Value of the CT angiography in the diagnosis of common carotid artery bifurcation disease: CT angiography versus digital subtraction angiography and color flow Doppler

Abstract

Objective: assessment of the degree of stenosis is the central point in the treatment of carotid stenosis. The purpose of our study was to assess whether invasive CT angiography (CTA) is a feasible alternative to the current invasive gold standard carotid digital subtraction angiography (DSA) and the current non-invasive gold standard color flow doppler. Subjects and methods: about 178 patients with cerebrovascular disease underwent digital subtraction angiography (DSA), CFD and CTA. CTA was performed on a Somatom plus 4 (Siemens, Erlangen Germany). CT was performed with 2/3/2 (collimation/table feed/reconstruction interval) or 2/3/1 mm, start delay 15–20 s, flow 2.5–3.0 ml/s, using 120 ml non-ionic contrast medium (300 mg J/ml). Quantification of degree of stenosis was based on the perfused area in the axial slices. Plaque morphology (soft and hard) and ulceration were evaluated. Results: CTA detected nine cases of significant stenosis, which had been underestimated by DSA. CTA failed in two cases of a membraneous stenosis, which were underestimated, and in two cases with teeth artifacts. Calcifications were more readily appreciated by CTA than in CFD. In this respect, both methods were superior to DSA. CFD, DSA and CTA had a sensitivity of 100% for occlusions, respectively. Conclusion: CT angiography is useful in case of inconclusive CFD in the pre- and postoperative phase, and as a third modality in case of disagreement between DSA and CFD.

Introduction

Ischemic cerebral vascular disease is second to coronary heart disease the most frequent reason of death due to atherosclerotic disease. Symptomatic patients with high grade stenosis of the carotids draw profit from carotid thrombendarterectomy. The North American Symptomatic Carotid Endarterectomy Trial (NASCET) reported a reduction in the risk of an ipsilateral stroke of 17% at 2 years in patients with greater than 70% carotid stenosis, who were treated surgically in comparison to patients treated medically [1], [2]. The European Carotid Surgery Trial (ECST) showed a benefit for men with a stenosis of 80%(NASCET 60–70%) and for women with a stenosis of 90%(NASCET 70–80%)[3], [4]. The Asymptomatic Carotid Atherosclerosis Study [5], [6] showed that even asymptomatic patients with carotid stenosis of 60% or more drew benefit from surgery with low risk. Catheter angiography is the accepted gold standard to assess the carotids, but the risks and costs of this modality must be considered [7], [8], [9], [10]. Non-invasive modalities like duplex sonography, color flow doppler, MR and CT angiography have also emerged and are more and more considered as a potential substitute for DSA. Doppler and color flow doppler are the screening methods, they are cost-efficient and have a good reliability [8], [11], [15]. In comparison with the doppler CTA needs and MRA should be done by the application of contrast agents. MRA had the tendency to overestimate the degree of stenosis, although progress has been made in that respect with gadolineum enhanced gradient-echo imaging [12], [13]. Nevertheless, CFD, CTA and MRA may have false-positive and false-negative results in diagnosing carotid stenosis and occlusions [13], [14], [15]. The purpose of the present study was to assess the diagnostic performance of non-invasive CT angiography and to further define its role in the diagnostic algorithm of cerebrovascular disease.