1Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, CA, United States, 2Physics, Ecole Normale Supérieure de Cachan, Cachan, France, 3UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley and University of California, San Francisco, San Francisco, CA, United States, 4Neurology, University of California - San Francisco, San Francisco, CA, United States