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Molinari F.,Polytechnic University of Turin | Meiburger K.M.,Polytechnic University of Turin | Saba L.,A.U.O. Cagliari | Rajendra Acharya U.,Ngee Ann Polytechnic | And 5 more authors.
Ultrasonics | Year: 2012

Accurate intima-media thickness (IMT) measurement of the carotid artery from minimal plaque ultrasound images is a relevant clinical need, since IMT increase is related to the progression of atherosclerosis. In this paper, we describe a novel dual snake-based model for the high-performance carotid IMT measurement, called Carotid Measurement Using Dual Snakes (CMUDS). Snakes (which are deformable contours) adapt to the lumen-intima (LI) and media-adventitia (MA) interfaces, thus enabling the IMT computation as distance between the LI and MA snakes. However, traditional snakes might be unable to maintain a correct distance and in some spatial location along the artery, it might even collapse between them or diverge. The technical improvement of this work is the definition of a dual snake-based constrained system, which prevents the LI and MA snakes from collapsing or bleeding, thus optimizing the IMT estimation. The CMUDS system consists of two parametric models automatically initialized using the far adventitia border which we automatically traced by using a previously developed multi-resolution approach. The dual snakes evolve simultaneously and are constrained by the distances between them, ensuring the regularization of LI/MA topology. We benchmarked our automated CMUDS with the previous conventional semi-automated snake system called Carotid Measurement Using Single Snake (CMUSS). Two independent readers manually traced the LIMA boundaries of a multi-institutional, multi-ethnic, and multi-scanner database of 665 CCA longitudinal 2D images. We evaluated our system performance by comparing it with the gold standard as traced by clinical readers. CMUDS and CMUSS correctly processed 100% of the 665 images. Comparing the performance with respect to the two readers, our automatically measured IMT was on average very close to that of the two readers (IMT measurement biases for CMUSS was equal to -0.011 ± 0.329 mm and -0.045 ± 0.317 mm, respectively, while for CMUDS, it was 0.030 ± 0.284 mm and -0.004 ± 0.273 mm, respectively). The Figure-of-Merit of the system was 98.5% and 94.4% for CMUSS, while 96.0% and 99.6% for CMUDS, respectively. Results showed that the dual-snake system CMUDS reduced the IMT measurement error accuracy (Wilcoxon, p < 0.02) and the IMT error variability (Fisher, p < 3 × 10 -2). We propose the CMUDS technique for use in large multi-centric studies, where the need for a standard, accurate, and automated IMT measurement technique is required. © 2012 Elsevier B.V. All rights reserved.

Saba L.,Azienda Ospedaliero Universitaria | Raz E.,New York University | Bassareo P.P.,Azienda Ospedaliero Universitaria | Di Martino M.,University of Rome La Sapienza | And 6 more authors.
Journal of Stroke and Cerebrovascular Diseases | Year: 2015

Purpose Cerebral microbleeds (CMBs) are small dot-like lesions appearing as hyposignals on gradient echo (GRE) T2∗ magnetic resonance (MR) sequences, whereas the leukoaraiosis (LA) indicates the presence of patchy areas of hypersignal on fluid-attenuated inversion recovery (FLAIR) MR sequences in the periventricular white matter. The purpose of this work was to evaluate the association between LA and CMBs. Material and Methods Eighty-five consecutive (men 55; median age 64 years) patients were retrospectively analyzed using a 1.5 T system; CMBs were studied using a T2∗-weighted GRE sequence and classified as absent (grade 1), mild (grade 2; total number of microbleeds, 1-2), moderate (grade 3; total number of microbleeds, 3-10), and severe (grade 4; total number of microbleeds, >10). LA was assessed with FLAIR MR sequences and was graded based on the European Task Force on Age-Related White Matter Changes as follows: 1 (no lesions), 2 (focal lesions > 5 mm), 3 (early confluent lesions), and 4 (diffuse involvement of an entire brain region). Results We considered 170 cerebral hemispheres. The prevalence of CMBs was 24.7% (42 of 170), whereas the prevalence of LA was 27.1% (46 of 170). A statistically significant correlation was observed between LA and CMBs (correlation rho =.495, P value =.001). Multiple logistic regression analysis showed an association between CMBs and cerebrovascular symptoms (P =.0023). Conclusion Results of this study suggest an association between CMBs and LA. Moreover, we found that LA is associated with the presence of cerebrovascular symptoms. © 2015 National Stroke Association.

