Automatic quantification of intravascular optical coherence tomography

As mentioned above, IVOCT, as a novel imaging modality, has played an active role in a wide range of CAD applications, including research and clinical routine. Due to its unparalleled high resolution and the ability to delineate complex vascular structures, IVOCT technology makes many precise measurement and novel applications possible. However, currently, a lot of analyses in IVOCT images are still relying on the manual work which decreases their value. The goal of this thesis is to develop robust and accurate (semi)automated methods that can detect and segment the interesting components in IVOCT pullback runs, such as implanted stent struts and side branches in 3D for accurate measurement, so that the results could contribute to medical research as well as for clinical decision-making. My thesis presents four different automated algorithms to detect metallic stent struts, bioresorbable vascular scaffold struts, side branches and all the common components in IVOCT images. It also presented a semi-automated method to assess the stent support to vessel wall and the stent-jailed side branch access through stent cells in 3-dimentional spaceChina Scholarship Council (CSC)UBL - phd migration 201

A patient-specific study investigating the relation between coronary hemodynamics and neo-intimal thickening after bifurcation stenting with a polymeric bioresorbable scaffold

We present an application of a validated reconstruction methodology for the comparison between patient-specific hemodynamics and neo-intimal thickening at nine months from the intervention. (1) Background: Coronary bifurcation stenting alters the vessel geometry, influencing the local hemodynamics. The evaluation of wall shear stress (WSS) relies on the application of computational fluid dynamics to model its distribution along the coronary tree. The endothelium actively responds to WSS, which triggers eventual cell proliferation to cover the stent struts. (2) Methods: Baseline optical coherence tomography and angiographic data were combined to reconstruct a patient-specific coronary bifurcation with an implanted bioresorbable scaffold and to simulate the hemodynamics. Results were linked with the neo-intimal thickening after nine months from the intervention. (3) Results: Blood velocity patterns were disrupted at the bifurcation due to the presence of the stent. It was observed that 55.6% of the scaffolded lumen surface was exposed to values of time-averaged WSS lower than 0.4 Pa. Follow-up images showed a luminal narrowing of 19% in the main branch. There was also a complete coverage in 99% of struts. (4) Conclusions: This approach provided valuable complementary information that might improve the clinical outcomes in this subset of coronary diseases

Intravascular Ultrasound

Intravascular ultrasound (IVUS) is a cardiovascular imaging technology using a specially designed catheter with a miniaturized ultrasound probe for the assessment of vascular anatomy with detailed visualization of arterial layers. Over the past two decades, this technology has developed into an indispensable tool for research and clinical practice in cardiovascular medicine, offering the opportunity to gather diagnostic information about the process of atherosclerosis in vivo, and to directly observe the effects of various interventions on the plaque and arterial wall. This book aims to give a comprehensive overview of this rapidly evolving technique from basic principles and instrumentation to research and clinical applications with future perspectives

Intravascular OCT tissue type imaging by automated optical attenuation analysis

We developed attenuation imaging in OCT for atherosclerotic tissue characterization and validated the method ex and in-vivo. We introduced an en-face map of attenuation in the whole artery for plaque visualization. We quantified the attenuation derived from OCT and derived an index for the plaques. A single centre clinical study (OC3T study) was conducted to validate the index to identify thin cap fibroatheromas. We also demonstrated the utility of the attenuation maps and the index in clinical studies as corresponding well with a visual assessment of LCP in the OCT data by expert readers

Optical coherence tomography for the assessment of coronary atherosclerosis and vessel response after stent implantation

Optical Coherence Tomography (OCT) is a light-based imaging modality that can provide in vivo high-resolution images of the coronary artery with a level of resolution (axial 10-20 µm) ten times higher than intravascular ultrasound. The technique, uses low-coherent near infrarred light to create high-resolution cross sectional images of the vessel. The technology refinement achieved in the last years has made this imaging modality less procedurally demanding opening its possibilities for clinical use. The present thesis provides im

