Characteristics Of The Carotid Atherosclerotic Plaque

A major cause for the occurrence of stroke or TIA is atherosclerosis. Currently, the degree of the carotid artery stenosis is an important factor to select patients for a carotid endarterectomy (CEA). New imaging techniques such as MDCTA and MRI have made it possible to look in detail at the atherosclerotic plaque. This allows us to see which components (for example hemorrhage, calcifications, lipid core) are present in the atherosclerotic plaque. The exact plaque composition could help to determine which people have a higher risk of getting a recurrent stroke and could have an important impact on the choice of treatment. The PARISK study aims to answer the question which plaque characteristics – assessed with ultrasound, MDCTA and MRI – are associated with an increased risk of recurrent stroke. At this moment, final follow-up measurements are performed to answer this question. For now, we tried to get a better understanding of what happens in an atherosclerotic plaque and the role of blood clotting in atherosclerosis. Moreover, we looked at which imaging techniques and which plaque characteristics can be valuable in future clinical practice. A few examples of the topics discussed in this thesis: 1. Von Willebrand Factor (VWF) and ADAMTS13 are involved in blood clotting and previous research has shown that these blood biomarkers are also associated with an increased risk of cardiovascular disease. Atherosclerosis may play a role in this association. We investigated whether we could prove this hypothesis, unfortunately the precise mechanism of the relationship between VWF and ADAMTS13 and the risk of cardiovascular disease remains unknown. 2. In the PARISK study various imaging techniques to image the carotid artery are used. We have found a link between the presence of hemorrhage in the atherosclerotic plaque on MRI and plaque ulceration on MDCTA. In addition, we found that MRI plaque imaging techniques presently cannot be recommended to estimate volume of plaque calcifications in individual patients, and that giving a contrast medium in ultrasound can have additional value to assess plaque ulcerations

Association between Intraplaque Hemorrhage and Vascular Remodeling in Carotid Arteries: The Plaque at RISK (PARISK) Study

Introduction: Vascular remodeling is a compensatory enlargement of the vessel wall in response to atherosclerotic plaque growth. We aimed to investigate the association between intraplaque hemorrhage (IPH), vascular remodeling, and luminal dimensions in recently symptomatic patients with mild to moderate carotid artery stenosis in which the differences in plaque size were taken into account. Materials and Methods: We assessed vessel dimensions on MRI of the symptomatic carotid artery in 164 patients from the Plaque At RISK study. This stud

Plaque composition as a predictor of plaque ulceration in carotid artery atherosclerosis: The plaque at RISK study

BACKGROUND AND PURPOSE: Plaque ulceration is a marker of previous plaque rupture. We studied the association between atherosclerotic plaque composition at baseline and plaque ulceration at baseline and follow-up. MATERIALS AND METHODS: We included symptomatic patients with a carotid stenosis of ,70% who underwent MDCTA and MR imaging at baseline (n=180). MDCTA was repeated at 2 years (n=73). We assessed the presence of ulceration using MDCTA. Baseline MR imaging was used to assess the vessel wall volume and the presence and volume of plaque components (intraplaque hemorrhage, lipid-rich necrotic core, and calcifications) and the fibrous cap status. Associations at baseline were evaluated with binary logistic regression and reported with an OR and its 95% CI. Simple statistical testing was performed in the follow-up analysis. RESULTS: At baseline, the prevalence of plaque ulceration was 27% (49/180). Increased wall volume (OR = 12.1; 95% CI, 3.5-42.0), higher relative lipid-rich necrotic core (OR= 1.7; 95% CI, 1.3-2.2), higher relative intraplaque hemorrhage volume (OR= 1.7; 95% CI, 1.3-2.2), and a thin-or-ruptured fibrous cap (OR = 3.4; 95% CI, 1.7-6.7) were associated with the presence of ulcerations at baseline. In 8% (6/73) of the patients, a new ulcer developed. Plaques with a new ulceration at follow-up had at baseline a larger wall volume (1.04 cm3 [IQR, 0.97-1.16 cm3] versus 0.86 cm3 [IQR, 0.73-1.00 cm3]; P=.029), a larger relative lipid-rich necrotic core volume (23% [IQR, 13-31%] versus 2% [IQR, 0-14%]; P=.002), and a larger relative intraplaque hemorrhage volume (14% [IQR, 8-24%] versus 0% [IQR, 0-5%]; P<.001). CONCLUSIONS: Large atherosclerotic plaques and plaques with intraplaque hemorrhage and lipid-rich necrotic cores were associated with plaque ulcerations at baseline and follow-up

Hand exoskeleton structure for interacting with virtual objects

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Joint intensity-and-point based registration of free-hand B-mode ultrasound and MRI of the carotid artery

Purpose: To introduce a semiautomatic algorithm to perform the registration of free-hand B-Mode ultrasound (US) and magnetic resonance imaging (MRI) of the carotid artery. Methods: The authors' approach combines geometrical features and intensity information. The only user interaction consists of placing three seed points in US and MRI. First, the lumen centerlines are used as landmarks for point based registration. Subsequently, in a joint optimization the distance between centerlines and the dissimilarity of the image intensities is minimized. Evaluation is performed in left and right carotids from six healthy volunteers and five patients with atherosclerosis. For the validation, the authors measure the Dice similarity coefficient (DSC) and the mean surface distance (MSD) between carotid lumen segmentations in US and MRI after registration. The effect of several design parameters on the registration accuracy is investigated by an exhaustive search on a training set of five volunteers and three patients. The optimum configuration is validated on the remaining images of one volunteer and two patients. Results: On the training set, the authors achieve an average DSC of 0.74 and a MSD of 0.66 mm on volunteer data. For the patient data, the authors obtain a DSC of 0.77 and a MSD of 0.69 mm. In the independent set composed of patient and volunteer data, the DSC is 0.69 and the MSD is 0.87 mm. The experiments with different design parameters show that nonrigid registration outperforms rigid registration, and that the combination of intensity and point information is superior to approaches that use intensity or points only. Conclusions: The proposed method achieves an accurate registration of US and MRI, and may thus enable multimodal analysis of the carotid plaque