Advanced Imaging to Assess the Effect of Immunosuppression on Progressive Fibrosis

Inclusion Criteria: 1. Age 18-80 with a diagnosis of chronic hypersensitivity pneumonitis, connective tissue-associated ILD (due to rheumatoid arthritis, systemic sclerosis, mixed connective tissue disease), or undifferentiated ILD. 2. Starting immunosuppression treatment with mycophenolate mofetil, mycophenolate sodium, and / or prednisone for clinically indicated non-IPF ILD treatment. 3. Pulmonary fibrosis, defined as honeycombing, traction bronchiectasis, or reticular opacities on high-resolution computed tomography (HRCT) performed within 1 year to or at Visit 1. 4. Forced vital capacity (FVC) of \>/= 45% and diffusing capacity of the lungs for carbon monoxide (DLCO) \>/= 25% predicted on PFTs performed at Visit 1. Exclusion criteria: 1. Current or prior exposure to FDA approved anti-fibrotic therapy. 2. Extent of emphysema greater than extent of fibrosis. 3. Pregnancy or plans to become pregnant at baseline or during follow-up. 4. Contraindications to MRI. 5. Contraindications to receiving gadolinium-based contrast agents. 6. Research-related radiation exposure exceeds 50 millisievert (mSv) in the prior year. 7. Estimated glomerular filtration rate (eGFR) \< 30 mL/min (only for individuals with a history of chronic kidney disease). 8. Clinically significant pulmonary hypertension (PH) defined by use of pulmonary vasodilatory therapy. 9. Respiratory infection within the prior 6 weeks. 10. Smoking of any kind within the prior 6 months.