Automatic Evaluation of Carotid Stenosis Based on Computed Tomography Angiography

Atherosclerosis is a systemic disease, affecting individuals of all ages. It is characterized by the deposition of foreign elements in the arterial intima-media layer, leading to a gradual narrowing of the vascular lumen, impeding the blood flow. One of the possible consequences of atherosclerosis is transient ischemia or infarction of internal organs, including heart and brain.In the clinical practice, the diagnosis and evaluation of the progression of carotid atherosclerosis are usually performed by ultrasound imaging or computed tomography angiography. In both techniques, a large dependence on hand-operated assessment is present. To evaluate the stage of stenosis, a clinician has to take two measurements manually - the average lumen diameter, and the narrowest lumen diameter, i.e., where the plaque is located. The manual assessment of the carotid diameters does not guarantee reproducibility and repeatability of the results. It is also far from optimal due to the large chance of human error. An alternative approach is necessary.The thesis focuses on the development of a tool capable of reducing or even eliminating human dependency and possible errors that can occur during the manual assessment. A fully automatic tool - VASIM (Vascular Imaging) was developed. It uses reliable, fast, and simple methods, such as morphological operators both in 2D and in 3D, to segment the lumen volume and areas for stenosis calculation but also for the examination of vascular walls, plaque, and vessel-surrounding tissues. The section analyzed by VASIM encompasses the carotid arteries, one of the most common locations of atherosclerotic plaques in the arterial system. VASIM presents to the user not only the routinely used metrics but also new parameters. They are based on different tissues’ volumes, areas and progression throughout the arterial tree. Furthermore, VASIM creates 3D models, which could be used for surgery planning, plaque morphology and composition evaluation, and 2D linearization of all the components of the plaque.To validate VASIM, a clinical material of fifty-nine individuals, both healthy and suffering from atherosclerosis of the carotid arteries, was tested and analyzed. For cases with stenosis over 50%, VASIM had a clinical accuracy of 71%. The software prototype results suggest that this approach has potential in areas such as analysis of the atherosclerosis of carotid arteries and it could be applied in a clinical environment