TOWARDS A GOLD STANDARD FOR QUANTITATIVE CORONARY ARTERIOGRAPHY

Densitometric quantification of coronary artery stenoses in angiograph ic images can be problematic for two reasons: (i) the x-rays are inade quately oriented with respect to the vessel segments of interest at im age acquisition; (ii) non-linear effects due for instance to beam hard ening, scattered radiation and veiling glare may reduce the accuracy. As a consequence, appreciable discrepancies between degrees of stenosi s measured in two different projections can occur. To overcome these l imitations, we have designed and tested a combined correction that com pensates (at subsequent analysis) for the error contributions due to t he cited sources. It implies 3D reconstruction of the vessel segments of interest and consequently requires an appropriate biplane coronary angiogram. In experiments performed with a dedicated phantom, applicat ion of the correction improved the correlation between measured and tr ue area reduction percentages (without correction: y = 1.04x - 4%, r = 0.97, SEE = 6%, n = 35; with correction: y = 1.02x - 0%, r = 0.99, SE E = 3%, n = 35). Applied to ten area stenoses measured biplane in pati ents and exhibiting strong interplane discrepancies, the correction ha d a comparable effect (without correction: y = 0.83x - 11%, r = 0.86, SEE = 9%, n = IO; with correction: y = 0.83x + 2%, r = 0.98, SEE = 4%, n = 10). The new densitometric method could possibly be used as a gol d standard in the objective evaluation of geometric methods in patient s.