Hyperpolarized 129Xe MRI for the Assessment of BOS With Late Onset LONIPC

Inclusion Criteria: * For participants who have known LONIPC at enrollment (cross-sectional group): * Patient is 18 - 70 years old * Patient has received an allogenic HSCT * Diagnosed LONIPC For participants who have no known LONIPC, but are at risk by virtue of recently-diagnosed cGVHD: * Patient is 18 - 70 years old * Patient has received an allogenic HSCT in the last 24 months * Patient has a new diagnosis of cGVHD within the last 6 months by criteria of: * Moderate- or severe- cGVHD as per NIH consensus criteria, determined by a treating hematologist or * cGVHD requiring immunosuppression with prednisone at a dose of \> 0.5mg/kg/day, or alternate steroid-sparing agent Exclusion Criteria: * For participants who have known LONIPC at enrollment (cross-sectional group): * Age less than 18 years or greater than 70 years of age * Current smoker (quit in the last 3 months) * Smoking history greater than 20 pack years * Presence of contraindications to pulmonary function testing including myocardial infarction within the last one month, hemoptysis, active communicable disease (e.g. TB), inability to follow commands, thoracic/abdominal/eye surgery within the last 3 months, pneumothorax, uncontrolled hypertension (SBP \> 180, DBP \> 110) or pulmonary embolism, other contraindication as determined by technical staff. * Pregnancy prior to or during study * In the opinion of the investigator, subject is mentally or legally incapacitated, preventing informed consent from being obtained, or cannot read or understand the written material * Patient has an implanted mechanically, electrically or magnetically activated device or any metal in their body which cannot be removed, including but not limited to pacemakers, neurostimulators, biostimulators, implanted insulin pumps, aneurysm clips, bio-prosthesis, artificial limb, metallic fragment or foreign body, shunt, surgical staples (including clips or metallic sutures and/or ear implants) (at the discretion of the MRI Technologist/3T Manager) * In the investigator's opinion, subject suffers from any physical, psychological or other condition(s) that might prevent performance of the MRI, such as severe claustrophobia For participants who have no known LONIPC, but are at risk by virtue of recently-diagnosed cGVHD: * Age less than 18 years or greater than 70 years of age * Known history of late onset non-infectious pulmonary complication (LONIPC) related to HSCT * Current smoker (quit in the last 3 months) * Smoking history greater than 20 pack years * Presence of contraindications to pulmonary function testing including myocardial infarction within the last one month, hemoptysis, active communicable disease (e.g. TB), inability to follow commands, thoracic/abdominal/eye surgery within the last 3 months, pneumothorax, uncontrolled hypertension (SBP \> 180, DBP \> 110) or pulmonary embolism, other contraindication as determined by technical staff. * Pregnancy prior to or during study * In the opinion of the investigator, subject is mentally or legally incapacitated, preventing informed consent from being obtained, or cannot read or understand the written material * Patient has an implanted mechanically, electrically or magnetically activated device or any metal in their body which cannot be removed, including but not limited to pacemakers, neurostimulators, biostimulators, implanted insulin pumps, aneurysm clips, bio-prosthesis, artificial limb, metallic fragment or foreign body, shunt, surgical staples (including clips or metallic sutures and/or ear implants) (at the discretion of the MRI Technologist/3T Manager) * In the investigator's opinion, subject suffers from any physical, psychological or other condition(s) that might prevent performance of the MRI, such as severe claustrophobia