1. From the Department of Nuclear Medicine (M.W., D.W., R.M., Z.Z., H.Z., K.H., L.W., W.F.) and Department of Cardiology, Center for Diagnosis and Management of Pulmonary Vascular Diseases (C.X.), Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, 167 Beilishi Road, Beijing 100037, China.