Characterization of Carotid Plaque Components by Quantitative Susceptibility Mapping

Representative QSM (A) and MPRAGE (B) images of carotid plaques and corresponding histologic images (C–F) in a 77-year-old man. Carotid plaque with both hyper- and hypointense areas on the QSM image (A) and corresponding MPRAGE image (B). The hyperintense ROI (A, yellow outline) corresponds with histologic evidence of intraplaque hemorrhage and erythrocytes in the atherosclerotic necrotic core (C, H&E stain). The glycophorin-A-positive erythrocytes and erythrocyte fragments are abundant in the plaque (D). In the hyperintense ROI (yellow outline) on the QSM image (A), Prussian blue staining shows no iron deposition (E). Two hypointense ROIs (blue outline) on the QSM image (A) correspond with basophilic calcification in the plaque (F, H&E stain). The corresponding blue and yellow outlines are placed on the MPRAGE image (B).

Representative QSM image (A) of carotid plaques of a 79-year-old man and corresponding histologic images (B and C). Carotid plaque with a hyperintense area on the QSM image (A, red outline), which contained few GYPA-positive erythrocyte components in the corresponding histologic ROI (B, red outline). There are many intracellular hemosiderin deposits (blue) and a few erythrocytes (brown, arrow) in the ROI (C).

Correlative analysis of erythrocytes and iron deposits on histologic sections from a 73-year-old man (A–D) and the SV on the QSM image of whole plaque (E). Areas positive for GYPA staining (A) and color extraction (B) were relatively well-correlated with the distribution of hyperintensity on the QSM image (E). There are a few small areas positive for Prussian blue staining (C) and color extraction (D). Positively stained areas were extracted under specific protocols using the hue of the color and its lightness and saturation. Data are expressed as the ratio (percentage) of extracted green areas relative to the whole plaque (dashed outline in B and D). The ROI on the QSM image (yellow outline, E) is matched with the histologic ROI for measuring the mean SV of the whole plaque.

Comparison of the mean SV on QSM images (A) and the CR on MPRAGE images (B) among 4 typical atherosclerotic components. Analysis was with 1-way ANOVA with the Scheffe test (asterisk, P < .001; double asterisks, P < .01).