This is a pilot study to determine the utility of Novel Functional Lung Imaging and Ventilation (4DxV) Analysis software in measurement of lung ventilation abnormalities and diagnosis of chronic lung allograft dysfunction (CLAD) after lung transplantation.

This is a pilot study to determine the feasibility and utility of Novel Functional Lung Imaging and Ventilation (4DxV) Analysis software in measurement of lung ventilation abnormalities and diagnosis of CLAD after lung transplantation. 4DxV is a technology developed by 4Dx (4Dx Limited, Melbourne, Australia and Los Angeles, CA) and is a novel computational approach to the data obtained from standard fluoroscopic imaging that measures tissue motion of the lung at all locations and in all phases of breath. These motion measurements are used to calculate 4-dimensional ventilation (4DxV) of lung tissue to provide variety of outputs. The investigators will establish the sensitivity, specificity, and accuracy of this technology in diagnosis of CLAD compared to CT scan and pulmonary function results in patients with a known diagnosis of CLAD based on established diagnostic criteria.

The investigators will test the following hypotheses:

1. 4DxV scans will be able to detect quantitative ventilation abnormalities in patients with established CLAD and the severity of the abnormalities will correlate with severity of PFT decline
2. 4DxV will be able to diagnose patients with CLAD of the bronchiolitis obliterans syndrome (BOS) phenotype grades 0 (CLAD free) vs grades 1-3

Inclusion Criteria:

1. Greater than or equal to 18 years of age at the time of written informed consent

2. Recipient of a first bilateral lung transplantation performed at Duke University at least one year prior to written informed consent

3. Computed tomography (CT) scan of the chest performed at Duke as standard of care after transplantation but within 1 year prior to written informed consent 4a. CLAD grades 1, 2,or 3 (per ISHLT 2014 criteria [Meyer et al 2014]) prior to or at the time of screening

   • Grade 1 is defined as a fractional decrease in FEV1 to 66-80% of post-transplant baseline FEV1
   • Grade 2 is defined as a fractional decrease in FEV1 to 51%-65% of post-transplant baseline FEV1
   • Grade 3 is defined as a fractional decrease in FEV1 to <= 50% of post-transplant baseline FEV14b. CLAD free status (defined as most recent FEV1 at the time of screening >90% of post-transplant baseline FEV1)

Exclusion Criteria:

1. Recipients of a single lung transplant
2. Recipients of a redo-lung transplant
3. Recipients of bone marrow or stem cell transplant
4. Recipients of a multi-organ transplant
5. Patients with hospital admissions(excluding admissions for planned treatment of the CLAD and/or rejection)within one month of screening.
6. Patients who are unable to lie flat on the fluoroscopy table
7. Pregnant women (by subject's verbal report). Lung transplant recipients are routinely counseled to avoid pregnancy due to the teratogenic effects of necessary immunosuppressant medications. Pregnancy after lung transplantation is therefore extremely rare. As this is a minimal risk study which does not involve an experimental therapy, invasive devices, or increased risk procedures, pregnancy testing is deemed unnecessary for this population for this study.