Uncertainty about the pathogenic linkage between subcortical white matter lesions, leukoaraiosis, and cortical atrophy may be in part due to the lack of in vivo methodology to study the anatomical ...basis for this relationship. Proposed is a framework to which one may assess the spatial basis for lesion-associated cortical changes. Several image-processing algorithms were adapted or modified into an integrated pipeline for assessing the relevance of lesion location on changes to cortical thickness. Over 1000 MRI datasets of elderly subjects from the Japanese Human Brain Project were processed and analyzed. The results demonstrate that (i) there is a correlation between the extent of white matter lesions and overall cortical thickness, and (ii) that downstream cortical atrophy depends on the location of lesions from afferent white matter fibre tracts. Furthermore, the data reveals that the association fibre networks are most vulnerable to cortical atrophy as a result of lesions to white matter pathways.
L'incertitude entourant le lien pathogénique entre les lésions subcorticales de la substance blanche, la leucoaraiose et l'atrophie corticale pourrait être le résultat de l'absence de méthodologie in vivo pour étudier la base anatomique de cette relation. Un cadre est proposé afin d'évaluer les changements corticaux associés aux lésions et causés par des perturbations anatomiques des voies de la substance blanche. Plusieurs algorithmes de traitement d'image ont été adaptés ou modifiés dans le cadre proposé afin d'évaluer l'importance de la localisation des lésions par rapport aux changements corticaux. Les résultats de l'analyse statistique montrent que la perte d'intégrité des faisceaux de fibres causée par des lésions se traduisent par une atrophie du tissu cortical innervé. Il a également été démontré que les changements dans le cortex cérébral causés par les lésions correspondait aux connexions anatomiques sous-jacentes.
To provide information related to atypical language activations (right or bilateral) in positron emission tomography in patients with left clear-cut hippocampal sclerosis.
Twelve right-handed ...patients who had been operated on left-sided hippocampal sclerosis and 12 right-handed normal subjects were included and the synonym generation task was used for evaluation of language lateralization.
Atypical language activations were frequently found in the patients compared to the controls. A total of 3 (25%) subjects in the controls showed atypical activations: 2 bilateral with right and 1 bilateral with left-sided activations. There were no clear right-sided Broca activations in the control group but almost 25% of the patients showed clear right-sided Broca activations. In the patients the incidence of atypical language activations was 91.6% (11 patients).
From the present study, it is clear that functional reorganization of the language-related neuronal network is modified in patients with left hippocampal sclerosis. Although the lesion is far from the primary language-related areas, atypical language lateralization is common in these patients and this should be considered in preoperative period.
Uncertainty about the pathogenic linkage between subcortical white matter lesions, leukoaraiosis, and cortical atrophy may be in part due to the lack of in vivo methodology to study the anatomical ...basis for this relationship. Proposed is a framework to which one may assess the spatial basis for lesion-associated cortical changes. Several image-processing algorithms were adapted or modified into an integrated pipeline for assessing the relevance of lesion location on changes to cortical thickness. Over 1000 MRI datasets of elderly subjects from the Japanese Human Brain Project were processed and analyzed. The results demonstrate that (i) there is a correlation between the extent of white matter lesions and overall cortical thickness, and (ii) that downstream cortical atrophy depends on the location of lesions from afferent white matter fibre tracts. Furthermore, the data reveals that the association fibre networks are most vulnerable to cortical atrophy as a result of lesions to white matter pathways.
