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Voxel-based morphometry is a computational approach to neuroanatomy that measures differences in local concentrations of brain tissue, through a voxel-wise comparison of multiple brain images. [ 1 ] [ 2 ] In traditional morphometry , volume of the whole brain or its subparts is measured by drawing regions of interest (ROIs) on images from brain ...
Usually these are acquired in a regular pattern (e.g., one slice for each millimeter of depth) and usually have a regular number of image pixels in a regular pattern. This is an example of a regular volumetric grid, with each volume element, or voxel represented by a single value that is obtained by sampling the immediate area surrounding the ...
Modern 3 Tesla clinical MRI scanner.. Magnetic resonance imaging (MRI) is a medical imaging technique mostly used in radiology and nuclear medicine in order to investigate the anatomy and physiology of the body, and to detect pathologies including tumors, inflammation, neurological conditions such as stroke, disorders of muscles and joints, and abnormalities in the heart and blood vessels ...
A voxel is a three-dimensional counterpart to a pixel. It represents a value on a regular grid in a three-dimensional space . Voxels are frequently used in the visualization and analysis of medical and scientific data (e.g. geographic information systems (GIS)). [ 1 ]
Computational speed is restricted by the file sizes of 3D images, which are significantly larger than 2D images. For example, an 8-bit (1024x1024) pixel 2D image has a file size of 1 MB, while an 8-bit (1024x1024x1024) voxel 3D image has a file size of 1 GB. This can be partially offset using parallel computing. [13] [14]
where is the signal-to-noise ratio of the image (which depends on the magnetic field of the scanner, the voxel volume, and the acquisition time of the scan). For an example, setting a ‘low’ v e n c {\displaystyle v_{enc}} (below the maximum velocity expected in the scan) will allow for better visualization of slower velocities (better SNR ...
Spatial resolution of an fMRI study refers to how well it discriminates between nearby locations. It is measured by the size of voxels, as in MRI. A voxel is a three-dimensional rectangular cuboid, whose dimensions are set by the slice thickness, the area of a slice, and the grid imposed on the slice by the scanning process.
Each voxel's value is a tensor represented here by an ellipsoid. Color denotes principal orientation: red = left-right, blue=inferior-superior, green = posterior-anterior. Diffusion MRI is a structural magnetic resonance imaging modality that allows measurement of the diffusion process of molecules. Diffusion is measured by applying a gradient ...