Fractional flow reserve (FFR) is the reference standard to identify flow-limiting coronary stenosis that requires revascularization. Accurate computation of FFR from coronary intravascular images is based on the precise reconstruction of the side branches. In this paper, a novel approach for segmentation of side branches in intravascular images is presented. The framework consists of an image-to-image translation module and two side branch region segmentation modules. By using the image-to-image translation module, information from intravascular optical coherence tomography (IVOCT) and intravascular ultrasound (IVUS) images is combined to improve the segmentation performance. The framework is trained on a total of 62475 IVOCT and 186110 IVUS images, and evaluated on an independent dataset which contains 9344 IVOCT images with 91 side branches and 39450 IVUS images with 128 side branches. The Dice coefficients of IVOCT and IVUS side branches segmentation are 0.935±0.039 and 0.856±0.038, respectively. The validation results of side branches detection are: Precision = 0.934, Recall = 0.923, F1Score = 0.929 in IVOCT, and 0.925, 0.868, 0.895 in IVUS, accordingly. Ablation studies demonstrate excellent efficiency in incorporating multi-modal information with our proposed image-to-image translation module.
KEYWORDS: 3D modeling, Optical coherence tomography, Angiography, Arteries, 3D image processing, Protactinium, Image fusion, In vivo imaging, Hemodynamics, Image segmentation
The implantation of bioresorbable scaffolds (BRS) alters the local hemodynamic environment. Computational fluid dynamics (CFD) allows evaluation of local flow pattern, shear stress (SS) and Pressure_distal/ Pressure_approximal (Pd/Pa). The accuracy of CFD results relies to a great extent on the reconstruction of the 3D geometrical model. The aim of this study was to develop a new approach for in vivo reconstruction of coronary tree and BRS by fusion of Optical Coherence Tomography (OCT) and X-ray angiography. Ten patients enrolled in the BIFSORB pilot study with BRS implanted in coronary bifurcations were included for analysis. All patients underwent OCT of the target vessel after BRS implantation in the main vessel. Coronary 3D reconstruction was performed creating two geometrical models: one was angiography model and the other was OCT model with the implanted BRS. CFD analysis was performed separately on these two models. The main vessel was divided into portions of 0.15 mm length and 0.15mm arc width for point-perpoint comparison of SS between the two models. Reconstruction of the implanted BRS in naturally bent shape was successful in all cases. SS was compared in the matched 205463 portions of the two models. The divergence of shear stress was higher in the OCT model (mean±SD: 2.27 ± 3.95 Pa, maximum: 142.48 Pa) than that in the angiography model (mean±SD: 2.05 ± 3.12 Pa, maximum: 83.63 Pa). Pd/Pa values were lower in the OCT model than in the angiography model for both main vessels and side branches (mean±SD: 0.979 ± 0.009 versus 0.984 ± 0.011, and 0.951 ± 0.068 versus 0.966 ± 0.051). Reconstruction of BRS in naturally bent shape after implantation is feasible. It allows detailed analysis of local flow pattern, including shear stress and Pd/Pa in vivo.
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