			Home About us Contact

Magnetic Resonance Imaging Techniques (magnetic + resonance_imaging_techniques)

Distribution by Scientific Domains

Medical Sciences	75%

Selected Abstracts

Estimation of relaxation time distributions in magnetic resonance imaging

THE CANADIAN JOURNAL OF STATISTICS, Issue 3 2001
Edward Susko
Abstract Magnetic resonance imaging techniques can be used to measure some biophysical properties of tissue. In this context, the T2 relaxation time is an important parameter for soft-tissue contrast. The authors develop a new technique to estimate the integral of the distribution of T2 relaxation time without imposing any constraint other than the monotonicity of the underlying cumulative relaxation time distribution. They explore the properties of the estimation and its applications for the analysis of breast tissue data. As they show, an extension of linear discriminant analysis is found to distinguish well between two classes of breast tissue. Estimation de la loi du temps de décontraction en imagerie par résonance magnétique Les techniques d'imagerie par résonance magnétique permettent de mesurer certaines propriétés biophysiques des tissus. Dans ce contexte, le temps de décontraction T2 est un paramètre important pour l'identification des tissus mous. Les auteurs proposent une nouvelle technique d'estimation de l'intégrate de la loi du temps de décontraction T2 sans imposer d'autres contraintes que la monotonicité de la fonction de répartition de la variable sous-jacente. Ils explorent les propriétés de l'estimateur et montrent son utilité dans l'analyse de tissus mammaires. Comme ils le font valoir, une généralisation de l'analyse discriminante linéaire permet de distinguer nettement entre deux types de tissus mammaires. [source]

The utility of magnetic resonance imaging in evaluating peripheral nerve disorders

MUSCLE AND NERVE, Issue 3 2002
Gerald A. Grant MD
Abstract The evaluation of peripheral nerve injuries has traditionally relied primarily on information gained from the clinical history, physical examination, and electrodiagnostic testing. Taken together, all of this clinical and diagnostic information often allows one to determine the location and severity of the underlying peripheral nerve problem. However, it may not be sufficient in diagnosing a focal entrapment neuropathy superimposed upon a more generalized peripheral neuropathy; localizing a focal lesion along a long segment of nerve which may be difficult to assess accurately with electrodiagnostic sutdies; distinguishing early between an axonotmetic grade of injury, which can recover through axonal regeneration, and a neurotmetic grade which cannot and therefore may benefit from a surgical exploration and repair procedure; and noninvasively diagnosing and determining the surgical resectability of peripheral nerve mass lesions such as tumors. The goal of this review is to illustrate how standard and evolving magnetic resonance imaging techniques can provide additional information in dealing with some of these problems. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000,000, 2002 DOI 10.1002/mus.10013 [source]

Denuded subchondral bone and knee pain in persons with knee osteoarthritis

ARTHRITIS & RHEUMATISM, Issue 12 2009
Kirsten Moisio
Objective It is unclear how articular cartilage loss contributes to pain in patients with knee osteoarthritis (OA). Full-thickness cartilage defects expose the subchondral bone plate. The relationship between denuded bone and pain has not been examined. The aim of this study was to investigate whether the percent of denuded bone is associated with moderate-to-severe knee pain or frequent knee pain and longitudinally with frequent knee pain 2 years after the baseline evaluation. Methods We studied 182 persons with knee OA (305 knees). Applying specialized magnetic resonance imaging techniques, manual segmentation was used to compute cartilage-covered and denuded bone areas for each surface. Moderate-to-severe knee pain was defined as a score of ,40 mm on a knee-specific 100-mm visual analog scale, and frequent knee pain was defined as pain on most days during the past month. Logistic regression and generalized estimating equations were used in analyses, adjusting for age, sex, body mass index, and bone marrow lesions. Results Cross-sectional analyses revealed that moderate-to-severe knee pain was associated with percent denuded bone in the medial compartment (adjusted odds ratio [OR] 3.90, 95% confidence interval [95% CI] 1.33,11.47), in the medial and patellar surfaces together, and in the lateral and patellar surfaces. Frequent knee pain was associated with percent denuded bone in the patellar surface (adjusted OR 3.11, 95% CI 1.24,7.81), in the medial and patellar surfaces, and in the lateral and patellar surfaces. Longitudinal analyses (in 168 knees without frequent knee pain at baseline) revealed that percent denuded bone in the medial and patellar surfaces was associated with frequent incident knee pain (adjusted OR 4.19, 95% CI 1.56,11.22). Conclusion These results support a relationship between subchondral bone plate exposure and prevalent and incident knee pain in patients with knee OA. [source]

The histopathology of grey matter demyelination in multiple sclerosis

ACTA NEUROLOGICA SCANDINAVICA, Issue 2009
L. Bø
Multiple sclerosis (MS) is characterized by focal demyelinating lesions in white matter (WM) and grey matter (GM) of the central nervous system. Results of studies using quantitative magnetic resonance imaging techniques indicate that GM MS pathology has a significant impact on clinical symptoms and disability in MS, and may occur partly independently of WM pathology. Subpial cerebral and cerebellar cortexes are predilection sites for demyelination in MS. Significant neuronal and axonal pathology has been detected in GM MS lesions. The pathology of MS lesions is location-dependent; there is less pronounced inflammation in GM lesion areas than in WM lesions. The presence and extent of GM lesions has recently been correlated to meningeal inflammation, and cells infected with the Epstein,Barr virus have been detected in meningeal infiltrates, suggesting a role of meningeal inflammation in cortical lesion pathogenesis. [source]