1. Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
2. Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
3. Department of Biochemistry and Molecular Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
4. CREATIS, CNRS UMR 5220, INSERM U1206, INSA, University Claude Bernard Lyon 1, F69621 Lyon, France