Value of the CT angiography in the diagnosis of common carotid artery bifurcation disease: CT angiography versus digital subtraction angiography and color flow Doppler
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.
Section snippets
Methods and patients
In a prospective controlled study, 178 patients with cerebrovascular disease underwent color flow Doppler (CFD), digital subtraction angiography (DSA) and CT angiography (CTA) of the supraaortal vessels between 11/96 and 12/99. About 105 patients were male, 73 female; age from 42 to 85 years (mean 68 years), 163 in the preoperative and 15 in the postoperative phase.
CTA was performed on a Somatom Plus 4 spiral CT scanner(Siemens, Erlangen, Germany). All patients received 120 ml of iodinated 300
Results
In 178 patients with cerebrovascular insufficiency, there were 236 cases of severe stenosis of the carotid bifurcation, regarding the internal carotid artery in 171 cases, the external carotid artery in 48 cases and the common carotid artery in 17 cases. All the patients with a high grade stenosis of the ICA and the CCA were operated within the following days, so we could review the results of the three modalities.
CTA demonstrated 232 of the 236 stenoses (sensitivity, 98.3%). In two cases,
Discussion
Vessels running primarily in the longitudinal plane of scanning are especially suited, but vessels with an angled course are also amenable to helical CT [17]. However, also vessels with a horizontal orientation (renal arteries) can be analyzed in high quality [18]. In our study, occlusions of carotids could be detected with a sensitivity of 100% in two modalities. Other authors [15], however, have reported difficulties with CFD and MRA. In the assessment of dissection [19], CTA is a very useful
Conclusion
CTA is a useful, feasible and precise non-invasive method for the work-up of the carotids. It is comparable or better to the current gold standard DSA in being able to quantify the degree of stenosis of the carotid bifurcation, and it is also superior to operator-dependent CFD.
CFD is the best screening method and most cost-effective. In the case of an inconclusive CFD in the pre- and postoperative phase assessing the carotid bifurcation, CTA should be used and DSA should be discontinued. CTA
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