نتایج جستجو برای: voxel model

تعداد نتایج: 2115264  

Journal: :Information processing in medical imaging : proceedings of the ... conference 2009
Hongtu Zhu Yimei Li Joseph G. Ibrahim Weili Lin Dinggang Shen

We develop a novel statistical model, called multiscale adaptive regression model (MARM), for spatial and adaptive analysis of neuroimaging data. The primary motivation and application of the proposed methodology is statistical analysis of imaging data on the two-dimensional (2D) surface or in the 3D volume for various neuroimaging studies. The existing voxel-wise approach has several major lim...

2008
Tanya Schmah Geoffrey E. Hinton Richard S. Zemel Steven L. Small Stephen C. Strother

Neuroimaging datasets often have a very large number of voxels and a very small number of training cases, which means that overfitting of models for this data can become a very serious problem. Working with a set of fMRI images from a study on stroke recovery, we consider a classification task for which logistic regression performs poorly, even when L1or L2regularized. We show that much better ...

Journal: :Magnetic resonance imaging 2012
Iain P Bruce M Muge Karaman Daniel B Rowe

The acquisition of sub-sampled data from an array of receiver coils has become a common means of reducing data acquisition time in MRI. Of the various techniques used in parallel MRI, SENSitivity Encoding (SENSE) is one of the most common, making use of a complex-valued weighted least squares estimation to unfold the aliased images. It was recently shown in Bruce et al. [Magn. Reson. Imag. 29(2...

Journal: :Comput. J. 2005
Valentin E. Brimkov Reneta P. Barneva

In this paper we investigate the advantages of using hexagonal grids in raster and volume graphics. In 2D, we present a hexagonal graphical model based on a hexagonal grid. In 3D, we introduce two honeycomb graphical models in which the voxels are hexagonal prisms, and we show that these are the only possible models under certain reasonable conditions. In the framework of the proposed models, w...

Journal: :IEEE Trans. Vis. Comput. Graph. 2003
Fakir S. Nooruddin Greg Turk

Two important tools for manipulating polygonal models are simplification and repair and we present voxel-based methods for performing both of these tasks. We describe a method for converting polygonal models to a volumetric representation in a way that handles models with holes, double walls, and intersecting parts. This allows us to perform polygon model repair simply by converting a model to ...

2001
Eduardo Solanas Jean-Philippe Thiran

An unsupervised model-based strategy for bias field correction is proposed. We assume that information (in the sense of the information theory) in the corrupted image is greater than that in the uncorrupted one. The method exploits the fact that neighboring voxels are highly correlated to correct the bias field using a linear model.

2003
Torbjørn Vik Fabrice Heitz Jean-Paul Armspach

When developing statistical models of normal brain perfusion, two questions are of crucial interest: How well does an atlas describe normality and how sensitive is it at detecting abnormalities? In this work we attempt to find partial responses to these questions by extensively experimenting with our local database of SPECT images of normal subjects, systematically synthesizing abnormalities an...

2009
Kevin Lynch Carlo Ratti Eugenio Morello

New techniques to measure 2-D and 3-D visibility over urban spaces are presented in this paper. The concept of ‘isovist’, i.e. the visible space from a vantage point, could help in providing a quantifiable basis for Kevin Lynch's urban analysis, as outlined in his book The Image of the City. We also expand on the concept of 3-D isovists and develop a new technique to calculate them on Digital E...

Journal: :NeuroImage 2005
Daniel B Rowe Brent R Logan

Due to phase imperfections, voxel time course measurements are complex valued. However, most fMRI studies measure activation using magnitude-only time courses. We show that magnitude-only analyses are equivalent to a complex fMRI activation model in which the phase is unrestricted, or allowed to dynamically change over time. This suggests that improvements to the magnitude-only model are possib...

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