Ex vivo differential phase contrast and magnetic resonance imaging for characterization of human carotid atherosclerotic plaques
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Non-invasive detection of specific atherosclerotic plaque components related to vulnerability is of high clinical relevance to prevent cerebrovascular events. The feasibility of magnetic resonance imaging (MRI) for characterization of plaque components was already demonstrated. We aimed to evaluate the potential of ex vivo differential phase contrast X-ray tomography (DPC) to accurately characterize human carotid plaque components in comparison to high field multicontrast MRI and histopathology. Two human plaque segments, obtained from carotid endarterectomy, classified according to criteria of the American Heart Association as stable and unstable plaque, were examined by ex vivo DPC tomography and multicontrast MRI (T1-, T2-, and proton density-weighted imaging, magnetization transfer contrast, diffusion-weighted imaging). To identify specific plaque components, the plaques were subsequently sectioned and stained for fibrous and cellular components, smooth muscle cells, hemosiderin, and fibrin. Histological data were then matched with DPC and MR images to define signal criteria for atherosclerotic plaque components. Characteristic structures, such as the lipid and necrotic core covered by a fibrous cap, calcification and hemosiderin deposits were delineated by histology and found with excellent sensitivity, resolution and accuracy in both imaging modalities. DPC tomography was superior to MRI regarding resolution and soft tissue contrast. Ex vivo DPC tomography allowed accurate identification of structures and components of atherosclerotic plaques at different lesion stages, in good correlation with histopathological findings.
KeywordsX-rays Synchrotron Differential phase contrast Magnetic resonance imaging Carotid plaque Atherosclerosis
Differential phase contrast
Magnetic resonance imaging
Magnetization transfer contrast
Lumen of the blood vessel
The authors are grateful to Dr. Bernd R. Pinzer and Sabina Wunderlin for technical support. The Scientific Center for Optical and Electron Microscopy (ScopeM) of the ETH Zurich is acknowledged for support. We thank the surgeon Zoran Rancic (Z.R.) from the Clinic for Cardiovascular Surgery, University Hospital Zurich, for the initial macroscopic classification of the plaques. The team of Prof. Philipp A. Kaufmann from the Department of Nuclear Medicine, Cardiac Imaging, University Hospital Zurich, is acknowledged for coordinating the plaque collection.
Compliance with Ethical Standards
Conflict of interest
This work was financially supported by the Clinical Research Priority Program (CRPP) of the University of Zurich on Molecular Imaging (MINZ) and the Swiss National Science Foundation (Grant PZ00P3_136822 to J.K.).
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