MRI tractography based transit time determination for nerve fibers
Inventors
Assignees
US Department of Health and Human Services
Publication Number
US-10996303-B2
Publication Date
2021-05-04
Expiration Date
2032-09-14
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Abstract
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.
Core Innovation
The invention presents magnetic resonance (MR) methods and apparatus for tractographically establishing a path along structures in a specimen and finding distributions of structure radii or cross-sectional areas along the path. Using this data, end-to-end functional characteristics such as nerve transit times or distributions thereof can be estimated for nervous system locations like Brodmann areas. Comparisons of these estimated transit times against reference values can assess specimen health.
The methods use diffusion tensor (DT) imaging to analyze anisotropic translational diffusion in specimens, with particular emphasis on nerve fibers and fiber bundles in brain white matter. By identifying restricted diffusion compartments and estimating geometrical characteristics like effective diameters or cross-sectional areas of nerve fibers, the invention models nerve signal propagation velocities along these paths, integrating localized geometric properties to calculate overall functional measures such as transit times or distributions.
The problem addressed is the limitation of traditional diffusion tensor imaging and tractography techniques that, while they provide structural information such as fiber orientations and fractional anisotropies, often do not yield direct functional characteristics such as transit times of nerve signals. This invention fills this gap by combining geometrical characterization along tractographically determined paths with modeling of signal propagation, thus enabling functional assessment based on MR data.
Claims Coverage
The patent includes multiple independent claims covering methods, apparatus, and computer-readable media for characterizing specimen structures via magnetic resonance imaging, focusing on pathways, geometrical characteristics, and functional values estimation.
Method for specimen structure characterization via MR tractography and geometrical analysis
Applying multiple magnetic resonance pulse sequences to a specimen to obtain MR signals and images; deriving directions of specimen structure axes from these images; establishing paths along structures based on these directions at multiple locations; calculating geometrical characteristics such as cross-sectional areas or linear dimensions along these paths; calculating contributions to specimen functional values using these geometrical characteristics; and combining these contributions to provide an estimate of a specimen functional value, specifically moments of velocity distributions for nerve fibers or related structures.
Effective diameter derivation for fiber cross sections
Determining geometrical characteristics as linear dimensions corresponding to effective diameters of fiber cross sections that represent circles with areas equal to the cross-sectional area.
Estimation based on hindered or restricted diffusion at path increments
Deriving cross-sectional areas or linear dimensions from hindered or restricted diffusion data measured along path increments of nerve fibers, fiber bundles, or brain white matter to inform functional calculations.
Signal transit time proportionality to fiber diameter
Calculating contributions to signal transit times along fiber paths as proportional to nerve fiber diameters, allowing transit time estimation based on the geometrical characterization.
Comparison and assessment of signal transit time moments
Comparing calculated signal transit time moments between different specimen locations and providing assessments based on these comparisons.
Non-transitory computer-readable medium for performing MR-based path and functional characterization
Storing computer-executable instructions that perform the described method of obtaining MR signals and images, deriving paths and geometrical characteristics, calculating functional contributions, and combining these to estimate specimen functional values as velocity distribution moments for nerve-related structures.
Apparatus combining MR imaging system and processor for path and functional estimation
Incorporating a magnetic resonance imaging system configured to acquire diffusion-weighted signals and images, coupled to a processor that determines specimen axis directions, establishes paths, estimates geometrical characteristics along these paths, estimates contributions to functional values, and combines them to provide functional value estimates as moments of velocity distributions.
Display coupled to processor for image and path visualization
Including a display coupled to the processing system to visualize the established paths, specimen, and optionally path increments.
Path establishment using principal diffusion axis
Configuring the processor to establish paths based on at least one principal diffusion axis associated with restricted compartments.
Method to arrange signal transit times as a transit time matrix indicating unconnected locations
Establishing multiple paths, calculating cross-sectional geometries and functional values such as signal transit times along these paths, and organizing the transit times into a matrix where unconnected specimen locations are indicated by blank entries.
Method for higher order moments of signal transit times arranged as a transit time matrix
Calculating and providing higher order moments of signal transit times along paths and arranging these in a transit time matrix.
The independent claims collectively address procedures and systems that combine diffusion tensor imaging-derived paths, geometrical compartment characterization based on restricted diffusion, and the calculation of associated functional values such as transit times or their moments. The claims cover methods, computer-readable media, and apparatus with display capabilities, emphasizing nerve fibers and brain white matter as specimens of interest.
Stated Advantages
The technology allows estimation of nerve signal transit times and their distributions based on magnetic resonance imaging data combined with tractography and geometrical characterization.
It enables assessment of specimen health by comparing estimated transit times against reference values, supporting diagnosis and evaluation of neurological conditions.
The system can evaluate multiple pathways and provide transit time matrices linking nervous system locations such as Brodmann areas.
Documented Applications
Assessment of brain white matter and nerve fiber bundles for diagnoses such as stroke, multiple sclerosis, Alzheimer's disease, Huntington's chorea, and neurodegeneration including axon demyelination.
Evaluation of treatment efficacy, including cancer treatment response and drug screening.
Neonatal screening and food processing.
Analysis of muscle fibers and other fibrous tissues.
Clinical and industrial evaluations involving fibrous anisotropic specimens exhibiting hindered and restricted diffusion.
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