You cannot have an MRI (metal implants, severe claustrophobia, unable to lie flat) - You have sarcoidosis (Cohort 2 only) Talk to your doctor to see if this trial is right for you.