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Quantitative Analysis of Coronary Arteries Reconstructed by Fusion between Biplane Angiograms and IVUS Images                                         


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Symptomatic coronary artery disease and atherosclerosis are among the leading causes of death in many countries. Frequently, they translate into characteristic local diameter reductions. Coronaries’ motion, foreshortening and overlapping establish severe restrictions on the imaging technologies limiting the automatic assessment of atherosclerotic disease.

The Quantitative Coronary Angiography (QCA) is the standard usually considered for performing this task. Several semi-automatic computer-based systems are available, but the information usually comes from selective single plane angiography and the results are not reliable due to foreshortening or vessel overlaps. When using biplane angiography, the opacified coronary arteries can be geometrically reconstructed in 3-D. This reconstruction delivers information about the vessel topology and geometry, but the cross-sectional shape is restricted to ellipses. Additionally, wall thickness or presence of plaque cannot be estimated. Intravascular ultrasound (IVUS) is a complementary modality which allows to recover the exact cross-sectional shape of the lumen. The IVUS images also allow determination of the vessel wall and plaque. The main limitation of IVUS is that location and spatial orientation of each image frame are unknown.

An approach previously developed at the University of Iowa allows geometrically correct representation of coronary geometry and cross-sectional morphology and is based on fusion of the image data from biplane coronary angiography and intravascular ultrasound . The fusion approach results in a more detailed model for which a highly accurate volume quantification method is required.

Several meaningful measures of quantitative plaque morphometry can be derived from the geometrically correct 3-D representations of the vessel. Quantitative indices are based on the identified lumen/plaque and media/adventitia interfaces in 3-D, called lumen border and wall border, respectively. Three methods for volume measurement were implemented and their measurement accuracy assessed.