Inclusion Criteria:

• 1. Outpatients of either gender, age \> 18
• 2. Willing and able to give informed consent and adhere to visit/protocol (Consent must be given before any study procedures are performed.)
• 3. Subject has no diagnosed pulmonary conditions
• 4. Subject has not smoked in the previous 5 years
• 5. Smoking history, if any, is less than or equal to 5 pack-years
• 6. No history of using other inhaled products more than 1/week for \> 1 year
• Inclusion Criteria for Transfusion and Phlebotomy Patients:
• 1. In-patient or outpatients of either sex, age \> 18
• 2. Willing and able to give informed consent and adhere to visit/protocol
• And one of the following:
• 1. Patients who are scheduled to receive a red cell transfusion for anemia.
• 2. Patients who are scheduled to undergo therapeutic phlebotomy to treat erythrocytosis or polycythemia
• 3. Healthy volunteers undergoing voluntary whole blood donation (healthy volunteer inclusion criteria noted above)
• Inclusion Criteria for Oxygen Administration Patients:
• 1. In-patient or outpatients of either sex, age \> 18
• 2. Willing and able to give informed consent and adhere to visit/protocol
• And one of the following categories (ILD, Dyspnea, CTEPH, or Healthy):
• 1. Interstitial Lung Disease or Dyspnea
• * Physician diagnosis of Interstitial Lung Disease by a pulmonologist using established criteria or physician referral of patient with dyspnea
• OR
• 2. Chronic Thromboembolic Pulmonary Hypertension (CTEPH)
• * Patients with a diagnosis of CTEPH, defined as mean PA pressure \>20 mmHg with a pulmonary vascular resistance \>2 WU and pulmonary capillary wedge pressure ≤15 mmHg at right heart catheterization with evidence of chronic thromboembolic disease on clinical imaging after 3 months of anticoagulation
• * Scheduled for pulmonary thromboendoarterectomy (PTE) surgery and willing to re-turn 3-6 months after for optional follow-up scans
• OR
• 3. Healthy Volunteer (criteria noted above)
• Inclusion Criteria for Acute or Chronic Pulmonary Embolism Patients:
• 1. In-patient or outpatients of either sex, age \> 18
• 2. Willing and able to give informed consent and adhere to visit/protocol
• And one of the following categories (Acute or Chronic)
• 1. Acute Pulmonary Embolism
• * Patients presenting with acute PE 24-48hrs post-admission
• * Willing to return after 3-6 months of anti-coagulation therapy
• OR
• 2. Chronic Thromboembolic Pulmonary Hypertension (CTEPH)
• * Patients with a diagnosis of CTEPH, defined as mean PA pressure \>20 mmHg with a pulmonary vascular resistance \>2 WU and pulmonary capillary wedge pressure ≤15 mmHg at right heart catheterization with evidence of chronic thromboembolic disease on clinical imaging after 3 months of anticoagulation
• * Scheduled for pulmonary thromboendoarterectomy (PTE) surgery and willing to re-turn 3-6 months after for optional follow-up scans
• Exclusion Criteria for All subjects:
• Subjects presenting with any of the following will not be included in the trial:
• 1. MRI is contraindicated based on responses to MRI screening questionnaire
• 2. Subject is pregnant or lactating
• 3. Resting O2 saturation \<90% with maximum supplemental O2 delivered by nasal canula
• 4. Respiratory illness of a bacterial or viral etiology within 30 days of MRI
• 5. Subject has history of any known ventricular cardiac arrhythmia
• 6. Subject has history of cardiac arrest within the last year
• 7. Subject does not fit into 129Xe vest coil used for MRI
• 8. Subject cannot hold his/her breath for 10 seconds
• 9. Subject deemed unlikely to be able to comply with instructions during imaging
• 10. Medical or psychological conditions which, in the opinion of the investigator, might create undue risk to the subject or interfere with the subject's ability to comply with the protocol requirements