Abstract 13377: Quantitative Assessment of Vulnerable Atherosclerotic Carotid Plaque: Comparison of Grating-Based X-Ray Phase Contrast Imaging and Histology

Abstract

Purpose Thin-cap fibrous atheromas, characterized by a large lipid-rich necrotic core (LR-NC) and a thin fibrous cap (FC), are associated with plaque rupture and cardiovascular events. Phase contrast imaging (PCI) is a novel x-ray technique exploiting the phase shift instead of absorption, allowing higher soft tissue contrast. The goal of this study was to assess whether PCI can differentiate and quantify important features of vulnerable plaques.

Material and Methods Five ex-vivo human carotid arteries were imaged by X-ray grating-based PCI using a conventional X-ray tube at a laboratory set up. After histology work up the slices were matched using anatomical landmarks. Quantitative measurements of FC area, FC thickness, LR-NC area and Calcium area (Ca) were collected from PCI images and histology sections.

Results A total number of 145 histology slices were available for analysis. Sixty-three (43%) areas with NC and an overlying fibrous cap and 75 (52%) areas with calcifications were identified by histology and PCI. There was an excellent correlation for LR-NC, FC and Ca area measurements by PCI and histology (r=0.92, r=0.93 and r= 0.90, respectively; all p<0.05). Total area measurements were significantly smaller in histology (p<0.05). There was no difference in area percentage of the total vessel wall area in PCI and histology measurements for LR-NC (22% v.s. 21%; p=0,18) , FC (10% vs. 9%; p=0.1) and Ca (6% vs. 5%; p=0.65), respectively.

Conclusion This study demonstrates that PCI with conventional X-ray tubes is capable of quantitatively measuring the dimensions of the intact FC, LR-NC and Ca. Ongoing studies will have to demonstrate whether this technique can be applied in vivo.