L'angioscanographie helicoidale 3D dans la caracterisation de la stenose carotidienne

Angio-CT is a minimally invasive, useful diagnostic method for the evaluation of diseases of the carotid bifurcation. Necessary technical conditions are: spiral scans with a 2-3 mm/sec table speed, 2 mm beam collimation, 1 mm reconstruction and IV iodinated contrast material injected at 2.5 ml/sec. Information is provided by axial images, shaded surface display (SSD), multiplanar curved reformations and maximum intensity projection (MIP). Multiplanar curved reconstructions are particularly useful for CT-density plaque characterization. Angio-CT is multiplanar and allows characterization of plaques with respect to calcification, fatty content, fibrosis, ulceration, and size that cannot be obtained with conventional angiography. The assessment of CT-plaque density is quantitative but quantitative texture analysis of CT-angiographic defined plaques has still to be done and to be correlated with clinical risk. CT angiography can visualize angiographically defined ulcerations of more than 1 mm size, but fails to visualize fine (< 1 mm) intimal ruptures. Comparing low invasive methods, angio-MRI is very sensitive for the detection of fat, but has low sensitivity for calcifications (contrary to CT); with respect to a combination of Doppler and B-ultrasound, angio-CT has probably a lesser sensitivity for the identification of fresh thrombi, but shows the 3D-aspect of plaques. We need still more data on comparison between different imaging modalities with respect to plaque characterisation and associated risks, but angio-CT and ultrasound can be used in most cases for exploration of carotid bifurcation.