Segmentation and tracking in echocardiographic sequences: active contours guided by optical flow estimates.

This paper presents a method for segmentation and tracking of cardiac structures in ultrasound image sequences. The developed algorithm is based on the active contour framework. This approach requires initial placement of the contour close to the desired position in the image, usually an object outline.

Real-time continuous measurement of right ventricular volume using a conductance catheter.

The authors propose using a multi-electrode conductance catheter to measure continuous right ventricular volume. True ventricular volume measurements are affected by four main sources of error. 1) field non-uniformity, 2) catheter curvature, 3) blood conductivity changes, and 4) leakage of current through surrounding tissues.

An optimal mounting frame to reduce flexural stresses of bioprosthetic heart valves.

Recent studies suggest that sharp bending of valve leaflets during the opening phase may be the reason for much of the mechanical failure of bovine pericardial bioprostheses. Sharp bending of the valve leaflets is promoted by the rigid, non expanding stents upon which the leaflets are mounted. We hypothesized that sharp bends and the associated flexural stresses could be significantly reduced by incorporating a stent that expands with the recipient aorta during systolic valve opening.

Numerical simulation of leaflet flexure in bioprosthetic valves mounted on rigid and expansile stents.

Recent studies suggest that flexural stresses induced during the opening phase may be responsible for much of the mechanical failures of bioprosthetic heart valves. Sharp leaflet bending is promoted by the mounting of valves on rigid stents that do not mimic the systolic expansion of the natural aortic root. We, therefore, hypothesized that flexural stresses could be significantly reduced by incorporating a flexible or expansile supporting stent into the valve design.

Micromechanics and mathematical modeling: an inside look at bioprosthetic valve function.

A major contributing factor in the degeneration of glutaraldehyde-treated porcine xenograft bioprostheses is tearing of the valve cusps near their commissural attachment to the supporting stent. We have been examining aortic valves at the micromechanical level, and have developed several sensitive techniques to evaluate the biomechanical changes produced by the glutaraldehyde fixation process. Additionally, we have developed a mathematical modeling technique that stimulates valve function during the entire cardiac cycle.