FDG-PET as an Imaging Modality to Diagnose and Risk Stratify Subclinical, Imaging Negative Ici-Myocarditis

Inclusion Criteria: * Age ≥18 years at the time of signing informed consent * Any solid or hematologic malignancy undergoing treatment with ICI (either as a single agent or in combination with others) * Ambulatory and able to complete a 48-72 hour high fat and low carbohydrate diet with 18 hours fasting (PET diet), 18F-FDG PET/CT scanning, as well as 13N-ammonia PET-CT myocardial perfusion imaging (part of the routine protocol of the investigation). These two studies will be done as part of the same imaging set. * Willing to return to Mayo Clinic for ongoing follow-up * Left ventricular ejection fraction (LVEF) ≥45% * Cardiac MRI (CMR) without conclusive evidence of inflammation, coronary assessment available (either via cardiac computed tomography angiography, CCTA, or via coronary angiogram) Informed consent obtained before any trial-related activities. Trial-related activities are any procedures that are carried out as part of the trial, including activities to determine suitability for the trial. Exclusion Criteria: * Fulminant myocarditis requiring steroid therapy * CMR with definitive evidence of myocarditis * Clinical presentation consistent with acute coronary syndrome (wall motion abnormalities consistent with a specific coronary distribution, coronary angiogram with a culprit lesion identified, patients requiring revascularization either with percutaneous coronary interventions or coronary artery bypass grafting). * Patients unable to provide informed consent * Patients unable to complete the diet preparation protocol * Pregnancy (all women of child-bearing age and potential will have a negative pregnancy test within 48 hours of the PET/CT at screen and 6-month visit) * Breastfeeding