1. Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
2. Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Linkou and Chang Gung University, Taoyuan 333, Taiwan.
3. Cardiology Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
4. Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Keelung and Chang Gung University, Keelung 204, Taiwan.