Fasting FDG-PET will be performed in patients with sarcoidosis and age-matched DCM patients. Among them, systemic sarcoidosis will be diagnosed clinically and/or histologically, and referred for cardiac sarcoidosis. Patients with sarcoidosis will reveal cardiac involvement based on guidelines established in 2006 by the Japanese Ministry of Health and Welfare. Healthy control subjects will undergo FDG-PET.