Voxel Dissection for Tissue-Specific Metabolite Quantification
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Solution Overview
Problem
Conventional magnetic resonance spectroscopy (MRS) techniques fail to segment or compartmentalize tissues within a single voxel, making it impossible to determine metabolite concentrations for specific tissue types, which can lead to masking of abnormal tissue contributions by healthy tissue, complicating diagnoses and treatments.
Innovation Solution
A method and apparatus that use a phased array coil architecture and advanced signal processing to determine metabolite concentrations for specific tissue types within a single voxel, independent of the voxel's location relative to the coils, by segmenting the voxel into compartments and applying coil-specific weighting factors to isolate metabolite contributions from different tissues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single voxel MRS generates a spectrum from all metabolites in the voxel, then the overall spectrum is obtained, but it is not possible to ascertain what tissue is contributing to the overall spectrum and metabolite contribution from one tissue may mask or hide the metabolite contribution from another tissue
Solution Approach 1:
The patent segments the single voxel into multiple tissue-specific compartments (white matter, gray matter, CSF) by integrating MRS data with MRI-based tissue segmentation. This allows separate metabolite concentration measurements for each tissue type within the voxel, preventing masking effects and enabling tissue-specific diagnostic information.
2Productivity
If phased array coil architecture is used to reduce scan time, then the number of phase encoding steps is reduced, but metabolite signals are amplified based on coil proximity to the voxel, making signals spatially inhomogeneous
Solution Approach 1:
The patent applies local quality by determining coil-specific weighting factors that account for the spatially inhomogeneous B1 fields of individual coils. These weighting factors are used to correct metabolite signals from different coils, ensuring uniform and accurate metabolite concentration measurements regardless of voxel location relative to the coil array.
3Device complexity
If a voxel is defined as a cubic region of interest, then the voxel structure is simple, but tissue types rarely have rectangular or cubic shapes so a single voxel contains multiple tissue types
Solution Approach 1:
The patent segments the cubic voxel into multiple tissue-specific sub-compartments using MRI-based tissue segmentation techniques. This allows the simple cubic voxel structure to be maintained while internally dividing it into white matter, gray matter, and CSF regions, enabling tissue-type specific metabolite measurements without changing the external voxel geometry.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate assignment of metabolite concentrations to specific tissue types within a voxel, providing independent measurements that are not influenced by the voxel's proximity to the coils, thereby improving diagnostic accuracy and differentiation between normal and abnormal tissues.
Implementation Method 1
the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Implementation Method 2
the net aligned moment, or 'longitudinal magnetization', MZ, may be rotated, or 'tipped', into the x-y plane to produce a net transverse magnetic moment Mt
Implementation Method 3
A signal is emitted by the excited spins after the excitation signal B1 is terminated and this signal may be received and processed to form an image
Implementation Method 4
magnetic field gradients (Gx, Gy, and Gz) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used
Implementation Method 5
atomic nuclei are surrounded by a cloud of electrons which slightly shield the nucleus from any external magnetic field. As the structure of the electron cloud is specific to an individual molecule or compound, the magnitude of this screening effect is then also a characteristic of the chemical environment of individual nuclei
Data Source
AI summary
An MRI apparatus is presented that includes a computer programmed to sample a single volume element (voxel) for MR spectroscopy and automatically determine respective metabolite concentrations for multiple compartment contained in the single voxel. The invention is effective in assigning metabolite concentrations to specific tissue types on a per-voxel basis for a VOI. Moreover, the invention is effective in providing metabolite concentrations for a voxel independent of that voxel's vicinity relative to the coils of the phased array. The present invention provides an effective tool in assigning metabolite concentrations from mixed pathological and normal tissues.