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Measuring, Mapping and Modeling Brain Structure and Function
Source: SPIE Med Imag 1997;3033:104-115.
Author: Toga AW & Thompson PM
Abstract:
Presently available anatomic atlases provide useful coordinate systems such as the ubiquitous Talairach system but are sorely lacking in both spatial resolution and completeness. An appropriately sampled anatomic specimen can provide the additional detail necessary to accurately localize activation sites as well as provide other structural perspectives such as chemoarchitecture. We collected serial section postmortem anatomic data from several whole human head and brain specimens using a cryosectioning technique. Tissue imaged so that voxel resolution was 200 microns or better at full color. These high resolution datasets along with collections of MR data were placed within a common coordinate system and used to produce a probabilistic representation. This approach represents anatomy within a coordinate system as a probability. Coordinate locations are assigned a confidence limit to describe the likelihood that a given location belongs to an anatomic structure based upon the population of specimens. A variety of warping strategies are discussed to provide statistics on morphometric variability and probability. High dimensional anatomically based warps utilizing sulcal anatomy are described. These data are an important and necessary part of the comphrehensive structural and functional analyses that focus on the mapping of the human brain. INTRODUCTON: Measuring, mapping, and modeling the brain requires the ability to perceive and quantitate its anatomic and functional characteristics. The development of brain atlases is intended to provide the relationship between these characteristics and a spatially defined coordinate system. Most atlases of the human brain and, other species, are derived from one, or at best a few, individual specimens. Such atlases may take the form of anatomical references or they may represent a particular feature of the brain. The commonly used human atlases include those of Talairach and Schaltenbrand and Wahren. Variance between human brains is becoming more well understood. Accurate localization of brain structure and function in any modality is improved by correlation with higher resolution anatomic data placed within an appropriate spatial coordinate system. DEFORMABLE ATLASES: Mapping and modeling requires the severity of subtle deviations from normal brain structure and function to be measured precisely. Recent developments in mathematical approaches to brain mapping offer viable solutions to this problem retaining comprehensive information on inter-subject variations in brain architecture. Deformable atlases can be used to carry 3D maps of functional and vascular territories into the coordinate system of different patients, as well as information on different tissue types and the boundaries of cytoarchitectonic fields and their neurochemical composition. PROBABILISTIC ATLASES: Probabilistic atlasing is a research strategy whose goal is to generate anatomical templates and expert diagnostic systems which retain quantitative information on inter-subject variations in brain architecture. The recent interest in comprehensive brain mapping also stresses that the comparisons between subjects, both within and across homogeneous populations, are required to understand normal variability and genuine structural and functional differences. Initial attempts to derive average representations of neuroanatomy have underscored the power of this approach in both clinical and research settings. MEASUREMENT AND MODELING: Morphometric statistics describing subcortical structures such as; anterior commissure, caudate, putamen, globus pallidus, and thalamus as well as cortical sulcal landmarks in image data from postmortem cryosectioned anatomy and MR were relatively consistent across subjects and in general agreement with the Talairach atlas data. Mean surface area, volume, and center of mass demonstrated significantly less variability between hemispheres in comparison to intersubject variablity. CONCLUSION: In the future, rapid access to digital image archives, as well as computational tools, will be fundamental to many hypothesis-driven investigations of brain anatomy and function in health and disease. The establishment of powerful brain atlasing approaches, together with methods for guaranteeing the comparability of research findings from different laboratories, are central to the task of comprehensive brain mapping. Internet repositories of software tools, such as those for creating deformable neuroanatomic atlases, will enable the transfer of multi-subject 3D functional, vascular and histologic maps onto a single anatomic template, the mapping of local shape changes in 3D medical images in disease, and during normal or abnormal growth and development.
Source: SPIE Med Imag 1997;3033:104-115.
Author: Toga AW & Thompson PM
Abstract:
Presently available anatomic atlases provide useful coordinate systems such as the ubiquitous Talairach system but are sorely lacking in both spatial resolution and completeness. An appropriately sampled anatomic specimen can provide the additional detail necessary to accurately localize activation sites as well as provide other structural perspectives such as chemoarchitecture. We collected serial section postmortem anatomic data from several whole human head and brain specimens using a cryosectioning technique. Tissue imaged so that voxel resolution was 200 microns or better at full color. These high resolution datasets along with collections of MR data were placed within a common coordinate system and used to produce a probabilistic representation. This approach represents anatomy within a coordinate system as a probability. Coordinate locations are assigned a confidence limit to describe the likelihood that a given location belongs to an anatomic structure based upon the population of specimens. A variety of warping strategies are discussed to provide statistics on morphometric variability and probability. High dimensional anatomically based warps utilizing sulcal anatomy are described. These data are an important and necessary part of the comphrehensive structural and functional analyses that focus on the mapping of the human brain. INTRODUCTON: Measuring, mapping, and modeling the brain requires the ability to perceive and quantitate its anatomic and functional characteristics. The development of brain atlases is intended to provide the relationship between these characteristics and a spatially defined coordinate system. Most atlases of the human brain and, other species, are derived from one, or at best a few, individual specimens. Such atlases may take the form of anatomical references or they may represent a particular feature of the brain. The commonly used human atlases include those of Talairach and Schaltenbrand and Wahren. Variance between human brains is becoming more well understood. Accurate localization of brain structure and function in any modality is improved by correlation with higher resolution anatomic data placed within an appropriate spatial coordinate system. DEFORMABLE ATLASES: Mapping and modeling requires the severity of subtle deviations from normal brain structure and function to be measured precisely. Recent developments in mathematical approaches to brain mapping offer viable solutions to this problem retaining comprehensive information on inter-subject variations in brain architecture. Deformable atlases can be used to carry 3D maps of functional and vascular territories into the coordinate system of different patients, as well as information on different tissue types and the boundaries of cytoarchitectonic fields and their neurochemical composition. PROBABILISTIC ATLASES: Probabilistic atlasing is a research strategy whose goal is to generate anatomical templates and expert diagnostic systems which retain quantitative information on inter-subject variations in brain architecture. The recent interest in comprehensive brain mapping also stresses that the comparisons between subjects, both within and across homogeneous populations, are required to understand normal variability and genuine structural and functional differences. Initial attempts to derive average representations of neuroanatomy have underscored the power of this approach in both clinical and research settings. MEASUREMENT AND MODELING: Morphometric statistics describing subcortical structures such as; anterior commissure, caudate, putamen, globus pallidus, and thalamus as well as cortical sulcal landmarks in image data from postmortem cryosectioned anatomy and MR were relatively consistent across subjects and in general agreement with the Talairach atlas data. Mean surface area, volume, and center of mass demonstrated significantly less variability between hemispheres in comparison to intersubject variablity. CONCLUSION: In the future, rapid access to digital image archives, as well as computational tools, will be fundamental to many hypothesis-driven investigations of brain anatomy and function in health and disease. The establishment of powerful brain atlasing approaches, together with methods for guaranteeing the comparability of research findings from different laboratories, are central to the task of comprehensive brain mapping. Internet repositories of software tools, such as those for creating deformable neuroanatomic atlases, will enable the transfer of multi-subject 3D functional, vascular and histologic maps onto a single anatomic template, the mapping of local shape changes in 3D medical images in disease, and during normal or abnormal growth and development.