[Imaging techniques for showing the morphology and surface structure of extracranial internal carotid artery plaques]

Methods of determining plaques in the extracranial internal carotid artery are ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI). The goal of this overview is to introduce these methods and discuss their diagnostic and clinical significance. Ultrasound has the capability of showing the echogenity of the plaques. This method seems to demonstrate a relationship with the incidence of hemispheric symptoms. A histological association could only rarely be seen. The surface structure can only be clearly and correctly evaluated in individual cases under optimal circumstances. Computed tomography is capable of showing the calcium content and specific site of the plaques. However, lipid content and fibrous tissue cannot be deduced reliably. The currently available image resolutions limit a detailed imaging of surface characteristics. Magnetic resonance imaging provides, in vitro, a correct rendering of plaque composition and endoluminal surface structure. In vivo it is possible to recognize both the fibrous cap and necrotic core as well as intraplaque hemorrhage. Because of certain artefacts more detailed images are difficult to interpret. In conclusion, further clinical trials should reveal, whether these methods can be set in clinical routine to detect plaque surface and morphology for stratifying patients at risk of hemispheric symptoms during the spontaneous course as well as during carotid interventions.