Saba L.,Azienda Ospedaliero Universitaria | Gao H.,University of Strathclyde | Raz E.,New York University | Sree S.V.,CA Technologies | And 8 more authors.
Journal of Magnetic Resonance Imaging | Year: 2014

Purpose To develop a semiautomatic method based on level set method (LSM) for carotid arterial wall thickness (CAWT) measurement. Materials and Methods Magnetic resonance imaging (MRI) of diseased carotid arteries was acquired from 10 patients. Ground truth (GT) data for arterial wall segmentation was collected from three experienced vascular clinicians the semiautomatic variational LSM was employed to segment lumen and arterial wall outer boundaries on 102 MR images. Two computer-based measurements, arterial wall thickness (WT) and arterial wall area (AWA), were computed and compared with GT. Linear regression, Bland-Altman, and bias correlation analysis on WT and AWA were applied for evaluating the performance of the semiautomatic method. Results Arterial wall thickness measured by radial distance measure (RDM) and polyline distance measure (PDM) correlated well between GT and variational LSM (r=0.83 for RDM and r=0.64 for PDM, P<0.05) the absolute arterial wall area bias between LSM and three observers is less than 10%, suggesting LSM can segment arterial wall well compared with manual tracings the Jaccard Similarity (Js) analysis showed a good agreement for the segmentation results between proposed method and GT (Js 0.71±0.08), the mean curve distance for lumen boundary is 0.34±0.2 mm between the proposed method and GT, and 0.47±0.2 mm for outer wall boundary. Conclusion The proposed LSM can generate reasonably accurate lumen and outer wall boundaries compared to manual segmentation, and can work similar to a human reader. However, it tends to overestimate CAWT and AWA compared to the manual segmentation for arterial wall with small area. Copyright © 2013 Wiley Periodicals, Inc.

Molinari F.,Polytechnic University of Turin | Meiburger K.M.,Polytechnic University of Turin | Saba L.,University of Cagliari | Zeng G.,Mayo Medical School | And 5 more authors.
Journal of Ultrasound in Medicine | Year: 2012

Automated computer-aided detection systems for measurement of the carotid intimamedia thickness (IMT) are becoming popular. These systems yield lumen-intima (LI) and media-adventitia (MA) borders. In this work, we developed and validated a novel and patented completely automated IMT measurement system called carotid measurement using dual snakes (CMUDS): a class of AtheroEdge system (Global Biomedical Technologies, Inc, Roseville, CA). CMUDS is modeled as a dual parametric system corresponding to LI and MA borders with initialization from the far adventitia layer. The novelty of CMUDS is the first-order absolute moment-based external energy, which provides stable deformation. The dual snakes evolve simultaneously and are forced to maintain a regularized distance to prevent collapsing or bleeding. Two independent readers manually traced the LI/MA boundaries of a multi-institutional, multiethnic, and multi-scanner database of 665 longitudinal images for performance evaluation. CMUDS was also benchmarked against a previously developed automated technique. CMUDS correctly processed 660 images (99.2% success). The differences between the CMUDS and two manual IMT measurements (mean ± SD) were 0.013 ± 0.216 and -0.021 ± 0.197 mm, respectively. The corresponding figures of merit for CMUDS compared to reader tracings were 98.4% and 97.5%. Compared to the previous technique (IMT differences, 0.022 ± 0.276 and -0.012 ± 0.266 mm), CMUDS improved accuracy (Wilcoxon P < 0.009) and variability (Fisher P > 10 -8). Among different resolution images from original equipment manufacturer ultrasound scanners, CMUDS performed best with high-resolution images corresponding to 0.0789 mm/pixel. Accuracy in IMT measurement with the proposed automated CMUDS technique makes this system adaptable to large multi-center studies, in which such an IMT measurement system would be very useful tool. © 2012 by the American Institute of Ultrasound in Medicine.

Pedro L.M.,University of Lisbon | Sanches J.M.,University of Lisbon | Seabra J.,University of Lisbon | Suri J.S.,AtheroPoint LLC | And 2 more authors.
Echocardiography | Year: 2014

Active carotid plaques are associated with atheroembolism and neurological events; its identification is crucial for stroke prevention. High-definition ultrasound (HDU) can be used to recognize plaque structure in carotid bifurcation stenosis associated with plaque vulnerability and occurrence of brain ischemic events. A new computer-assisted HDU method to study the echomorphology of the carotid plaque and to determine a risk score for developing appropriate symptoms is proposed in this study. Plaque echomorphology characteristics such as presence of ulceration at the plaque surface, juxta-luminal location of echolucent areas, echoheterogeneity were obtained from B-mode ultrasound scans using several image processing algorithms and were combined with measurement of severity of stenosis to obtain a clinical score - enhanced activity index (EAI) - which was correlated with the presence or absence of ipsilateral appropriate ischemic symptoms. An optimal cutoff value of EAI was determined to obtain the best separation between symptomatic (active) from asymptomatic (inactive) plaques and its diagnostic yield was compared to other 2 reference methods by means of receiver-operating characteristic (ROC) analysis. Classification performance was evaluated by leave-one-patient-out cross-validation applied to a cohort of 146 carotid plaques from 99 patients. The proposed method was benchmarked against (a) degree of stenosis criteria and (b) earlier proposed activity index (AI) and demonstrated that EAI yielded the highest accuracy up to an accuracy of 77% to predict asymptomatic plaques that developed symptoms in a prospective cross-sectional study. Enhanced activity index is a noninvasive, easy to obtain parameter, which provided accurate estimation of neurological risk of carotid plaques. © 2013, Wiley Periodicals, Inc.

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