1 Division of Vascular and Interventional Radiology, Stanford University Medical Center, Stanford, CA; Division of Vascular and Interventional Radiology, Stanford University Medical Center, Stanford, CA. Electronic address: wkuo@stanford.edu.
2 Minimally Invasive Techniques Research Group (GITMI), University of Zaragoza, Zaragoza, Spain; Minimally Invasive Techniques Research Group (GITMI), University of Zaragoza, Zaragoza, Spain.