The effect of image distortion on 3-D reconstruction of coronary bypass grafts from angiographic views.

Three-dimensional (3-D) reconstructions of coronary bypass grafts performed from X-ray angiographic images may become increasingly important for the investigation of damaging mechanical stresses imposed to these vessels by the cyclic movement of the heart. Contrary to what we had experienced with coronary arteries, appreciable reconstruction artifacts frequently occur with grafts. In order to verify the hypothesis that those are caused by distortions present in the angiographic images (acquired with image intensifiers), we have implemented a grid correction technique in our 3-D reconstruction method and studied its efficiency with phantom experiments.

In-vivo measurements of wall shear stress in human coronary arteries.

Background: Wall shear stress (WSS) is closely associated with arteriosclerosis. WSS values for various vessels and species are available, but fully in-vivo measurements in human coronary arteries have not yet been reported.

Objective: To measure WSS in undiseased coronary arteries of adult patients at rest.

Accuracy of coronary flow measurements performed by means of Doppler wires.

To estimate in patients the accuracy of coronary flow measurements performed by means of 0.014" Doppler wires, the time-averaged maximal blood velocity (APV) was recorded in the 3 branches of 36 angiographically normal coronary artery bifurcations selected in 21 patients undergoing cardiac catheterization for various diseases. Contrast medium injections filmed under two incidences allowed identification of the 3 sample volume locations and computing of the 3 corresponding vessel cross-sectional areas (CSA) at subsequent data analysis.

Is the indicator dilution theory really the adequate base of many blood flow measurement techniques?

The indicator dilution theory is the underlying model of many blood flow measurement techniques used daily in hospitals, for instance in cardiac catheterization laboratories. The basic version of this theory applies to a "stationary" flow system with one inlet and one outlet, into which a small amount M of indicator is injected "suddenly" at time t = 0 at the inlet. The quintessence of the theory consists in three equations, which themselves result from some apparently simple assumptions about the considered flow systems.

Towards a gold standard for quantitative coronary arteriography.

Densitometric quantification of coronary artery stenoses in angiographic images can be problematic for two reasons: (i) the x-rays are inadequately oriented with respect to the vessel segments of interest at image acquisition; (ii) non-linear effects due for instance to beam hardening, scattered radiation and veiling glare may reduce the accuracy. As a consequence, appreciable discrepancies between degrees of stenosis measured in two different projections can occur. To overcome these limitations, we have designed and tested a combined correction that compensates (at subsequent analysis) for the error contributions due to the cited sources.