Ultrasonography of vulnerable atherosclerotic plaque in the carotid arteries: B-mode imaging

Abstract

The most common type of stroke, i.e. ischemic stroke, is a great challenge for contemporary medicine as it poses both diagnostic and therapeutic difficulties. Atherosclerosis, which is rapidly beginning to affect more and more social groups, is the main cause of cerebrovascular accidents. Atherosclerosis is currently defined as a generalized, dynamic and heterogeneous inflammatory and immune process affecting arterial walls. Atherosclerotic plaque is the emanation of this disease. As the paradigm of the diagnosis of atherosclerosis has changed, it has become crucial to properly identify plaque instability within the carotid arteries by evaluating parameters and phenomena that signify a developing cascade of complications, eventually leading to stroke. Irrespective of the ultrasound technique employed, proper morphological evaluation of atherosclerotic plaque, involving observation of its echogenicity, i.e. subjective analysis of its structure, with the classification to Gray-Weale-Nicolaides types as well as assessment of the integrity of its surface, makes it possible to roughly evaluate plaque morphology and thereby its stability. This enables treatment planning and therapy monitoring. This evaluation should be a prelude to further diagnostic work-up, which involves non-invasive examinations that enable unambiguous assessment of plaque stability. These examinations include contrast-enhanced ultrasound to assess progression or recession of inflammation, which presents as plaque neovascularization, or shear wave elastography to objectively define tissue stiffness, and thereby its mineralization.

The most common type of stroke, i.e. ischemic stroke, is a great challenge for contemporary medicine as it poses both diagnostic and therapeutic difficulties. Atherosclerosis, which is rapidly beginning to affect more and more social groups, is the main cause of cerebrovascular accidents. Atherosclerosis is currently defined as a generalized, dynamic and heterogeneous inflammatory and immune process affecting arterial walls. Atherosclerotic plaque is the emanation of this disease. As the paradigm of the diagnosis of atherosclerosis has changed, it has become crucial to properly identify plaque instability within the carotid arteries by evaluating parameters and phenomena that signify a developing cascade of complications, eventually leading to stroke. Irrespective of the ultrasound technique employed, proper morphological evaluation of atherosclerotic plaque, involving observation of its echogenicity, i.e. subjective analysis of its structure, with the classification to Gray-Weale–Nicolaides types as well as assessment of the integrity of its surface, makes it possible to roughly evaluate plaque morphology and thereby its stability. This enables treatment planning and therapy monitoring. This evaluation should be a prelude to further diagnostic work-up, which involves non-invasive examinations that enable unambiguous assessment of plaque stability. These examinations include contrast-enhanced ultrasound to assess progression or recession of inflammation, which presents as plaque neovascularization, or shear wave elastography to objectively define tissue stiffness, and thereby its mineralization.

Fig. 1.

Atherosclerotic plaque: a schematic

Fig. 2.

Atherosclerotic plaque evolution into vulnerable plaque (Virmani³⁴)

Fig. 3.

Uniformly echolucent plaque on the posterior wall of the LCCA (left common carotid artery). A. B-Mode. B. CFM mode. Author’s own material

Fig. 4.

Uniformly echolucent plaque on the posterior wall of the ICA (internal carotid artery). A. Plaque is visible thanks to flow visualization in a directional power Doppler examination. B. Plaque visualized in a volumetric examination. Author’s own material

Fig. 5.

Type (class) II plaque on the posterior wall of the CCA bifurcation. Author’s own material

Fig. 6.

Atherosclerotic plaque on the ICA anterior wall. A. Type II plaque, TCAP with elements of JBA (juxtaluminal black area) – blue arrow, and calcification – red arrow. B. Plaque visualized in a volumetric examination. Author’s own material

Fig. 7.

Mixed type II plaque. A. On the posterior wall of the CCA bifurcation, CFM image. B. On the ICA posterior wall – SMI (superb microvascular imaging). Author’s own material

Fig. 8.

Heterogeneous type III plaque. Authors’ own material

Fig. 9.

Type IV plaque; ICA flow with visible contrast enhancement. Authors’ own material

Fig. 10.

Completely calcified plaque. A. Acoustic shadow covers the field of view; B. B-Flow STIC imaging. C. CEUS. Author’s own material

Fig. 11.

Measurements. A. IMT; B. VWT. Author’s own material

Fig. 12.

Plaque ulceration. A. CFM image. B. SMI. C. Volumetric examination – surface rendering. Authors’ own material

Fig. 13.

Atherosclerotic plaque with smooth surface GWN IIIa. Authors’ own material

Fig. 14.

Atherosclerotic plaque with irregular surface GWN IIIb. Authors’ own material

Fig. 15.

Atherosclerotic plaque with ulceration GWN IIIc. Authors’ own material

Fig. 16.

Type IIIb plaque in the Gray-Weale–Nikolaides classification. Authors’ own material

Fig. 17.

Atherosclerotic plaque, CEUS. Authors’ own material

Fig. 18.

Atherosclerotic plaque, SWE. Authors’ own material