Preoperative Assessment for Carotid Artery Stenosis: Utility of a Combined Diagnostic Approach by Dynamic MRA and CTA

Abstract

Dynamic Magnetic Resonance Angiography (MRA) and Computed Tomography Angiography (CTA) represent two non-invasive techniques which can perform a pre-therapeutic evaluation of carotid artery disease. Ultrasound (US) is the screening technique for this type of pathology and after US results, surgeons or endovascular therapists need more information for a correct therapeutic approach. We performed a combined diagnostic approach with CTA and dynamic MRA to reduce the need for DSA in which permanent and transitory neurological side effects are still possible and to evaluate the efficacy of these two diagnostic modalities. We performed dynamic MRA and CTA in 80 patients with carotid disease in which a US examination showed the presence of more than 60% stenosis. Dynamic MRA was performed with a 3D coronal volumetric acquistion with a dedicated head-neck coil, 2.5 mm thickness and 18 s acquisition time after contrast media injection to obtain only the visualization of the arterial phase from the origin of the epiaortic vessels through the bifurcation of the siphon without overlap with the venous phase. CTA was done with a spiral technique with contrast media injection (120 ml- 3ml/s) from C6 through the skull base. In 60 patients, we found the same degree of stenosis between carotid CTA and US examination. In eight cases, US showed an occlusion of the internal carotid artery (ICA) while CTA reported severe stenosis between 85–90%. Two cases showed a 85% stenosis of the ICA, while CTA and dynamic MRA disclosed ICA occlusion. CTA showed parietal thrombus and arterial wall calcifications very well. Dynamic MRA overestimated the stenosis in 85% of the patients, almost always in patients with a stenosis greater than 65–70% and in seven cases also showed an abnormal signal intensity of the origin of the epiaortic vessels or of the intracavernous segment of the ICA that was confirmed by DSA only in four patients. With three patients, it was not possible to perform CTA or MRA because of incorrect transit time evaluation or poor patient cooperation. The combined diagnostic approach by CTA and Dynamic MRA can be adequate to give a correct pre-therapeutic evaluation in patients with carotid disease; in doubtful or uncooperative cases, DSA is still required.