Studies that seek to predict the brain microstructure based on MRI require precise alignment of processed brain histology slices to the corresponding 3D MRI data. However, achieving such alignment is ...a challenging problem, due to tissue distortions and the different contrasts seen in MRI and the processed tissue. Here we present a pipeline for aligning a histology volume to the MRI data of the tissue and to a stereotaxic brain atlas. To this end, we segment the volume of the brain from ex-vivo MRI data, align the MRI data obtained in the native space to an MRI stereotaxic template and create a 3D printed model (a mold or cradle) that precisely fits the brain. The pipeline then makes it possible to create grooves in the 3D model, for guiding blades for cutting slabs of tissue. Placing the brain in the brain-specific 3D printed model aligns the tissue to the MRI data by default. Aligning the MRI data to an MRI stereotaxic template makes it possible to section histology slices parallel to the standard stereotaxic axes of the atlas. This facilitates comparisons to other MRI contrasts and to images of processed tissue aligned to the standard space, while maintaining the high-resolution of the tissue images along the standard stereotaxic plane. Guiding the positioning of the grooves according to species-specific anatomical information from the co-registered atlas facilitates region-specific histology. The pipeline we introduce can be used to create brain-specific sectioning models for a variety of species, including humans, primates, and rodents. To demonstrate the generalizability of the pipeline across species, we show models generated for macaques and rats.
Thesis (M.Eng.).
Written for the Dept. of Biomedical Engineering & Montreal Neurological Institute. Title from title page of PDF (viewed 2008.05/13). Includes bibliographical references.
ABSTRACT
Linear measurements have many limitations. The aim of this study is to compare manual and semiautomated volumetric measurements of pituitary adenomas. Magnetic resonance imaging (MRI) scans ...of 38 patients with pituitary adenomas were analyzed. Preoperative MRI was acquired on a 1.5 T. MRI volumes of the pituitary adenomas were obtained by two methods: manual (MA) and semiautomated (SA). The concurrent validity for SA and MA methods on 38 patients in the form of correlation coefficient was 0.97 (P < 0.0001). The intraobserver and the interobserver correlation coefficients for SA volumes were both 0.98, as for the intraobserver MA volumes were 0.98. Although the results of both methods are comparable, analysis of volumetric measurements by SA method is more time-efficient than MA segmentation. Precision in volumetric measurement techniques is likely to increase reliability of posttherapeutic monitoring of pituitary adenomas.
Objective:
A key component of clinical decision making is tumor size and tumor growth over time. Conventionally, tumor size is measured linearly in one or more axis. Yet linear diameter measurements ...have many limitations (tumors are not perfect spheres). The aim of this study is to compare manual and semiautomated volumetric measurements of pituitary adenomas.
Methodology:
Twenty-six patients with pituitary adenomas were retrospectively reviewed. Preoperative T1-Gadolinium-enhanced (T1-Gd) MRI with 1.0-mm isotropic resolution was acquired on a 1.5 T for all patients. The MRI voxel-based volumes of the pituitary adenomas were obtained by two methods: manual and semiautomated segmentation. In the first method, each T1-Gd MRI was manually segmented by trained technicians using labeling and image intensity thresholding to segment tumoral tissue. In the second method, lesion tissue was identified using a semiautomated segmentation procedure, based on a user-guided level set algorithm. In both methods, the segmented lesion volumes were measured in cubic centimeters.
Result:
There were two groups in this study: manual volumes (group 1) and semiautomated volumes (group 2). Mean volume in group 1 was 9.149 cm
3
(range, 0.78–36.2 cm
3
), whereas in group 2 it was 8.59 cm
3
(range, 0.554–33.469 cm
3
). Time used to do a single manual measurement was 10 minutes, and the time spent to do a single semiautomated volumetric measurement was 5 minutes.
Conclusion:
Because most pituitary lesions are not perfectly spherical, volumetric measurements should be preferred over linear measurements. Although the results of both methods are comparable, analysis of volumetric measurements by the semiautomated method was more accurate and more time-efficient than with manual segmentation. Precision and efficiency in volumetric measurement techniques are likely to render post-therapeutic monitoring of pituitary adenomas more reliable.
I think the current confrontation is the wrong way to deal with the problem. The question is what will the natives do with the lobsters they catch. If they are holding a tribal lobsterfest to make up ...for the time when they were not allowed to fish I don't think it is any of our business to interfere with a jolly tribal get- together.
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