Sietske Rozie

Erasmus Universiteit Rotterdam, Rotterdam, South Holland, Netherlands

Are you Sietske Rozie?

Claim your profile

Publications (15)48.04 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The distensibility of a blood vessel is a marker of atherosclerotic disease. In this paper we investigate the feasibility of measuring carotid artery distensibility on 4D CTA, both manually and using a new automatic method. On 4D CTA datasets manual (n=38) and automatic (n=76) measurements of the carotid distensibility were performed. A subset (n=10) of the manual annotations were repeated by a second observer. The interobserver variability was assessed using a Bland-Altman analysis and appeared to be too large to reliably measure the distensibility using manual annotation. We compared two versions of the automatic method: one using 3D registration and one using a 4D registration method. The latter resulted in a more smooth deformation over time. The automatic method was evaluated using a synthetic deformation and by investigating whether known relations with cardiovascular risk factors could be reproduced. The relation between distensibility and cardiovascular risk factors was tested with a Mann-Whitney U test. Automatic measurements revealed an association with hypertension whereas the manual measurements did not. This relation has been found by other studies too. We conclude that carotid artery distensibility measurements should be performed automatically and that the method described in this paper is suitable for that. All CTA datasets and related clinical data used in this study can be downloaded from our website (http://ctadist.bigr.nl).
    Medical image analysis 03/2013; 17(5):515-524. · 3.09 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to validate automated atherosclerotic plaque measurements in carotid arteries from CT angiography (CTA). We present an automated method (three initialization points are required) to measure plaque components within the carotid vessel wall in CTA. Plaque components (calcifications, fibrous tissue, lipids) are determined by different ranges of Hounsfield Unit values within the vessel wall. On CTA scans of 40 symptomatic patients with atherosclerotic plaque in the carotid artery automatically segmented plaque volume, calcified, fibrous and lipid percentages were 0.97 ± 0.51 cm(3), 10 ± 11%, 63 ± 10% and 25 ± 5%; while manual measurements by first observer were 0.95 ± 0.60 cm(3), 14 ± 16%, 63 ± 13% and 21 ± 9%, respectively and manual measurement by second observer were 1.05 ± 0.75 cm(3), 11 ± 12%, 61 ± 11% and 27 ± 10%. In 90 datasets, significant associations were found between age, gender, hypercholesterolemia, diabetes, smoking and previous cerebrovascular disease and plaque features. For both automated and manual measurements, significant associations were found between: age and calcium and fibrous tissue percentage; gender and plaque volume and lipid percentage; diabetes and calcium, smoking and plaque volume; previous cerebrovascular disease and plaque volume. Significant associations found only by the automated method were between age and plaque volume, hypercholesterolemia and plaque volume and diabetes and fibrous tissue percentage. Significant association found only by the manual method was between previous cerebrovascular disease and percentage of fibrous tissue. Automated analysis of plaque composition in the carotid arteries is comparable with the manual analysis and has the potential to replace it.
    The international journal of cardiovascular imaging 05/2011; 28(4):877-87. · 2.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Intracranial arterial stenosis (ICAS) in patients with recent ischemic stroke is associated with a high risk of recurrent stroke. More insight into the pathophysiology of ICAS could help identify patients at high risk requiring more aggressive secondary prevention. We evaluated the prevalence, distribution, calcification, and the risk factors predisposing ICAS in a European stroke population. Consecutive patients with a transient ischemic attack or ischemic stroke (n=786) were evaluated for the presence and distribution of ICAS (≥30% luminal narrowing) by CT angiography. ICAS were categorized as symptomatic or asymptomatic, and the presence of calcification was assessed. The association of traditional cerebrovascular risk factors and the erythrocyte sedimentation rate with ICAS was analyzed. In 178 of 786 patients (23%), 288 ICAS were observed. Most stenoses (n=194/288; 67%) were located in the posterior circulation arteries. In 59 of 786 patients (8%), ICAS were considered symptomatic. ICAS in the basilar artery and arteries beyond the circle of Willis were mainly noncalcified. In addition to age, gender, and several traditional cerebrovascular risk factors, erythrocyte sedimentation rate was independently associated with the presence of ICAS (OR, 1.20; 95% CI, 1.06-1.36) and with the presence of noncalcified ICAS in particular (OR, 1.20; 95% CI, 1.05-1.37). ICAS was observed in a noteworthy number of European stroke patients. Particularly, the majority of ICAS was observed in the posterior circulation, possibly conferring worse prognosis. ICAS in distal arteries were mainly noncalcified. Association of noncalcified ICAS and erythrocyte sedimentation rate may indicate a prominent role for inflammatory factors in intracranial atherosclerotic disease.
