1Department of Biomedical Engineering, Tulane University, New Orleans, LA 70118, U.S.A.
2Bioengineering Program, University of Texas Southwestern Medical Center, Dallas, TX 75235, U.S.A.
3Research Department, Texas Scottish Rite Hospital for Crippled Children, Dallas, TX 75219, U.S.A.
4Department of Biostatistics and Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA 70112, U.S.A.