Repurposing Tilmanocept for Cardiac Sarcoidosis

Inclusion Criteria: Cohort 1: 1. The participant has provided written informed consent with HIPAA (Health Information Portability and Accountability Act) or equivalent authorization before the initiation of any study-related procedures. 2. Women of reproductive potential must have a negative urine pregnancy test at the time of the study. 3. The participant is at least 18 years of age. 4. The participant has a histological diagnosis sarcoidosis and meets 2014 HRS, 2014 WASOG, or 2016 JCS criteria for cardiac sarcoidosis. 5. The participant has had a clinically indicated cardiac PET-CT showing cardiac activity in the past 14 days. 6. The participant has had a prior cardiac MRI with delayed enhancement in pattern consistent with cardiac sarcoidosis as defined in the AHA Scientific Statement on the Diagnosis and Management of Cardiac Sarcoidosis (2024). Cohort 2: 1. The participant has provided written informed consent with HIPAA (Health Information Portability and Accountability Act) or equivalent authorization before the initiation of any study-related procedures. 2. Women of reproductive potential must have a negative urine pregnancy test at the time of the study. 3. The participant is at least 18 years of age. 4. Cardiac sarcoidosis has been clinically excluded. 5. The participant has an arrhythmogenic, non-ischemic cardiomyopathy defined as the presence of a cardiomyopathy with a history of recurrent (more than 1 episode) ventricular tachycardia, atrial arrhythmias, high grade AV block not due to ischemic heart disease Exclusion Criteria: 1. The participant is pregnant or lactating. 2. The participant size or weight is not compatible with imaging per the investigator. 3. The participant has renal insufficiency as demonstrated by a glomerular filtration rate of \< 30 mL/min. 4. The participant has hepatic insufficiency as demonstrated by ALT (alanine aminotransferase \[SGPT\]) or AST (aspartate aminotransferase \[SGOT\]) greater than 3 times the upper limit of normal. 5. The participant has any severe, acute, or chronic medical conditions and/or psychiatric conditions and/or laboratory abnormalities that would impart, in the judgment of the investigator, excess risk associated with study participation or study drug administration that would deem the subject inappropriate for study participation. 6. The participant has a known allergy to or has had an adverse reaction to dextran exposure. 7. The participant has received an investigational product within 30 days prior to the Tc 99m tilmanocept administration (Day 0). 8. The participant has received any radiopharmaceutical within 7 days or 10 half-lives prior to the administration of Tc 99m tilmanocept (Day 0).