1Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC, United States, 2Medical Physics Graduate Program, Duke University, Durham, NC, United States, 3Department of Radiology, Duke University Medical Center, Durham, NC, United Kingdom, 4Department of Biomedical Engineering, Duke University, Durham, NC, United States, 5Department of Radiology, Duke University Medical Center, Durham, NC, United States