1. Mechanical Engineering Department, University of Washington, Box 352600, Stevens Way, Seattle, Washington 98195
2. Vascular Imaging Laboratory, Department of Radiology, University of Washington, Box 358050, 850 Republican Street, Seattle, Washington 98109
3. Division of Medical Genetics, Department of Medicine, University of Washington, Box 357720, 1959 NE Pacific Street, Seattle, Washington 98195
4. Mathematical Sciences, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609