    Stroke 03/2011; 42(5):1244-50. · 6.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Symptomatic carotid artery plaque ulceration is associated with distinct plaque components such as a large lipid-rich necrotic core (LR-NC) in ischemic stroke patients with a ≥50% carotid stenosis. We evaluated the associations between carotid artery plaque ulceration and plaque characteristics in ischemic stroke patients with ≥50% stenosis, as well as in those with a low degree of stenosis (0% to 49%). Consecutive patients (n=346) with symptoms in the anterior circulation were evaluated with multidetector CT angiography (MDCTA) for the presence of atherosclerotic plaque, degree of stenosis, and plaque ulceration in the symptomatic carotid artery. Plaque volume and plaque component proportions of LR-NC, fibrous tissue, and calcification were measured. The associations between plaque ulceration and plaque characteristics were analyzed using logistic regression. Atherosclerotic plaque was present in 185 patients. Plaque ulcerations were present in 38 (21%) patients, of which half had a low degree stenosis (0% to 49%). Plaque volume was significantly larger in ulcerated plaques. After adjustment for age, sex, and degree of stenosis, LR-NC proportion was strongly associated with plaque ulceration (odds ratio, 2.21; 95% CI, 1.49 to 3.27), whereas calcification proportion was inversely associated with plaque ulceration (odds ratio, 0.60; 95% CI, 0.40 to 0.89). These associations remained significant in patients with a low degree stenosis (0% to 49%). Plaque volume, degree of stenosis, and LR-NC proportion evaluated noninvasively with MDCTA are associated with carotid artery plaque ulceration, even in patients with a low degree stenosis (0% to 49%). Plaque volume and composition analysis with MDCTA may identify rupture prone plaques and improve risk stratification in ischemic stroke patients.
    Stroke 02/2011; 42(2):367-72. · 6.16 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Atherosclerotic carotid plaque rupture may lead to thromboembolization, causing transient ischemic attack or ischemic stroke. Carotid plaque ulceration on angiography is associated with plaque rupture. Although healing of ruptured plaques has been described in coronary arteries, little is known about the natural development of plaque ulcerations in carotid arteries. We therefore explored the evolution of carotid plaque surface morphology with serial multidetector CT angiography (MDCTA). From a registry of patients with transient ischemic attack or minor ischemic stroke, we selected 83 patients who had undergone serial MDCTA of the carotid arteries. Arteries subjected to revascularization procedures between the two scans were excluded (n = 11). Plaque surface morphology was classified as smooth, irregular or ulcerated on both baseline and follow-up MDCTA. Progression (i.e. development of irregularities or ulceration) and regression (i.e. disappearance of irregularities or ulceration) in morphology were evaluated. The mean time interval between the MDCTA scans was 21 ± 13 months. At baseline, 28 (18%) arteries were normal, 124 (80%) contained atherosclerotic plaque and 3 (2%) were occluded. Plaque surface morphology was smooth in 86 arteries (55%), irregular in 23 (15%) and ulcerated in 15 (10%). At follow-up, surface morphology was unchanged in 88% of arteries, had progressed in 8% and regressed in 4%. Most importantly, plaque morphology remained unchanged in most ulcerated plaques (10/15; 67%). One ulcerated plaque had progressed, whereas 4 had regressed. New ulcerations had developed in 2 nonulcerated plaques. MDCTA allows evaluation of temporal changes in atherosclerotic carotid plaque morphology. Plaque surface morphology remained unchanged in most arteries. Carotid ulcerations persist for a long time, and may remain a potential source of thromboembolism.
    Cerebrovascular Diseases 01/2011; 31(3):263-70. · 2.81 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper describes an evaluation framework that allows a standardized and objective quantitative comparison of carotid artery lumen segmentation and stenosis grading algorithms. We describe the data repository comprising 56 multi-center, multi-vendor CTA datasets, their acquisition, the creation of the reference standard and the evaluation measures. This framework has been introduced at the MICCAI 2009 workshop 3D Segmentation in the Clinic: A Grand Challenge III, and we compare the results of eight teams that participated. These results show that automated segmentation of the vessel lumen is possible with a precision that is comparable to manual annotation. The framework is open for new submissions through the website http://cls2009.bigr.nl.
