1. Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
2. Department of Radiology, University of Hacettepe School of Medicine, Ankara 06100, Turkey.
3. Department of Radiology, University of California School of Medicine, Irvine, CA 92697, USA.
4. Department of Radiology, University of Hacettepe, Faculty of Medicine, Ankara 06100, Turkey.