NMR Gradient Field Measurement via Diffusion Effect
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Solution Overview
Problem
Accurately measuring the gradient field in NMR systems using single-sided magnets is challenging due to large and non-uniform gradient fields, requiring time-consuming and inaccurate methods.
Innovation Solution
A method based on the diffusion effect, acquiring and processing echo signals using a diffusion-weighted sequence, eliminating the need for dedicated magnetic field detection devices, and calculating the gradient field using a fitting function with known ADC and T2 values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic field measuring device is used to measure the gradient field, then the measurement can be performed, but the measurement is time-consuming and extremely inaccurate
Solution Approach 1:
The patent replaces the mechanical magnetic field measuring device with an NMR-based measurement method. By using the diffusion effect of water molecules in the sample to sense the gradient field strength, the system substitutes direct mechanical measurement with indirect NMR signal-based measurement, achieving both speed and accuracy improvements
Solution Approach 2:
The patent introduces water molecules as an intermediary sensing medium. The water molecules diffuse in response to the gradient field, and their diffusion characteristics (measured via NMR signal attenuation) serve as an indirect indicator of gradient field strength, enabling accurate and rapid measurement without direct probe contact
2Ease of manufacture
If a single-sided magnet is used in the NMR system, then the system is low-cost and easy to manufacture, but the gradient field is large and non-uniform making measurement difficult
Solution Approach 1:
The patent enables the NMR system to measure its own gradient field characteristics using its existing NMR functionality. By employing diffusion-weighted NMR sequences and analyzing signal attenuation in the echo signal, the system self-diagnoses its gradient field properties without requiring external measurement equipment, turning the measurement challenge into a capability demonstration
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 method allows for fast, accurate, and convenient gradient field measurement within the NMR system, improving installation and service efficiency without requiring special tools.
Implementation Method 1
Molecules in matter all have a certain diffusion motion with a random direction, which is called thermal motion or Brownian motion of molecules. After the NMR signal is excited, the diffusion motion of water molecules in the direction of the gradient field will cause the attenuation of the NMR signal.
Implementation Method 2
Molecules in matter all have a certain diffusion motion with a random direction, which is called thermal motion or Brownian motion of molecules.
Implementation Method 3
Nuclear magnetic resonance (NMR) technology utilizes the NMR phenomenon of hydrogen protons to image or detect the composition and structure of a material. When the human body is placed in an external magnetic field, these small magnets rearrange according to the magnetic field lines of the external magnetic field. If the nuclei are excited by using radio frequency (RF) pulses of a specific frequency, the spins of the nuclei (small magnets) are deflected, and resonance occurs, which is the NMR phenomenon.
Data Source
AI summary
A method for measuring a gradient field of a nuclear magnetic resonance (NMR) system based on a diffusion effect uses a non-uniform field magnet, an NMR spectrometer, a radio frequency (RF) power amplifier, an RF coil, and a standard quantitative phantom with known apparent diffusion coefficient (ADC) and time constant for decay of transverse magnetization after RF-pulse (T2). A plurality of sets of signals are acquired by an NMR sequence with different diffusion-sensitive gradient durations or different echo spacings and the magnitude of the gradient field is calculated by fitting based on the plurality of sets of signals. The method does not require an additional dedicated magnetic field detection device, has a short measurement time, is easy to use with the NMR system, and is convenient to complete gradient field measurement at the installation site, thereby improving the installation and service efficiency of the NMR system.