The United States of America, As Represented by the Secretary, Department of Health and Human Services

The United States of America As Represented by the Department of Health

University System of Maryland

The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc.

Other

Peter J Basser

Ferenc Horkay

Dan H Benjamini

Yaniv Assaf

Wojciech Czaja

Alexander Cloninger

Ruiliang Bai

Carlo Pierpaoli

Denis LeBihan

Diego Iacono

Valery Pickalov

Michal E Komlosh

Adam Berman

Sinisa Pajevic

Alexandru V Avram

Evren Ozarslan

Magdoom Mohamed Kulam Najmudeen

Alice Maroudas

James H Mattiello

Carlo M Pierpaoli

Diffusion sensitizing gradient pulse pairs are prescribed in a manner to mitigate effects of concomitant gradient artifacts. Measured MR signals generated by applying a plurality of diffusion sensitizing gradient matrices are obtained and processed to determine a second order mean diffusion tensor and a fourth order covariance tensor. Quantities derived from these tensors are measured and mapped within an imaging volume which describe features of diffusion anisotropy and heterogeneity within each imaging voxel.

Time efficient multi-pulsed field gradient (mPFG) MRI without concomitant gradient field artifacts

Magnetic resonance methods comprise tractographically establishing a path along a structure in a specimen and finding a distribution of structure radii or cross-sectional areas along the path. Based on the distribution and the path, end-to-end functional characteristics of the structure are estimated. For example, nerve transit times or distributions of transit times can be estimated for a plurality of nervous system locations such as Brodmann areas. Comparison of estimated transit times or distributions thereof between reference values or other values from the same structure can be used to assess specimen health.

MRI tractography based transit time determination for nerve fibers

Multidimensional MRI-based methods permit identification and categorization of brain specimens to identify sub-voxel tissue components that are specific to traumatic axon injury or other lesions. Lower dimensional MR spectral data is acquired and processed to provide multidimensional MR data of higher dimensions. One or more spectral ranges are selected that define signatures for brain injury and evaluation of the multidimensional MR data in these ranges is used to locate voxels associated with brain injury. For example, partial one dimensional data sets such as T1, T2, and mean diffusion coefficient (MD) data sets can be combined to provide two dimensional data sets such as T1-T2, MD-T2, and MD-T1 data sets. Using the spectral signatures, a specimen image can be produced showing areas of lesser or greater injury.

Multidimensional MRI signature for specific detection of traumatic brain injury in vivo

A self-reinforcing composite gel includes a solvent, and a plurality of swellable crosslinked polymer particles dispersed in a crosslinked polymer matrix, wherein the crosslinked polymer matrix and the plurality of swellable crosslinked polymer particles are immersed in the solvent, wherein the swellable crosslinked polymer particles absorb more solvent at equilibrium than the matrix polymer, and wherein the plurality of swellable crosslinked polymer particles swell in the solvent and are present in an amount sufficient to maintain or increase the elastic modulus and/or load-bearing ability of the self-reinforcing composite gel, i.e., compared to that of the crosslinked matrix polymer alone, upon swelling in the solvent.

Composite gels and methods of use thereof

Multi-dimensional spectra associated with a specimen are reconstructed using lower dimensional spectra as constraints. For example, a two-dimensional spectrum associated with diffusivity and spin-lattice relaxation time is obtained using one-dimensional spectra associated with diffusivity and spin-lattice relaxation time, respectively, as constraints. Data for a full two dimensional spectrum are not acquired, leading to significantly reduced data acquisition times.

Multi-dimensional spectroscopic NMR and MRI using marginal distributions

Isotropic generalized diffusion tensor imaging methods and apparatus are configured to obtain signal attenuations using selected sets of applied magnetic field gradient directions whose averages produce mean apparent diffusion constants (mADCs) over a wide range of b-values, associated with higher order diffusion tensors (HOT). These sets are selected based on analytical descriptions of isotropic HOTs and the associated averaged signal attenuations are combined to produce mADCs, or probability density functions of intravoxel mADC distributions. Estimates of biologically-specific rotation-invariant parameters for quantifying tissue water mobilities or other tissue characteristics can be obtained such as Traces of HOTs associated with diffusion and mean t-kurtosis.

