Validating Intravascular Imaging with Serial Optical Coherence Tomography and Confocal Fluorescence Microscopy.

Pier-Luc Tardif,Jean-Claude Tardif,Teodora Mihalache-Avram,Philippe L’Allier,Abedelnasser Abulrob,Mélanie Mecteau,Joël Lefebvre,Marie-Jeanne Bertrand,Maxime Abran,Nolwenn Merlet,Éric Rhéaume,Pascale Geoffroy,Feng Ni,Barbara Stähli,Alexandre Castonguay,Frédéric Lesage,David Busseuil

doi:10.3390/ijms17122110

Abstract

Atherosclerotic cardiovascular diseases are characterized by the formation of a plaque in the arterial wall. Intravascular ultrasound (IVUS) provides high-resolution images allowing delineation of atherosclerotic plaques. When combined with near infrared fluorescence (NIRF), the plaque can also be studied at a molecular level with a large variety of biomarkers. In this work, we present a system enabling automated volumetric histology imaging of excised aortas that can spatially correlate results with combined IVUS/NIRF imaging of lipid-rich atheroma in cholesterol-fed rabbits. Pullbacks in the rabbit aortas were performed with a dual modality IVUS/NIRF catheter developed by our group. Ex vivo three-dimensional (3D) histology was performed combining optical coherence tomography (OCT) and confocal fluorescence microscopy, providing high-resolution anatomical and molecular information, respectively, to validate in vivo findings. The microscope was combined with a serial slicer allowing for the imaging of the whole vessel automatically. Colocalization of in vivo and ex vivo results is demonstrated. Slices can then be recovered to be tested in conventional histology.

Highlights

Atherosclerosis is a chronic immune-mediated inflammatory disease that arises from a series of complex events triggered by endothelial dysfunction, lipid accumulation in the arterial wall, and infiltration of monocyte-derived macrophages [1,2]
From the spatial resolution of optical coherence tomography (OCT), largely superior to Intravascular ultrasound (IVUS) [6], and the capacity of confocal fluorescence microscopy to efficiently identify the same molecular biomarkers as near-infrared fluorescence (NIRF) imaging [22], we developed a novel ex vivo automated 3D histology platform comprising a dual-modality imaging system based on OCT-coupled fluorescence sensitive confocal microscopy [21]
Placing the fluorophore bound to the intercellular adhesion molecule-1 (ICAM-1) antibody in the cell growth medium followed by flushing, it was observed that the signal was far more present for the TNF-alpha activated cells, suggesting that the ICAM-1 antibody does have affinity with inflammation (Figure 1)

Summary

Introduction

Atherosclerosis is a chronic immune-mediated inflammatory disease that arises from a series of complex events triggered by endothelial dysfunction, lipid accumulation in the arterial wall, and infiltration of monocyte-derived macrophages [1,2]. Conventional grayscale IVUS is, limited with regards to the analysis of plaque composition [9], whereas emerging molecular imaging technologies, such as fluorescence imaging, have been developed to overcome these limitations. Translation of molecular imaging results to clinical applications, requires validation; and despite impressive advances in intravascular imaging over the past decade, histology remains the gold standard for determining plaque composition and geometry. Providing high-resolution cross-sectional images of the arterial wall, histology remains limited to the number of tissue sections analyzed and by the lack of anatomical context; resulting in missed valuable data. When comparing in vivo intravascular imaging applications with histology, colocalization is often challenged by geometric distortions and tissue shrinkage, as well as the lack of anatomical landmarks and the limited resolution of IVUS imaging

Methods

Results

Conclusion