Novel Bifurcation Phantoms for Validation of Quantitative Coronary Angiography Algorithms

Background: Validation is lacking for two- and three-dimensional (2D and 3D) bifurcation quantitative coronary angiography (QCA) algorithms. Methods: Six plexiglas phantoms were designed, each of them mimicking a coronary vessel with three successive bifurcations lesions, wherein at least one vessel segment had a percent diameter stenosis (DS) of >= 60%. The five most frequently occurring Medina classes (1,1,1), (1,1,0), (0,1,0), (0,1,1), and (1,0,0) were used in the design. Diameters of the daughter vessels in every bifurcation were dictated by the scaling law of Finet. Lesions were cosinus-shaped in longitudinal view and circular-shaped in cross-sectional view. At the level of the carina, lesions were becoming eccentric, favoring "plaque" at the outer bifurcation walls. Adjacent bifurcation lesions were kept distant by nontapering, stenosis-free segments of >= 10 mm length. The direction of the side branch relative to the main vessel was based on relevant literature. The phantoms were precision manufactured using computer-aided design and machining techniques. Because of the high drilling accuracy (within 10 mu m), the 3D luminal surface description of the phantom could be used to determine the true lumen dimensions and bifurcation angle (BA) values of the final geometry. Results: Our series of bifurcation phantoms comprised 33 narrowed and 21 stenosis-free vessel segments with a mean true minimal lumen diameter (MLD) value of 0.98 +/- 0.40 mm (range, 0.53-1.96 mm) and 2.29 +/- 0.74 mm (range, 1.40-4.00 mm), respectively. Overall, the mean true values for MLD, reference diameter, and DS were 1.49 +/- 0.85 mm, 2.70 +/- 0.71 mm, and 40.9% +/- 34.2%. The mean true values for the proximal and the distal BA were 123.6 degrees +/- 19.0 degrees and 69.6 degrees +/- 19.9 degrees, respectively. Conclusions: Six plexiglas phantoms containing a total of 18 bifurcations lesions with variable anatomy and Medina class were designed and precision manufactured to facilitate the validation of bifurcation QCA algorithms. (C) 2010 Wiley-Liss, Inc

3D reconstruction techniques of human coronary bifurcations for shear stress computations

Background: Heterogeneity in plaque composition in human coronary artery bifurcations is associated with blood flow induced shear stress. Shear stress is generally determined by combing 3D lumen data and computational fluid dynamics (CFD). We investigated two new procedures to generate 3D lumen reconstructions of coronary artery bifurcations for shear stress computations. Methods: We imaged 10 patients with multislice computer tomography (MSCT) and intravascular ultrasound (IVUS). The 3D reconstruction of the main branch was based on the fusion of MSCT and IVUS. The proximal part of side branch was reconstructed using IVUS data or MSCT data, resulting in two different reconstructions of the bifurcation region. The distal part of the side branch was based on MSCT data alone. The reconstructed lumen was combined with CFD to determine the shear stress. Low and high shear stress regions were defined and shear stress patterns in the bifurcation regions were investigated. Results: The 3D coronary bifurcations were successfully generated with both reconstruction procedures. The geometrical features of the bifurcation region for the two reconstruction procedures did not reveal appreciable differences. The shear stress maps showed a qualitative agreement, and the low and high shear stress regions were similar in size and average shear stress values were identical. The low and high shear stress regions showed an overlap of approximately 75%. Conclusion: Reconstruction of the side branch with MSCT data alone is an adequate technique to study shear stress and wall thickness in the bifurcation region. The reconstruction procedure can be applied to further investigate the effect of shear stress on atherosclerosis in coronary bifurcations. (C) 2013 Elsevier Ltd. All rights reserved