Isotropic generalized diffusion tensor MRI

Described herein are exemplary methods for estimating a nonparametric joint radius-length (R-L) distribution of an ensemble of porous elements represented generally by finite cylinders. Some described methods comprise estimating an eccentricity distribution of a group of anisotropic porous elements. For example, disclosed methods can be applied to estimate a nonparametric joint R-L distribution of injured axons in nervous tissue, muscle tissue, plant elements, or other porous materials. Employing a novel three dimensional (3-D) double pulsed-field gradient (d-PFG) magnetic resonance (MR) acquisition scheme, both the marginal radius and length distributions of a population of generally cylindrical porous elements can be obtained. The marginal radius and length distributions can then b e used to constrain and stabilize the estimate of the joint radius-length distribution. Using the marginal distributions as constraints allows the joint R-L distribution to be reconstructed from an underdetermined system (i.e., more variables than equations).

Determination of a joint probability distribution of radius and length of anisotropic pores from double pulsed field gradient MRI data

An approach is presented to recontruct image data for an object using a partial set of magnetic resonance (MR) measurements. A subset of data points in a data space representing an object are selected (e.g. through random sampling) for MR data acquisition. Partial MR data corresponding to the subset of data points is received and used for image reconstruction. The overall speed of image reconstruction can be reduced dramatically by relying on acquisition of data for the subset of data points rather than for all data points in the data space representing the object. Compressive sensing type arguments are used to fill in missing measurements, using a priori knowledge of the structure of the data. A compressed data matrix can be recovered from measurements that form a tight frame. It can be established that these measurements satisfy the restricted isometry property (RIP). The zeroth-order regularization minimization problem can then be solved, for example, using a 2D ILT approach.

Magnetic resonance 2D relaxometry reconstruction using partial data

A phantom calibration body () for calibrating diffusion MRI device () that mimics a material such as a mammalian tissue is disclosed. The phantom calibration body () includes a homogeneous aqueous solution () that contains a mixture of low molecular-weight and high molecular-weight polymers housed in a container () that is placed in the diffusion MRI device () for obtaining one or more diffusion MRI images of the phantom calibration body (). A measure of diffusivity is calculated for each of the one or more diffusion MRI images in order to calibrate the diffusion MRI device. Methods of using the phantom calibration body () to calibrate diffusion MRI device () are also disclosed.

Phantom for diffusion MRI imaging

Using pulsed-field-gradient (PFG) sequences, the sizes of the pores in ordered porous media can be estimated from the 'diffraction' pattern that the signal attenuation curves exhibit. A different diffraction pattern is observed when the experiment is extended to a larger number (N) of diffusion gradient pulse pairs. Differences in the characteristics of attenuation curves also permit distinguishing different pore shapes and distributions using the N-PFG technique. Using an even number of PFG pairs, an approximation to the average pore size can be obtained even when the sample contains pores with a broad distribution of sizes. Multi-PFG sequences can also be used to differentiate free and multi-compartment diffusion, and to estimate compartment sizes and orientations, and to distinguish microscopic and ensemble anisotropy.

Magnetic resonance specimen evaluation using multiple pulsed field gradient sequences with a wavenumber magnitude local minimum and restricted compartment estimation

Magnetic resonance methods include modeling magnetic resonance signals obtained from specimens at low and high q-values to obtain parameters and distributions of parameters associated with specimen structure and orientation. In evaluation of brain white matter specimens, diffusion within axons can be modeled based on hindered diffusion parallel to an axis of the axon and restricted diffusion perpendicular to the axis. Diffusion exterior to axons can be modeled as hindered diffusion with differing diffusivities parallel to and perpendicular to the axis. Based on extracted parameters and associated model functions, distributions of specimen properties such as intra and extra-axonal principal diffusivities and the corresponding principal directions can be estimated. Features of the axon diameter distribution can also be estimated using this approach.

Growing community of inventors

Washington, DC, United States of America

Peter J Basser