This prospective imaging study investigates the diagnostic ability of Gallium-68 DOTA-TOC (68Ga-DOTA-TOC) positron emission tomography/computed tomography (PET/CT) in the clinical work-up of patients with 1) clinically suspected acute myocarditis (n=30-40) and 2) clinically suspected cardiac sarcoidosis (n=30-40) using clinical diagnostic criteria as well as endomyocardial biopsy as reference. Furthermore, 68Ga-DOTA-TOC PET/CT findings will be compared with results from contrast-enhanced magnetic resonance imaging (MRI) and in case of cardiac sarcoidosis even Fluorine-18 fluorodeoxyglucose (18F-FDG) PET/CT, which are both performed as part of the clinical routine work-up.

Inclusion Criteria:

• Willingness to participate in the study
• Provision of written informed consent
• All patients between the age of 18 and 85 of both genders
• Newly clinically suspected acute myocarditis or newly clinically suspected cardiac sarcoidosis with or without known extra-cardiac sarcoid

Exclusion Criteria:

• Pregnancy or lactation
• Severe obesity (limited by the scanner)
• Other known significant cardiac disease, including previous myocarditis
• Known tumour disease, especially (neuro)endocrine tumours
• Terminal disease(s), advanced psychiatric disease and/or significant dementia
• Recent or current immunosuppressive treatment
• Recent or current somatostatin analogue (octreotide) therapy
• Known relative/absolute contraindications for contrast-enhanced MRI and/or PET/CT imaging
• Known contraindications for endomyocardial biopsy