CE-CTA appears ready for routine internal carotid artery imaging

Taiwanese researchers have found that contrasted-enhanced multidetector CT angiography is a perfect match for conventional angiography in differentiating between total and near-total occlusive disease and mapping the architectural landmarks of the internal carotid artery (ICA)

Dr. Hui-Ling Hsu and colleagues at Ching Gun Min Hospital in Taipai identified extraordinary concordance between the two techniques in a study of 512 symptomatic patients. Results were reported in a scientific session at the RSNA meeting on Wednesday.

Fifty-seven ICA total or near-total occlusions identified by conventional angiography were studied with MDCT angiography performed on a four-slice machine one to three days after conventional angiography.

During the CTA exams, 1.25-mm slices were acquired, achieving coverage of the internal carotid arteries from the carotid bifurcation to the circle of Willis. Data acquisition was performed after a bolus injection of noniodinated contrast agent at a flow rate of 3 mL per second. Two radiologists interpreted the images.

MDCT far outperformed duplex ultrasound, which in a previous study had achieved a specificity of 86% and 94% for uncovering total and partial ICA occlusion, respectively, Hsu said.

Both CE-CTA and the angiographic gold standard depicted 31 total occlusions, including 10 without a stump, 19 with a stump less than 2 cm, and two with a stump greater than 2 cm. Among them, 22 had downward extent of the intracranial ICA reconstitution flow at or above the carotid siphon, eight at the carotid canal, and one at the distal cervical ICA, he said.

The two modalities depicted 26 near-occlusions, including 21 proximal-third high-grade stenoses, one middle-third high-grade stenosis, two distal high-grade stenoses, and two diffusely hypoplastic lumens along the cervical ICA.

There was 100% agreement between CE-CTA and conventional angiography for depiction of all total and near-total occlusions with no inter-rater variance. CTA scored perfect specificity and sensitivity levels for correctly characterizing the occlusive level and downward extent of the intracranial ICA reconstitution flow in all occlusions.

Not surprisingly, Hsu concluded that MDCT can substitute for conventional angiography in confirming the results of ultrasound for diagnosing ICA occlusions.