Bioresorbable coronary stents : non-invasive quantitative assessment of edge and intrastent plaque – a 256-slice computed tomography longitudinal study

Les bioresorbable stents (BRS), en français intitulés tuteurs coronariens biorésorbables, sont constitués d’un polymère biorésorbable, plutôt que de métal, et ne créent pas d’artéfacts métalliques significatifs en tomodensitométrie (TDM). Cela permet une meilleure évaluation de la plaque coronarienne sous ces tuteurs en TDM qu’avec les anciens tuteurs qui sont en métal. OBJECTIF: Évaluer l’évolution de la composition de la plaque, sa fraction lipidique (FL)— marqueur de vulnérabilité de la plaque, dans les 3 zones pré-tuteur (bord proximal), intra-tuteur et post-tuteur (bord distal), et le volume de la plaque entre 1 et 12 mois post-implantation de BRS. MÉTHODOLOGIE: Il s’agit d’une étude observationnelle longitudinale réalisée chez 27 patients consécutifs (âge moyen 59,7 +/- 8,6 ans) et recrutés prospectivement pour une imagerie par TDM 256-coupes à 1 et 12 mois post-implantation de BRS (35 tuteurs total). Les objectifs primaires sont: volume de plaque totale et de FL (mm3) comparés entre 1 et 12 mois. Afin de tenir compte de la corrélation intra-patient, des analyses de variance des modèles linéaires mixtes avec ou sans spline sont utilisés avec deux facteurs répétés temps et zone/bloc (1 bloc= 5 mm en axe longitudinal). La valeur % FL= volume absolu du FL/ volume total de la plaque. RÉSULTATS: Notre analyse par bloc ou par spline n’a pas démontré une différence significative dans les volumes de plaque ou des FL dans les zones pre- intra- and post-tuteur entre 1 et 12 mois. CONCLUSION: Notre étude a réussi à démontrer la faisabilité d’une analyse non-invasive quantitative répétée de la plaque coronarienne et de la lumière intra-tuteur avec l’utilisation de TDM 256 coupes. Cette étude pilote n’a pas démontré de différence significative dans les volumes des plaques et atténuation entre 1- et 12- mois de follow-up post-implantation de BRS. Notre méthode pourrait être appliquée à l’évaluation des différents structures ou profils pharmacologiques de ces tuteurs.Coronary bioresorbable stents (BRS) are made of a bioresorbable polymer rather than metal. Unlike metallic stents, BRS do not produce significant artifacts in computed tomography (CT) and are radiolucent in CT, making it possible to evaluate coronary plaque beneath an implanted stent. PURPOSE: The purpose of our study was to evaluate the volumes of plaque and low attenuation plaque components (LAP —a marker of plaque vulnerability) of pre-, intra- and post-stent plaque location between 1 and 12 months post-implantation. METHODS: In our prospective longitudinal study, we recruited 27 consecutive patients (mean age 59.7 +/- 8.6 years) with bioresorbable stents (n=35) for a 256-slice ECG-synchronized CT evaluation at 1 month and at 12 months post stent implantation. Total plaque volume (mm3) as well as absolute and relative (%) LAP volume per block in the pre-, intra- and post-stent zones were analyzed; comparison of 1 and 12 months post BRS implantation. Changes in these variables were assessed using mixed effects models with and without spline, which also accounted for correlation between repeated measurements with factors such as time and zone/block (1 block = 5 mm in longitudinal axis). The value % LAP= LAP absolute volume/ total plaque volume. RESULTS: Our block or spline model analysis showed no significant difference in plaque or LAP volumes in pre-, intra- and post-stent zones measured at 1 month and at 12 months. CONCLUSION: Our study demonstrates the feasibility of repeated non-invasive quantitative analysis of intrastent coronary plaque and in-stent lumen using a 256-channel CT scan. This pilot study did not show significant differences in plaque volume and attenuation between 1- and 12-month follow-up from stent implantation. The method we used could be applied to the evaluation of different stent structures or different pharmacological profiles of bioresorbable stents