This is a prospective interventional study of 15 evaluable pediatric patients following a lung transplant that will be studied at the Children's Hospital of Philadelphia in association with the functional and metabolic imaging group of the Perelman School of Medicine from the University of Pennsylvania. Potential subjects will be identified by their pediatric pulmonologist during the follow-up clinic visit for referral to the study. These patients are part of the Lung Transplant Program at CHOP. Before discussing participation in the study, potential subjects will be screened using the protocol inclusion and exclusion criteria. Participation will be discussed between the PI and the referring pediatric pulmonologist. Participation will be discussed with the parents/guardian by the pediatrician and/or radiologist after identification and confirmation of eligibility. Consent will be obtained at the physician's office prior to imaging. A total of approximately 20 patients with ages 8-20 years will be recruited and enrolled to produce up to 15 evaluable subjects.

Hyperpolarized xenon is a novel contrast agent for imaging human lungs using non-invasive Magnetic Resonance Imaging for producing high quality 3D maps of lung structure and function. The xenon gas is inhaled by the subject while inside the MRI scanner and during a short breath-hold the image is acquired. Different MRI techniques can be used to provide regional lung function and structure such as: ventilation, local alveolar oxygen concentration (PAO2) and oxygen uptake rate, apparent diffusion coefficient (ADC), etc. Xenon is soluble in lung tissue and blood with a Chemically Shifted MRI resonant frequency, property which can be quantified through MRI into maps and global parameters related to lung parenchyma and blood exchange.

Early detection of lung transplant complications, such as CLAD, can have life-saving benefit for patients. CLAD is usually diagnosed by spirometry measurements, which are typically not sensitive until late onset of the disease. Longitudinal studies and patient monitoring using HRCT is not desirable due to ionizing radiation and potential long term health hazards. Also, HRCT detects only structural changes of the lung tissue and airways. HP xenon MRI can detect ventilation defects and abnormal gas exchange, which likely can be more sensitive to incipient abnormal lung function.

This study is designed as an open label longitudinal study. Post lung transplant pediatric patients will have two sessions of HP xenon MRI separated by six months. Following parental or legally authorized representative informed consent, the subjects will undergo HP Xenon MR imaging that will be performed in an MRI scanner in at the Hospital of the University of Pennsylvania. Additional conventional proton images of the chest are typically acquired for localization and to assist with interpreting the xenon MR images. These are acquired at the same time and space. After six months, the participant will undergo another hyperpolarized gas MRI as described above to evaluate their progress and evolution.

HP Xenon MRI data will provide high resolution 3D information about the ventilation, oxygen exchange (PAO2), and structural integrity of the alveoli and small airways (ADC). Gas exchange and transport will be assessed from property of xenon to dissolve in lung parenchyma and blood. The signal of the xenon dissolved in the lung tissue and blood compared to the signal of the xenon within the airspaces can be used to extract the septal wall thickness and capillary transit time in the pulmonary vasculature. Data will be used for evaluation of patients for potential lung transplant complications, such as Chronic Lung Allograft Dysfunction (CLAD). This is a longitudinal clinical study. Investigators will study correlations of HP Xenon MRI metrics with CT images and spirometry.