[1] MIT, David H Koch Inst Integrat Canc Res, Cambridge, MA 02139 USA
[2] MIT, Dept Mech Engn, Cambridge, MA 02139 USA
[3] Harvard Med Sch, Div Gastroenterol Hepatol & Endoscopy, Brigham & Womens Hosp, Boston, MA 02115 USA
[4] Harvard Med Sch, Dept Neurosurg, Brigham & Womens Hosp, Boston, MA 02115 USA
[5] Harvard Med Sch, Massachusetts Gen Hosp, Dept Neurosurg, Boston, MA 02115 USA