Development of FAPI PET as a Non-invasive Biomarker of Pulmonary Fibrogenesis

The goal of this clinical trial is to gain more information about how fibroblast activation protein inhibitor (FAPI) binds to a certain type of cells in fibrotic lung tissue and how this information can be used to better diagnose and track fibrotic lung disease activity. Participants will undergo up to 4 PET/MRI scans using the FAPI radiotracer.

Inclusion Criteria: * Age 18 years or older * Able and willing to provide informed consent * Group A: Clinically evaluated for need for initiation of new treatment (in patients not on current treatment), initiation of change in current treatment, or addition of new treatment (to any current treatment) in the setting of fibrotic hypersensitivity pneumonitis (HSP) or idiopathic pulmonary fibrosis (IPF), per standard of clinical care at UW Health. * Group B: Clinically evaluated and stable without need for initiation of new treatment (in patients not on current treatment), initiation of change in current treatment, nor addition of new treatment (to any current treatment) in the setting of fibrotic hypersensitivity pneu-monitis (HSP) or idiopathic pulmonary fibrosis (IPF), per standard of clinical care at UW Health. * Crossover (Group B to A): Enrolled in Group B and found at next SOC clinical follow up to have need for initiation of new treatment (in patients not on current treatment), initiation of change in current treatment, or addition of new treatment (to any current treatment) in the setting of fibrotic hypersensitivity pneumonitis (HSP) or idiopathic pulmonary fibrosis (IPF), per standard of clinical care at UW Health. * Willing and able to undergo PET/MRI. * Participants requiring intravenous (IV) conscious sedation for imaging are not eligible; participants requiring mild, oral anxiolytics for the clinical MRI will be allowed to participate as long as the following criteria are met: * The subject has their own prescription for the medication * Informed consent is obtained prior to the self-administration of this medication * They come to the research visit with a driver Exclusion Criteria: * Participant is unable or unwilling to provide informed consent * Participant is pregnant * Participant with contraindication(s) to or inability to undergo PET/MRI * Participants with contraindications to GBCA will be asked to undergo research imaging without the use of contrast. Contraindications may be severe kidney disease or previously documented GFR \< 30 ml/min/1.73 m2