CT angiography ofthe carotid arteries.

ABSTRACT

The introduction of multislice scanning has made CT angiography (CTA) a serious competitor to MR angiography (MRA) as a second line method for the evaluation of the carotid arteries. For optimum display of the morphology of stenoses, it is necessary to apply the thinnest possible section collimation (ideally [symbol see text] 1.25mm). While the scan range is limited for single slice CTA, it is possible to cover the whole supraaortic circulation from the aortic arch to the intracranial vessels using multislice scanning. Timing of contrast injection is important, however, the injection technique for carotid CTA is more forgiving than for other body regions. Image evaluation is mainly based on axial sections and curved planar reformations (CPR). Other techniques only serve as an adjunct to better be able to demonstrate the findings. Most potential pitfalls can be avoided by using the appropriate technique. CTA has been shown to have a pooled sensitivity of 95% and specificity of 98% for the detection of >70% stenoses, even if only older single-slice techniques are used. Differentiation between lipid, fibrous and calcified plaques may be possible, especially with multislice scanning. Multislice CTA can in addition detect tandem stenoses in the region of the carotid origin from the aorta, the carotid siphon, and the intracranial portion of the carotids. CT is able to provide a comprehensive evaluation of patients with acute stroke by using a combined approach of pre-contrast CT to detect hemorrhage and manifest infarction, CT brain perfusion measurements to differentiate between penumbra and infarct and CTA to detect the occluded vessel as well as potential concomitant carotid abnormalities. In summary, carotid CTA has come of age and can be used to quantify stenoses more precisely than ultrasound, to detect tandem stenoses and for the workup of acute stroke patients. The learning objectives include learning how to chose acquisition parameters for carotid CTA, how to process and interpret carotid CTA, to become familiar with the artifacts and pitfalls of carotid CTA, and to comprehend the role of CTA relative to the other modalities for carotid imaging.