DOI: 10.1007/3-540-45468-3_94 Conference: Medical Image Computing and Computer-Assisted Intervention - MICCAI 2001, 4th International Conference, Utrecht, The Netherlands, October 14-17, 2001, Proceedings
An analysis package called QVAS (quantitative vascular analysis system) is presented for the evaluation of atherosclerotic
arterial lesions visualized in vivo by magnetic resonance imaging. QVAS permits interactive identification of vessel and lesion
boundaries, segmentation of tissue classes within the lesion, quantitative analysis of lesion features, and three dimensional
display of lesion structure. The performance of QVAS is demonstrated using images of carotid artery lesions.
"A multi-scale scanning of the entire image in order to find the most circular shape  leads to full automation but may fail when the cross-sectional shape is deformed by the pathology. A pre-segmentation of the image, based on the Markov Random Fields theory, has also been proposed for the initialization of an active contour . The initial nodes of the active contour can also be sought radially, as the maximum contrast points, starting from an interactively indicated point within the vessel lumen  . "
[Show abstract][Hide abstract] ABSTRACT: Vessel-wall measurements from multicontrast MRI provide information on plaque structure and evolution. This requires the extraction of numerous contours. In this work a contour-extraction method is proposed that uses an active contour model (NLSnake) adapted for a wide range of MR vascular images. This new method employs length normalization for the purpose of deformation computation and offers the advantages of simplified parameter tuning, fast convergence, and minimal user interaction. The model can be initialized far from the boundaries of the region to be segmented, even by only one pixel. The accuracy and reproducibility of NLSnake endoluminal contours were assessed on vascular phantom MR angiography (MRA) and high-resolution in vitro MR images of rabbit aorta. An in vivo evaluation was performed on rabbit and clinical data for both internal and external vessel-wall contours. In phantoms with 95% stenoses, NLSnake measured 94.3% +/- 3.8%, and the accuracy was even better for milder stenoses. In the images of rabbit aorta, variability between NLSnake and experts was less than interobserver variability, while the maximum intravariability of NLSnake was equal to 1.25%. In conclusion, the NLSnake technique successfully quantified the vessel lumen in multicontrast MR images using constant parameters.
Magnetic Resonance in Medicine 02/2004; 51(2):370-9. DOI:10.1002/mrm.10722 · 3.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: High-resolution MRI provides unique information about morphology of atherosclerotic carotid plaque. In this study, the accuracy and precision of measurements of carotid plaque burden and lumen narrowing were determined for in vivo black blood MRI assessment with respect to ex vivo MRI in a group of 37 atherosclerosis patients who underwent carotid endarterectomy (CEA). Three different plaque measures were compared between paired in vivo and ex vivo MR images: maximum wall area (MWA), minimum lumen area (mLA), and wall volume (WV). MWA and WV are measures of plaque burden, while mLA is a measure of lumen narrowing. The matched in vivo and ex vivo measurements showed good agreement (the correlation coefficients for in/ex vivo WV, MWA, and mLA were 0.92, 0.91, 0.90, respectively) with predictable bias. This study indicates that in vivo black blood MRI can be used to directly estimate the morphology of the plaque. Comparison of the three plaque measures showed that mLA and MWA or WV provide different information regarding the atherosclerotic lesions (the correlation coefficients between mLA and MWA or WV were less than 0.3). Black blood MRI technique is a potentially powerful clinical tool to characterize the severity of atherosclerotic plaque. It can provide accurate measurements on different aspects of the plaque, from plaque burden to lumen narrowing.
Magnetic Resonance in Medicine 07/2003; 50(1):75-82. DOI:10.1002/mrm.10503 · 3.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study evaluates the ability of MRI to quantify all major carotid atherosclerotic plaque components in vivo.
Thirty-one subjects scheduled for carotid endarterectomy were imaged with a 1.5T scanner using time-of-flight-, T1-, proton density-, and T2-weighted images. A total of 214 MR imaging locations were matched to corresponding histology sections. For MRI and histology, area measurements of the major plaque components such as lipid-rich/necrotic core (LR/NC), calcification, loose matrix, and dense (fibrous) tissue were recorded as percentages of the total wall area. Intraclass correlation coefficients (ICCs) were computed to determine intrareader and inter-reader reproducibility. MRI measurements of plaque composition were statistically equivalent to those of histology for the LR/NC (23.7 versus 20.3%; P=0.1), loose matrix (5.1 versus 6.3%; P=0.1), and dense (fibrous) tissue (66.3% versus 64%; P=0.4). Calcification differed significantly when measured as a percentage of wall area (9.4 versus 5%; P<0.001). Intrareader and inter-reader reproducibility was good to excellent for all tissue components, with ICCs ranging from 0.73 to 0.95.
MRI-based tissue quantification is accurate and reproducible. This application can be used in therapeutic clinical trials and in prospective longitudinal studies to examine carotid atherosclerotic plaque progression and regression.
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