CT-pathologic correlation of non-calcified atherosclerotic arterial plaques: a study using carotid endarterectomy specimens

Abstract

Objective: Pathologic features of atherosclerotic plaques on CT are not established. We compared CT values among pathologically confirmed plaque constituents and evaluated their ability to distinguish plaque constituents.

Methods: 50 histopathological images of carotid endarterectomy samples from 10 males and 2 females (age 54-74 years, average 65.9 years) were examined. We compared pre-operative CT [pre-contrast (CT-P), early post-contrast phase (CT-E), delayed post-contrast phase (CT-D)] of lipid-rich necrotic core (NC) and fibrous tissue (F) plaque components with pathological images. The ability of features to differentiate plaque components using several discrimination techniques were compared.

Results: CT values of NC and F were 36 ± 13, 45 ± 11 (mean ± standard deviation, Hounsfield unit, HU), 41 ± 17, 69 ± 18, and 44 ± 16, 70 ± 13 in CT-P (p < 0.01), CT-E (p < 0.0001), and CT-D (p < 0.0001), respectively. The threshold, sensitivity, and accuracy for distinguishing NC from F were 44 HU, 74%, and 68%; 55 HU, 85%, and 85%; and 63 HU, 92%, and 84% in CTP, CT-E, and CT-D, respectively. CT-P had lower accuracy than CT-E and CT-D (both p < 0.05), but CT-E and CT-D were similar. CT-E and CT-D yielded 90 and 91% sensitivity and accuracy, respectively in linear discrimination analysis.

Conclusion: In both pre- and post-contrast CT, CT values were lower in NC than F. Although values overlapped, using two-phase post-contrast CTs improved discrimination ability.

Advances in knowledge: Our findings may help to establish computer-aided diagnosis of vulnerable atherosclerotic plaques in future.

Figure 1.

Plaque with lipid-rich necrotic core without hemorrhage in a 66-year-old female with transient ischemic attack. White circles show the region of interest. a: Carotid CT in the early postcontrast phase, b: The same level section stained with Masson trichrome (×10) shows a large lipid-rich necrotic core without hemorrhage in the carotid plaque. c: MRI of extracted tissue, d: CT image of extracted tissue, e: Precontrast CT image, f: Enhanced CT image in the early postcontrast phase, g: Enhanced CT image in the delayed postcontrast phase. The square in (a) indicates a position of (b)–(g).

Figure 2.

Plaque with lipid-rich necrotic core with hemorrhage in a 65-year-old male with transient ischemic attack. White circles show the region of interest. a: Carotid CT in the early postcontrast phase, b: Section histology, stained with Masson trichrome (×10) shows a large lipid-rich necrotic core with hemorrhage in the carotid plaque. c: MRI of extracted tissue, d: CT image of the extracted tissue, e: Pre-contrast CT image, f: Enhanced CT image in the early post-contrast phase, g: Enhanced CT image in the delayed postcontrast phase. The square in (a) indicates a position of (b)–(g).

Figure 3.

Plaque with rich fibrous tissue in a 54-year-old male with amaurosis fugax. White circles show the region of interest. a: Carotid CT in the early post-contrast phase, b: Histology stained with Masson’s trichrome (×10) shows large fibrous plaque with a thick fibrous cap. c: MRI of extracted tissue, d: CT image of extracted tissue, e: Precontrast CT image, f: Enhanced CT image in the early postcontrast phase, g: Enhanced CT image in the delayed postcontrast phase. The square in (a) indicates a position of (b)–(g).

Figure 4.

Scatter plot of NC (×) and F (o) using CT-E and CT-D. The linear line (y = −1.72x+152.2) shows the boundary line for the best linear discrimination. Dotted area shows a “double cut-off” area in Table 5 (CT-E ≤55 or CT-D ≤50). CT-D,enhanced CT in the delayed post-contrast phase; CT-E, enhanced CT in the earlypost-contrast phase; F, fibrous tissue; NC, lipid-rich necrotic core.