MRI tractography based transit time determination for nerve fibers
Inventors
Assignees
US Department of Health and Human Services
Publication Number
US-12345788-B2
Publication Date
2025-07-01
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 provides magnetic resonance (MR) methods and apparatus for estimating nerve signal transit time distributions by tractographically establishing a path along a specimen structure and finding a distribution of structure radii or cross-sectional areas along the path. Based on this distribution and the path, end-to-end functional characteristics of the structure such as nerve transit times or transit time distributions can be estimated for various nervous system locations, including Brodmann areas.
The problem addressed is that conventional diffusion tensor imaging (DTI) and tractography methods can provide structural information about anisotropic specimens like nerve fibers but often lack capability to determine functional properties such as nerve signal propagation times. Existing methods typically do not directly estimate specimen functions related to restricted diffusion, cross-sectional fiber dimensions, and their influence on nerve conduction speed. There is a need for techniques that integrate tractography with diffusion-weighted MR data to estimate functional parameters like transit times by considering fiber geometry along nerve pathways.
The disclosed technology solves this by combining diffusion tensor principal axis direction-based path determination with estimation of restricted diffusion compartment geometrical characteristics (e.g., cross-sectional areas or effective diameters) along the path, acquired from diffusion-weighted MR signals at multiple diffusion-weighted field strengths and directions. By integrating these dimensions with known or modeled relationships (e.g., conduction velocity proportional to fiber diameter), nerve signal transit times and distributions are estimated along nerve fiber bundles. These functional estimates can be compared to reference or previously obtained values to assess specimen health or abnormalities.
Claims Coverage
The claims include two independent claims: a method of evaluating MR images of nervous system specimens and a magnetic resonance apparatus configured to perform diffusion-weighted imaging and functional parameter estimation. Each claim features inventive aspects related to path establishment, diffusion-based radius distributions, and transit time calculations.
Establishing nerve pathways and transit time moments from diffusion-weighted MR images
Obtaining directions of a specimen structure axis based on MR images acquired by multiple pulse sequences; establishing pathways corresponding to nerve pathways between nervous system locations using these directions; calculating a distribution of radii of the specimen structure along these pathways; calculating transit time moments between locations based on the paths and radii distributions; arranging these moments as a matrix; comparing the transit time moments to reference values retrieved from a database; reporting specimen assessment based on the comparison.
Calculating transit time moments by summation of contributions along pathways
Calculating respective radii at multiple locations along established pathways; computing contributions to the transit time moments at these locations based on radii; combining contributions along respective pathways to obtain overall transit time moments, including moments of various orders.
Diffusion-based pathway and structural parameter determination in MR apparatus
An MR system applying diffusion-weighted pulse sequences in vivo; receiving MR signals; calculating diffusion tensors and directions from the MR images; establishing pathways between nervous system locations based on principal diffusion axes; calculating cross-sectional parameters from images; calculating transit time moments from paths and cross-sectional parameters; arranging transit time moments as a matrix for evaluation.
Using restricted and hindered diffusion data to determine cross-sectional parameters and pathways
Basing pathways and cross-sectional parameter calculations on at least one of restricted diffusion and hindered diffusion; utilizing principal diffusion axes associated with restricted or hindered diffusion compartments to guide pathway establishment and parameter estimation.
The inventive features collectively cover methods and apparatus for using diffusion-weighted MR imaging to establish nerve pathways, extract distributions of fiber cross-sectional dimensions along these paths based on restricted and hindered diffusion analysis, and compute transit time moments for nervous system assessment arranged in matrices compared against reference values.
Stated Advantages
Enables estimation of nerve signal transit times and distributions along fiber pathways noninvasively using MR data.
Provides a method to assess specimen health or abnormalities through comparison of functional transit time parameters to reference values.
Integrates structural information from diffusion tensor imaging with functional assessments related to restricted diffusion compartments.
Allows in vivo evaluation of nervous system structures such as nerve fibers, fiber bundles, and brain white matter with functional characteristics.
Documented Applications
In vivo nervous system assessment including identification of nerve pathways between nervous system locations such as Brodmann areas and estimation of transit time moments along these pathways.
Diagnostic evaluation of brain white matter and neural fibers for neurodegenerative diseases like multiple sclerosis, stroke, Alzheimer's disease, and Huntington's chorea.
Evaluation of specimen health or abnormalities by comparison of estimated transit times with reference or normative data.
Assessment and monitoring of treatment efficacy such as drug response and cancer treatments based on changes in transit time estimations from MR data.
Neonatal screening, drug screening, and clinical and industrial applications involving anisotropic specimen evaluation.
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