Biomedical subjects

William S Kerwin

Publications and source records attributed to William S Kerwin.

4 recordsLinked to original sources

PubMed2003

In vivo accuracy of multisequence MR imaging for identifying unstable fibrous caps in advanced human carotid plaques.

PURPOSE: To evaluate the in vivo accuracy of a multisequence MRI technique for prospectively identifying one feature of the vulnerable plaque-an unstable fibrous cap-in human carotid atherosclerosis. MATERIALS AND METHODS: The carotid arteries of 18 endarterectomy patients were preoperatively imaged in a 1.5 T scanner using a multisequence protocol that generated four contrast weightings (3D time of flight (ToF), T1, proton density (PD), and T2) at each slice location. With the use of previously published MR criteria, the images of the vessel wall were first examined for evidence of an unstable fibrous cap. The imaging findings were then correlated with the histology from the surgical specimens. RESULTS: A blinded review of the MR findings with the histologic state of the fibrous cap revealed that 1). assessing the preoperative appearance of the fibrous cap has a high test sensitivity (0.81) and specificity (0.90) for identifying an unstable cap in vivo; and 2). the availability of different contrast weightings facilitated image interpretation when intimal calcifications or flow artifacts obscured the lumen surface. CONCLUSION: Multisequence MRI can accurately characterize the in vivo state of the fibrous cap. This finding supports the use of these noninvasive techniques to prospectively identify vulnerable plaques.

Carotid Arteries↗

PubMed2003

Accuracy and uniqueness of three in vivo measurements of atherosclerotic carotid plaque morphology with black blood MRI.

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.

Aged↗

PubMed2003

Detecting objects in image sequences using rule-based control in an active contour model.

A method is presented for tracking object boundaries in sequential images using an active contour model, based on fuzzy reasoning rule-based control. Evolution of contour segments is controlled by separate processes based on whether the segment is judged to be inside, outside, or near the boundary of the object, leading to robust boundary detection.

Algorithms↗

PubMed2002

Contrast-enhanced high resolution MRI for atherosclerotic carotid artery tissue characterization.

PURPOSE: To determine if a gadolinium-based contrast agent provides additional information for characterization of human plaque tissues, particularly neovasculature. Although high-resolution magnetic resonance imaging (MRI) has been used to identify plaque constituents in advanced atherosclerosis, some constituents, such as neovascularized tissue, defy detection. MATERIALS AND METHODS: Non-contrast-enhanced carotid artery images from 18 patients scheduled for carotid endarterectomy and two normal volunteers were used to identify regions of fibrous tissue, necrotic core, or calcification, using established criteria. Then, the percent change in T1-weighted images after contrast enhancement was calculated for each region. RESULTS: There were statistically significant differences in mean intensity change between tissues, with the largest increase for fibrous tissue (79.5%) and the smallest for necrotic core (28.6%). Additionally, histological analysis showed that a subset of fibrous regions rich in plaque neovascularization could be identified using a threshold of 80% enhancement (sensitivity = 76%, specificity = 79%). CONCLUSION: The ability of contrast-enhanced MRI to identify neovascularization and potentially improve differentiation of necrotic core from fibrous tissue further establishes MRI as a viable tool for in vivo study of atherosclerotic plaque.

Analysis of Variance↗