[Dual source computed tomography in analysis of significance and morphology carotid plaques]

One of the most common causes of stroke is carotid atherosclerosis, stroke affects about 60 thousand Polish people each year and about 27% of them die within a year. About 72%-86% are ischemic strokes, whereas intracerebral or subarachnoid haemorrhages account for about 9-18% of strokes. Stroke is the third most common cause of death worldwide, after heart disease and cancer, and the most often cause of chronic disability in people over 40. Carotid atherosclerosis is one of the most important stroke risk factors. The degree of stenosis is a standard parameter usually used in risk assessment. It was shown that patients with stenosis greater than 70% undergoing endarterectomy achieve the best results in reducing the risk of stroke compared with pharmacotherapy. However, it was found that in the general population of people over 64 the stenosis greater than 70% occurred in 10% of patients, while changes below 70% were very common and appeared in 70% of men and 60% of women. For this reason, the importance of atherosclerotic plaque morphology in the risk assessment is growing. Histopathological and ultrasound (intravascular ultrasound) morphological changes in the composition of the atherosclerotic plaque lead to the creation of the vulnerable plaque concept. Stroke risk seems to be connected with certain morphological features of the plaque, such as thin fibrous cap, lipid core, or ulceration. Ulceration is especially important, as 30% of those patients develop neurological symptoms within 2 years. On the other hand strong plaque calcification, particularly superficial, appears to pose lower risk. Ultrasound imaging of carotid arteries is currently the most widely used non-invasive diagnostic method for detecting and assessing the extent of carotid atherosclerosis. However, apart from undeniable advantages it also has its limitations such as the scope of the imaging and lower sensitivity and specificity in the evaluation of carotid stenosis in relation to magnetic resonance imaging and computed tomography (CT) as showed in metaanalyses from multicenter research (e.g. Chapel et al. metaanalysis). Previous studies using CT demonstrated the suitability of this method in the evaluation of morphology and significance of carotid arteries stenosis. Recent introduction of dual source multidetector computed tomography (DSCT) is a next technological step increasing the usefulness of CT in the assessment of plaque morphology. Due to simultaneous operation of 2 lamps the DSCT uses two concurrent X-ray sources (80 kv and 80 kV or 120 kV or 140 kV) to obtain different radiation absorption coefficients for a given tissue (in Hounsfield units). This allows for better tissue differentiation and advanced image processing, e.g. easy removal of bone parts for better visualization of vascular areas. This method also facilitates more accurate visualization of the lipid core and ulcerations. However, it should be emphasized that still relatively low spatial resolution of this method (0.6 mm) is a serious limitation to an accurate analysis of small structures, such as the components of the atherosclerotic plaque. Therefore, further comparative studies with other invasive diagnostic methods are necessary to improve the imaging protocols.