1. Department of Surgery, Emory University School of Medicine, Atlanta, GA, USA
2. Research Division, Intuitive Surgical, Norcross, GA, USA
3. Biostatistics Shared Resource, Winship Cancer Institute, Emory University, Atlanta, GA, USA
4. Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA