1. Department of Nuclear Medicine; Yonsei University College of Medicine, Gangnam Severance Hospital; Seoul 135-720 Korea
2. Department of Molecular Imaging; Korea Institute of Radiological and Medical Sciences; Seoul 139-706 Korea
3. Department of Pharmacology; Brain Research Institute, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine; Seoul 120-752 Korea
4. College of Pharmacy, Sungkyunkwan University; Suwon Gyeonggi-do 440-746 Korea