High-concentration contrast media (HCCM) in CT angiography of the carotid system: impact on therapeutic decision making

Abstract

CT angiography (CTA) is a minimally invasive technique that enables precise delineation of extracranial and intracranial vascular anatomy and pathology based on high intravascular density. With a 64-slice MDCT scanner, improved first-pass vascular visualization can be obtained with HCCM (400 mg I/ml) using 25 ml for combined intra-and extracranial studies and 20 ml for intracranial examinations alone. We reviewed 23 patients with extra-cranial stenoocclusive disease and 12 patients with intra-cranial aneurysms. Two additional patients presented with a mycotic aneurysm and a micro arteriovenous malformation (micro-AVM). In 23 patients with 27 significant (> or =70%) vascular stenoses, high intraluminal contrast density and optimal projection of the stenosis profile facilitated precise delineation of the residual lumen in all vessels affected. Pseudoocclusion was present in 3 of the 27 vessels (11%) and ulceration in 5 (18.5%). CTA, in contrast to digital subtraction angiography (DSA) and magnetic resonance angiography (MRA), was able to delineate the mural constituents of stenoses, particularly marked calcification (present in 17 of 27 vessels, 62.9%). Eccentric vessel wall narrowing indicated dissection in three vessels (11%) and circular postradiation fibrosis was found in two vessels (7.4%). High-quality CTA obviated the need for DSA for diagnostic purposes in every patient. The decision regarding surgical treatment in nine vessels (33%) was influenced by the location of the stenosis relative to the carotid bifurcation, the length of the stenosis, and the level of the carotid bifurcation. Endovascular treatment in 12 vessels (44.4%) and the appropriate choice and placement of endovascular devices was affected by the anatomic configuration of the supraaortic vessels, and by the intrastenotic dimensions relative to the dimensions of the vessel proximal and distal to the stenosis. The anatomic availability of collaterals, relevant for both treatments, was determined via the anterior communicating artery (ACoA) in 91.3% of patients and the posterior communicating artery (PCoA) in 80.4% of patients. Intracranial CTA displayed the lesion location, configuration, size, and orientation in each of the 12 patients with intracranial aneurysms and in the two patients with a micro-AVM and a mycotic aneurysm. The correct diagnosis was established prior to DSA in each patient. Following CTA, the role of DSA was relegated to endovascular therapy in three aneurysms. For surgical candidates, DSA served to exclude potential multiplicity in ten saccular aneurysms and in one mycotic aneurysm. CTA provided information supplementary to DSA in 11 of the 13 aneurysms (84.6%). Delineation of blebs, calcification, thrombus, or incorporation of branches facilitated risk stratification with respect to rupture and to surgical or endovascular treatment. Advantages of CTA, such as virtual independence from the hemodynamic situation, delineation of landmarks and vessel wall calcification, and the ability to quantify vessels and aneurysms, distinguish this technique from other noninvasive vascular imaging techniques and DSA. Acquired with the use of iodinated HCCM, CT angiograms permit excellent recognition of appropriate diagnostic and interventional treatment paths, thereby facilitating improved decision-making regarding endovascular or surgical treatment.