1. From the Center for Systems Biology (M.N., PW., G.T., P.P., B.M., M.J.P., F.K.S., R.W.), Massachusetts General Hospital and Harvard Medical School, Boston; the Center for Molecular Imaging Research (M.N., P.W., P.P., E.A., M.J.P., F.K.S., R.W.), Massachusetts General Hospital and Harvard Medical School, Charlestown; and VisEn Medical Inc (K.G., M.R.), Bedford, Mass.