A sample size of 15 patients gives us a 90% power to show a correlation R2 of 0.75. In the ECOM porcine study we have an R2 of 0.77 to 0.84. The 300 patient second section will give us sufficient patient variability (large, small, male, female, young, old, aortic atherosclerosis, aortic regurgitation) to assess the technique across a wide spectrum of patients.