1. Center for Systems Biology, Massachusetts General Hospital, 185 Cambridge Street, CPZN 5206, Boston, MA 02114, USA.
2. Department of Radiology, Massachusetts General Hospital, Boston, MA 02114, USA.
3. Graduate Program in Immunology, Harvard Medical School, Boston, MA 02115, USA.
4. Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.