## 3 Results  
The purpose of this study was to identify unstable carotid artery plaques at risk of rupture by calculating an instability index. We took into account several potential markers of instability; the definitions or assessments were based on widely accepted descriptions of unstable plaques. Two grades of plaque instability were proposed (Table 1). Other clinical and biological risk factors present in the studied patients were not included in the assessment of the risk of instability. In patients' medical records, we found atherosclerotic risk factors: smoking (3/10 patients; 30%), hypertension (8/10 patients; 80%), dyslipidemia (5/10 patients, 50%), and diabetes (4/10 patients, 40%). The most relevant histological differences between stable plaque and unstable plaque are shown in Figure 1 (thick FCT versus thin FCT) and in Figure 2.  
The selected patients (eight males and two females, aged over 60 years) who underwent CEA exhibited carotid stenosis produced by ATS plaques. By analyzing histological plaque features, we identified various ATS plaques, such as stable, vulnerable or TCFA, and unstable,  
\begin{table} \begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Risk Factors**} & \multicolumn{2}{c}{**Score**} \\ \cline{2-3}  & **Grade 1** & **Grade 2** \\ \hline Age (years) & \textless{}70 & \textgreater{}70 \\ Sex & Female & Male \\ Fibrous Cap Thickness (FCT) & A band like FCT \textgreater{} 200 μm & \textless{}200 μm \\ Lipid core (LC) & Small LC \textless{} 2 mm\({}^{2}\) & Large LC \textgreater{} 2 mm\({}^{2}\) \\ CD68 & \textless{}50 cells & \textgreater{}50 cells \\ CD3 & \textless{}10 cells in cap & \textgreater{}10 cells in cap \\ CD31 & \textless{}20 per section & \textgreater{}20 per section \\ Calcium salts & Spotty only & Calcified nodules \\ IPH & Small amounts & Large amounts \\ Thrombin & Parietal & Occlusive \\ \hline \hline \end{tabular}  \(\Gamma\)  
==WARNING: Truncated because of repetitions==
(0) & (1) & (1) & (1) & (1) & (1) & (1) & (1) \\ Age & 75 & 67 & 60 & 60 & 73 & 63 & 68 & 71 & 67 & 61 \\  & (1) & (0) & (0) & (0) & (1) & (0) & (0) & (1) & (0) & (0) \\ FCT (\(\upmu\)M) & 948 & 1.115 & 468 & 552 & 351 & 7.7 & 41.6 & 2.45 & 101 & 15 \\  & (0) & (0) & (0) & (0) & (0) & (1) & (1) & (1) & (1) & (1) \\ LC (mm\({}^{2}\)) & 9.3 & 0.08 & 0.94 & 0.29 & 0.62 & 10.8 & 9.34 & 2.45 & \(-\) & 2.05 \\  & (1) & (0) & (0) & (0) & (0) & (1) & (1) & (0) & (1) \\  & 52 & 88 & 27 & 31 & 51 & 19 & 20 & 67 & 54 & 39 \\ CD68 \(>\) 50 & (1) & (1) & (0) & (0) & (1) & (0) & (0) & (1) & (1) & (0) \\ CD3 \(>\) 10 & 7 (0) & 9 (0) & 5 (0) & 6 (0) & 14 (1) & 11 (1) & 12 (1) & 8 (0) & 6 (0) & 4 (1) \\ CD31 \(>\) 20 & 38 & 20 & 18 & 14 & 9
+++  
exhibit instability, including thrombus at the site of plaque erosion. The molecular imaging methods can be used to identify fissures of the FC and consequent thrombosis. Our study emphasized the importance of histological plaque features in prognosis assessment. Our findings suggest that the size of fibrous cap thickness is a strong predictor of plaque instability [27]. In the analyzed samples, focal inflammation was a constant plaque feature, and previous reports found the macrophages were the main inflammatory cells [28]. The increased inflammatory state determines artery plaque instability [29; 30]. [PERSON] et al. noted that several types of inflammatory cells are identified in the carotid artery vulnerable plaque, and the presence of macrophages is significantly associated with the risk of plaque rupture [30]. In addition to macrophage accumulation, plaque fissures with superficial platelet aggregation are considered major criteria for plaque instability [31]. The state of chronic low-grade inflammation can contribute to the development of carotid plaque instability and stroke due to the activation of leucocytes. Inflammation promotes atheorthrombotic complications by enhancing platelet reactivity and predisposing to plaque rupture and erosion. Moreover, the atherosclerotic plaque infiltration with macrophages may enhance plaque angiogenesis [32].