NMR Spin-Echo Amplitude Calibration via Echo-Shape Factor
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Solution Overview
Problem
NMR data processing underestimates spin echo amplitudes due to unknown magnetic field gradients within or across samples, leading to inaccurate fluid content estimation in various applications.
Innovation Solution
Calculating an echo-shape calibration factor by comparing the peak amplitude of recorded NMR spin or gradient echoes to their time-windowed averages, and applying this factor to correct for distortions caused by magnetic field gradients, thereby improving amplitude estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed time-domain averaging window is used to estimate spin echo amplitude, then the measurement process is simple and fast, but the amplitude estimation becomes inaccurate when echo shape varies due to magnetic field gradients
Solution Approach 1:
The patent applies preliminary action by performing a calibration measurement before the actual sample measurement. During calibration, the echo shape under known conditions (typically in water or a reference medium) is measured and stored. This pre-acquired echo shape information is then used to correct the amplitude estimation in subsequent sample measurements, eliminating the need for complex real-time shape analysis without sacrificing accuracy.
Solution Approach 2:
The patent introduces an intermediary element - the echo shape calibration factor - that mediates between the raw amplitude measurement and the corrected amplitude value. This calibration factor, derived from reference measurements, acts as a correction coefficient that accounts for system-specific echo shape characteristics, allowing simple averaging to yield accurate results when applied to the calibrated data.
2Measurement precision
If magnetic field gradients are present in the sample, then the echo shape becomes sharper and narrower, but the fixed averaging window significantly underestimates the peak echo amplitude
Solution Approach 1:
The patent uses copying by measuring and storing the echo shape from a reference sample (typically water) that replicates the measurement conditions but has known, stable properties. This reference echo shape serves as a template or copy that represents the system's response characteristics. The stored reference echo shape is then used to correct measurements of actual samples, transferring the calibration information from the reference to the unknown sample.
3Reliability
If the static magnetic field exhibits larger gradients across the sample, then the echo shape becomes narrower with rapid dephasing, but the fixed length averaging window captures less of the echo signal
Solution Approach 1:
The patent applies parameter changes by using the calibration process to determine an optimized averaging window length specific to the measurement conditions. Instead of using a fixed universal window length, the system adjusts the window length parameter based on the echo shape characteristics observed during calibration. This allows the measurement process to adapt to different gradient conditions while maintaining simple averaging as the core measurement mechanism.
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 effectively corrects for underestimation or overestimation of spin or gradient echo amplitudes, providing more accurate estimates of spin density and fluid content in samples with varying magnetic field conditions.
Implementation Method 1
NMR spin or gradient echo measurements are performed on a sample of interest
Implementation Method 2
The time domain shape of a spin echo may be controlled by the distribution of static magnetic field gradients across the spin-density volume of the sample under investigation
Data Source
AI summary
Technologies applicable to NMR spin-echo amplitude estimation are disclosed. Example methods may calibrate for distortion of a shape and estimated amplitude of measured NMR spin or gradient echoes. NMR spin or gradient echo measurements may be performed on a sample. The measured NMR spin or gradient echoes may be used to calculate an echo-shape calibration factor. The echo-shape calibration factor may estimate an effect of echo shape on estimated spin or gradient echo amplitude(s) of the NMR spin or gradient echoes. The echo-shape calibration factor may be used to correct for underestimation or overestimation of the spin or gradient echo amplitude(s).