1. Department of Electronic Engineering Sogang University Seoul 04107 Korea
2. Department of Health & Medical Equipment Samsung Electronics Co. Ltd. Suwon 16678 Korea
3. Department of Medical Engineering Yonsei University College of Medicine Seoul 03722 Korea
4. Department of Radiology Yonsei University College of Medicine Seoul 03722 Korea
5. Department of Biomedical Engineering Sogang University Seoul 04107 Korea