    Medical image analysis 01/2011; 15:477-488. · 3.09 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a level set based method for segmenting the outer vessel wall and plaque components of the carotid artery in CTA. The method employs a GentleBoost classification framework that classifies pixels as calcified region or not, and inside or outside the vessel wall. The combined result of both classifications is used to construct a speed function for level set based segmentation of the outer vessel wall; the segmented lumen is used to initialize the level set. The method has been optimized on 20 datasets and evaluated on 80 datasets for which manually annotated data was available as reference. The average Dice similarity of the outer vessel wall segmentation was 92%, which compares favorably to previous methods.
    Anesthesiology 01/2011; 7962. · 5.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We propose and validate a semi-automatic method for lumen segmentation of the carotid bifurcation in computed tomography angiography (CTA). First, the central vessel axis is obtained using path tracking between three user-defined points. Second, starting from this path, the segmentation is automatically obtained using a level set. The cost and speed functions for path tracking and segmentation make use of intensity and homogeneity slice-based image features. The method is validated on a large data set of 234 carotid bifurcations of 129 ischemic stroke patients with atherosclerotic disease. The results are compared to manually obtained lumen segmentations. Parameter optimization is carried out on a subset of 30 representative carotid bifurcations. With the optimized parameter settings the method successfully tracked the central vessel paths in 201 of the remaining 204 bifurcations (99%) which were not part of the training set. Comparison with manually drawn segmentations shows that the average overlap between the method and observers is similar (for the inter-observer set the results were 92% vs. 87% and for the intra-observer set 94% vs. 94%). Therefore the method has potential to replace the manual procedure of lumen segmentation of the atherosclerotic bifurcation in CTA.
    Medical image analysis 12/2010; 14(6):759-69. · 3.09 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An accurate spatial relationship between 3D in-vivo carotid plaque and lumen imaging and histological cross sections is required to study the relationship between biomechanical parameters and atherosclerotic plaque components. We present and evaluate a fully three-dimensional approach for this registration problem, which accounts for deformations that occur during the processing of the specimens. By using additional imaging steps during tissue processing and semi-automated non-linear registration techniques, a 3D-reconstruction of the histology is obtained. The methodology was evaluated on five specimens obtained from patients, operated for severe atherosclerosis in the carotid bifurcation. In more than 80% of the histology slices, the quality of the semi-automated registration with computed tomography angiography (CTA) was equal to or better than the manual registration. The inter-observer variability was between one and two in-vivo CT voxels and was equal to the manual inter-observer variability. Our technique showed that the angles between the normals of the registered histology slices and the in-vivo CTA scan direction ranged 6-56 degrees , indicating that proper 3D-registration is crucial for establishing a correct spatial relation with in-vivo imaging modalities. This new 3D-reconstruction technique of atherosclerotic plaque tissue opens new avenues in the field of biomechanics as well as in the field of image processing, where it can be used for validation purposes of segmentation algorithms.
    Journal of biomechanics 05/2010; 43(11):2087-92. · 2.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Atherosclerotic carotid plaque ulceration is considered a marker of previous plaque rupture and subsequent thromboembolism. It can be accurately detected with multidetector CTA. We hypothesized that atherosclerotic plaque ulceration is associated with nonlacunar ischemic stroke rather than lacunar stroke. Prospectively, 750 consecutive patients with transient ischemic attack or ischemic stroke symptoms in the anterior cerebral circulation were evaluated for the presence of atherosclerotic plaque ulceration in the symptomatic carotid artery with multidetector CTA. Patients with stroke attributable to cardiac embolism or other specific etiologies and patients with amaurosis fugax were excluded. Ischemic strokes in the remaining 534 patients were classified as nonlacunar (n=236) or lacunar (n=298) based on clinical symptoms and multidetector CT of the brain. Ulceration was defined as extension of contrast material beyond the vascular lumen into the surrounding plaque. Plaque ulceration in the symptomatic carotid artery was more common in nonlacunar strokes (n=47; 20%) as compared to lacunar strokes (n=20; 7%; P<0.001). After adjustment for age, gender, cardiovascular risk factors, and degree of stenosis, ulcerations were independently associated with nonlacunar stroke compared to lacunar stroke (odds ratio, 2.70; 95% confidence interval, 1.43-5.09). Atherosclerotic carotid plaque ulceration is associated with nonlacunar ischemic stroke, independent of the degree of carotid stenosis. These results suggest that nonlacunar stroke and lacunar stroke are caused by different pathophysiological mechanisms.
    Stroke 04/2010; 41(6):1151-6. · 6.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The distensibility of a blood vessel is a marker of atherosclerotic disease. Manual measurement of the distensibility on CTA images is a difficult task. In this paper we describe a method to automatically determine the distensibility of the carotid artery by locally analyzing the deformation field of a nonrigid registration of a series of ECG-gated CTA images. We evaluate two variants of the method, and compare the results with manually measured distensibilities.
