The purpose of this study is to determine if measurements of active collagen deposition using [68Ga]CBP8 positron emission tomography (PET) and tissue injury using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can predict an individual patient's pace of disease progression in non-idiopathic pulmonary fibrosis interstitial lung disease (non-IPF ILD) and identify which individuals will develop progressive pulmonary fibrosis.

60 participants with non-idiopathic pulmonary fibrosis interstitial lung disease (non-IPF ILD) on stable dose immunosuppression treatment will be enrolled. Participants will undergo combined [68Ga]CBP8 positron emission tomography (PET) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) at baseline. The investigators will compare the ability of PET and MRI measurements performed over the whole lung and within regions of interest to identify participants who subsequently develop progressive pulmonary fibrosis as determined by changes in pulmonary function testing, quantitative fibrosis on high-resolution computed tomography, and respiratory symptoms over 24 months. The investigators will also test whether combining the PET and MRI measurements results in more accurate prediction of progression than either modality alone.

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. On stable dose immunosuppression treatment (with prednisone, mycophenolate mofetil, mycophenolate sodium, and/or rituximab) for at least 3 months.
3. Pulmonary fibrosis, defined as honeycombing, traction bronchiectasis, or reticular opacities on HRCT performed within 1 year to or at Visit 1.
4. FVC of >/= 45% and 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 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 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.