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- Santiago Aja-Fernández, Antonio Tristán-Vega, Carlos Alberola-López
- Magnetic resonance imaging
- 2009

Noise estimation is a challenging task in magnetic resonance imaging (MRI), with applications in quality assessment, filtering or diffusion tensor estimation. Main noise estimators based on the Rician model are revisited and classified in this article, and new useful methods are proposed. Additionally, all the surveyed estimators are extended to the… (More)

- Antonio Tristán-Vega, Santiago Aja-Fernández
- Medical Image Analysis
- 2010

The filtering of the Diffusion Weighted Images (DWI) prior to the estimation of the diffusion tensor or other fiber Orientation Distribution Functions (ODF) has been proved to be of paramount importance in the recent literature. More precisely, it has been evidenced that the estimation of the diffusion tensor without a previous filtering stage induces… (More)

- Antonio Tristán-Vega, Carl-Fredrik Westin, Santiago Aja-Fernández
- NeuroImage
- 2009

An estimator of the Orientation Probability Density Function (OPDF) of fiber tracts in the white matter of the brain from High Angular Resolution Diffusion data is presented. Unlike Q-Balls, which use the Funk-Radon transform to estimate the radial projection of the 3D Probability Density Function, the Jacobian of the spherical coordinates is included in… (More)

- Antonio Tristán-Vega, Carl-Fredrik Westin, Santiago Aja-Fernández
- NeuroImage
- 2010

The Funk-Radon Transform (FRT) is a powerful tool for the estimation of fiber populations with High Angular Resolution Diffusion Imaging (HARDI). It is used in Q-Ball imaging (QBI), and other HARDI techniques such as the recent Orientation Probability Density Transform (OPDT), to estimate fiber populations with very few restrictions on the diffusion model.… (More)

- Santiago Aja-Fernández, Antonio Tristán-Vega, William Scott Hoge
- Magnetic resonance in medicine
- 2011

The characterization of the distribution of noise in the magnitude MR image is a very important problem within image processing algorithms. The Rician noise assumed in single-coil acquisitions has been the keystone for signal-to-noise ratio estimation, image filtering, or diffusion tensor estimation for years. With the advent of parallel protocols such as… (More)

- Antonio Tristán-Vega, Carl-Fredrik Westin
- MICCAI
- 2011

High Angular Resolution Diffusion Imaging (HARDI) demands a higher amount of data measurements compared to Diffusion Tensor Imaging (DTI), restricting its use in practice. We propose to represent the probabilistic Orientation Distribution Function (ODF) in the frame of Spherical Wavelets (SW), where it is highly sparse. From a reduced subset of measurements… (More)

- Antonio Tristán-Vega, Santiago Aja-Fernández, Carl-Fredrik Westin
- NeuroImage
- 2012

Least Squares (LS) and its minimum variance counterpart, Weighted Least Squares (WLS), have become very popular when estimating the Diffusion Tensor (DT), to the point that they are the standard in most of the existing software for diffusion MRI. They are based on the linearization of the Stejskal-Tanner equation by means of the logarithmic compression of… (More)

- Antonio Tristán-Vega, Juan Ignacio Arribas
- IEEE Trans. Biomed. Engineering
- 2008

An end-to-end system to automate the well-known Tanner--Whitehouse (TW3) clinical procedure to estimate the skeletal age in childhood is proposed. The system comprises the detailed analysis of the two most important bones in TW3: the radius and ulna wrist bones. First, a modified version of an adaptive clustering segmentation algorithm is presented to… (More)

- Santiago Aja-Fernández, Véronique Brion, Antonio Tristán-Vega
- Magnetic resonance imaging
- 2013

Modern magnetic resonance (MR) imaging protocols based on multiple-coil acquisitions have carried on a new attention to noise and signal statistical modeling, as long as most of the existing techniques for data processing are model based. In particular, nonaccelerated multiple-coil and GeneRalized Autocalibrated Partially Parallel Acquisitions (GRAPPA) have… (More)

- Santiago Aja-Fernández, Gonzalo Vegas-Sánchez-Ferrero, Antonio Tristán-Vega
- Magnetic resonance imaging
- 2014

Parallel imaging methods allow to increase the acquisition rate via subsampled acquisitions of the k-space. SENSE and GRAPPA are the most popular reconstruction methods proposed in order to suppress the artifacts created by this subsampling. The reconstruction process carried out by both methods yields to a variance of noise value which is dependent on the… (More)