    Proceedings of the 2010 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, Rotterdam, The Netherlands, 14-17 April, 2010; 01/2010
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A novel method is presented for carotid artery vessel wall segmentation in computed tomography angiography (CTA) data. First the carotid lumen is semi-automatically segmented using a level set approach initialized with three seed points. Subsequently, calcium regions located within the vessel wall are automatically detected and classified using multiple features in a GentleBoost framework. Calcium regions segmentation is used to improve localization of the outer vessel wall because it is an easier task than direct outer vessel wall segmentation. In a third step, pixels outside the lumen area are classified as vessel wall or background, using the same GentleBoost framework with a different set of image features. Finally, a 2-D ellipse shape deformable model is fitted to a cost image derived from both the calcium and vessel wall classifications. The method has been validated on a dataset of 60 CTA images. The experimental results show that the accuracy of the method is comparable to the interobserver variability.
    IEEE transactions on medical imaging. 07/2009; 29(1):65-76.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to examine the volume and the composition of atherosclerotic plaque in symptomatic carotid arteries and to investigate the relationship between these plaque features and the severity of stenosis and the presence of cardiovascular risk factors. One hundred patients with cerebrovascular symptoms underwent CT angiography. We measured plaque volume (PV) and the relative contribution of plaque components (calcifications, fibrous tissue, and lipid) in the symptomatic artery. The contribution of different components was measured as the number of voxels within defined ranges of HU values (calcification >130 HU, fibrous tissue 60-130 HU, lipid core <60 HU). Fifty-seven patients had atherosclerotic plaque in the symptomatic carotid artery. The severity of stenosis and PV were moderately correlated. Age and smoking were independently related to PV. Patients with hypercholesterolemia had significantly less lipid and more calcium in their plaques than patients without hypercholesterolemia. Other cardiovascular risk factors were not significantly related to PV or plaque composition. Luminal stenosis of the carotid artery partly reflects the amount of atherosclerotic carotid disease. Plaque volume and plaque composition are associated with cardiovascular risk factors.
    European Radiology 05/2009; 19(9):2294-301. · 4.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel, slice-based, semi-automatic method for plaque segmentation and quantification in CTA of carotid arteries is introduced. The method starts with semi-automatic, levelset based, lumen segmentation initialized with three points. Pixel based GentleBoost classification is used to segment the inner and outer vessel wall region using distance from the lumen, intensity and Gaussian derivatives as features. 3D calcified regions located within the vessel wall are segmented using a similar set of features and the same classification method. Subsequently, an ellipse-shaped deformable model is fitted using the inner-outer vessel wall and calcium classification, and plaque components within the wall are characterized using HU ranges. The method is quantitatively evaluated on 5 carotid arteries. Vessel and plaque segmentation are compared to the interobserver variability. Furthermore, correlation of slice-based plaque component quantification with the ground truth values is determined. The accuracy of our method is comparable to the interobserver variability.
    Proceedings of the 2009 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, Boston, MA, USA, June 28 - July 1, 2009; 01/2009
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Atherosclerotic calcifications are present not only in the extracranial carotid bifurcation but also in the intracranial part of the internal carotid artery. We assessed the association between intracranial internal carotid artery calcifications and cardiovascular risk factors in patients with ischemic cerebrovascular disease and the association between calcifications and the presence of this disease. Patients undergoing multidetector CT (MDCT) angiography of the carotid arteries for assessment of stenosis degree were included in the study. A semiautomatic custom-made system to quantify calcifications was developed. The associations between the volume of calcifications and cardiovascular risk factors and the type of ischemic cerebrovascular symptoms were assessed with logistic regression. MDCT angiography was performed in 406 patients (age, 62 +/- 14 years; 242 men). Men had a significantly higher calcification volume (66 mm(3)) than women (33 mm(3)). Calcification volume was positively associated with age in both men and women. Smoking, hypercholesterolemia, and a history of cardiac disease were independently related to the presence of calcifications. A history of cardiac disease and ischemic cerebrovascular disease were independently related to the volume of calcifications. No association was found between calcifications and the presence or type of ischemic cerebrovascular disease in the vascular territory of the intracranial internal carotid artery. Calcifications were associated with higher age and male gender. The presence and volume of calcifications were independently associated with cardiovascular risk factors. Calcifications were not related to the presence or type of ischemic cerebrovascular disease.
    American Journal of Neuroradiology 11/2008; 30(1):177-84. · 3.17 Impact Factor