MRI Exchange Rate Measurement Using Gradient Pulse Filtering
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Solution Overview
Problem
Current diffusion NMR methods for estimating exchange rates are either time-consuming or rely on invasive techniques, and are not applicable to all MRI instruments due to high noise levels and requirements for advanced equipment.
Innovation Solution
A method using a sequence of gradient pulses as a filter in diffusion experiments, allowing for the analysis of identical molecules based on their diffusion restriction and reducing signal attenuation, making it applicable to a wide range of MRI scanners and less affected by noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two-dimensional nuclear magnetic resonance experiments are used to examine exchange processes, then exchange rate information can be obtained, but instrument time requirements become excessively long
Solution Approach 1:
The patent extracts and isolates the specific exchange process information from the complex two-dimensional NMR data by using a filter block that selectively passes only the signal components related to molecular exchange between compartments. This extraction approach obtains exchange rate information without requiring the full two-dimensional data acquisition, dramatically reducing instrument time while maintaining measurement capability.
Solution Approach 2:
Instead of performing the complete two-dimensional NMR experiment, the patent applies partial action by using a simplified pulse sequence with a filter block that captures only the necessary exchange information. This partial approach acquires sufficient data for exchange rate determination without the excessive data collection requirements of full 2D experiments.
2Measurement precision
If diffusion NMR techniques are applied to study exchange processes, then exchange rate information can be obtained, but the signal dependence on exchange rate is very weak
Solution Approach 1:
The patent introduces a filter block as an intermediary element between the diffusion encoding block and signal detection. This filter block acts as a mediator that enhances the sensitivity to exchange processes by selectively filtering the NMR signal to emphasize exchange-related components while suppressing background signals, thereby strengthening the weak signal dependence on exchange rate.
Solution Approach 2:
The patent changes the signal processing parameters by applying a filter block with specific diffusion weighting that modifies how the NMR signal responds to exchange processes. This parameter change transforms the weak signal dependence into a more pronounced response, making exchange rate measurements more informative.
3Measurement precision
If invasive marker methods are used to observe diffusion and exchange, then exchange times can be measured, but tissue and body fluids may be affected by introduced markers
Solution Approach 1:
The patent enables the biological system to serve itself by using the intrinsic NMR properties of endogenous molecules (such as water protons) to measure exchange processes. No external markers or tracers are introduced; instead, the system's own molecular signals are exploited, completely eliminating toxicity concerns while maintaining measurement precision.
Solution Approach 2:
The patent uses naturally occurring, abundant molecules (like water) as the measurement probe instead of expensive, potentially toxic marker substances. These endogenous molecules are already present in the system and require no introduction or disposal, eliminating harmful effects while providing sufficient signal for exchange time measurement.
4Adaptability or versatility
If standard clinical MRI scanners are used for diffusion NMR, then accessibility is improved, but noise levels and equipment limitations prevent exchange rate measurement
Solution Approach 1:
The patent modifies the NMR experiment parameters by implementing a filter block with optimized diffusion weighting that adapts to the lower gradient capabilities of clinical MRI scanners. This parameter change allows exchange rate measurement on standard equipment by adjusting the sensitivity and filtering characteristics to match the available signal quality and hardware limitations.
Solution Approach 2:
The filter block serves as an intermediary that bridges the gap between limited clinical scanner capabilities and the requirement for reliable exchange rate measurement. It enhances the weak signals from clinical scanners by selectively filtering and emphasizing exchange-related components, making reliable measurements possible on standard equipment.
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
This approach enables the estimation of exchange rates with shorter experiment times, reduces noise interference, and provides a new contrast mode for MRI studies, allowing for image generation based on exchange rate differences, while being compatible with standard clinical MRI scanners.
Implementation Method 1
a filter block (first diffusion weighting block) configured to reduce at least a part of the distribution of diffusion coefficients of said object
Implementation Method 2
emitting a gradient pulse sequence towards said object, detecting a magnetic resonance signal from said object corresponding to said emitted radio frequency pulse sequence
Data Source
Figure 1~2
Figure 3(a)~3(f)
AI summary
The present invention refers to a method for magnetic resonance imaging or nuclear magnetic resonance spectroscopy comprising emitting a radio frequency and gradient pulse sequence towards an object being subjected to a magnetic field, wherein said object comprises a molecule having an atom with a nuclear spin differing from 0, encoding, detecting and acquiring a magnetic resonance signal from said object corresponding to said emitted radio frequency and gradient pulse sequence, wherein the radio frequency and gradient pulse sequence comprises a first weighting block, a mixing block with duration t m and a second weighting block, and wherein encoding, detecting and acquiring the magnetic resonance signal from said object is limited to initial decay of the signal intensity / with increasing strength of at least one of the first weighting block and the second weighting block, wherein the variation of the initial signal decay rate with t m is analysed to obtain the apparent exchange rate AXR.