Carotid Artery Plaque Diagnosis Using CT

Carotid artery plaque diagnosis using CT is useful for detecting ulcer formation or calcified lesions through the spatial-resolution-based rearrangement of multiplanar images. Quantitative assessment, in which the plaque volume (mm3) is calculated, and qualitative assessment, in which plaque is classified into vulnerable or calcified plaque using the Hounsfield Unit (HU), are possible. Calcified plaque is clearly visualized on CT, with a high HU, and the grade of calcification can be evaluated. Carotid artery stenting (CAS) for carotid artery stenosis with marked calcification may not lead to sufficient dilation, and CT is useful for preoperative assessment. On the other hand, vulnerable plaque may show a low HU, and fresh post-CAS infarction/restenosis more frequently appear when the volume of plaque with a low HU is larger. However, in the presence of a hematoma in the site of vulnerable plaque with a low HU, the HU may increase; therefore, qualitative assessment is limited. Furthermore, the limitations of CT include renal toxicity related to the use of contrast medium, radiation exposure, and artifacts. However, CT is more advantageous than MRI from the viewpoints of exposure-time shortening and availability in case of emergency.