Multi-Peak Spectral Model for MRI Water-Fat Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current magnetic resonance imaging (MRI) methods for separating two dominant chemical species, such as water and fat, are limited in accuracy and efficiency, especially in time-critical applications like abdominal imaging, due to their reliance on simple spectral models and sensitivity to main field inhomogeneities.
Innovation Solution
The method incorporates multi-peak spectral models for at least one of the chemical species, allowing for more accurate and efficient separation by solving a system of complex equations to derive separate signal datasets, which can be obtained from just two images, regardless of their phase, using a biquadratic equation and regional iterative phasor extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If simple spectral models are used for chemical species separation, then the imaging process is fast and simple, but the separation accuracy deteriorates and residual signals remain
Solution Approach 1:
The patent changes the spectral model parameters from simple single-peak models to complex multi-peak spectral models that accurately represent the chemical species. This involves incorporating multiple resonance frequencies and relative intensities for each chemical species, transforming the separation process from a simple algebraic operation to a sophisticated spectral fitting process that resolves overlapping signals with high precision while maintaining computational efficiency through optimized algorithms.
2Measurement precision
If complex spectral models are used for chemical species separation, then separation accuracy improves, but the computational complexity and processing time increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the spectral characteristics of chemical species, including their multi-peak structures, relative intensities, and phase relationships. These pre-computed spectral templates are then used during the imaging process to rapidly fit and separate signals without performing complex real-time calculations, thus achieving high separation accuracy while minimizing computational burden during actual operation.
Solution Approach 2:
The patent implements feedback through an iterative refinement process where the separation algorithm initially uses a simplified model, then progressively refines the spectral parameters based on the residual errors and actual signal characteristics. This feedback loop allows the system to adaptively optimize the spectral model fitting, improving separation accuracy while controlling computational complexity by stopping iterations when convergence criteria are met.
3Productivity
If simple separation methods are used, then processing is fast, but sensitivity to main field inhomogeneities increases leading to poor separation quality
Solution Approach 1:
The patent addresses sensitivity to main field inhomogeneities by changing the modeling approach to include explicit phase parameterization that accounts for field variations. The complex spectral model incorporates phase terms that can be simultaneously fitted with amplitude parameters, allowing the algorithm to distinguish between phase variations due to field inhomogeneities and true spectral differences between chemical species. This maintains processing speed while significantly improving separation quality in the presence of field inhomogeneities.
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 enhances the quality and speed of signal separation for two chemical species, providing high-quality water-fat separation with reduced residual fat signal in water images and improved fat suppression, applicable in most clinical MR devices.
Implementation Method 1
The magnetic field produces different energy levels for the individual nuclear spins in dependence on the applied magnetic field strength which spins can be excited (spin resonance) by application of an alternating electromagnetic field (RF field) of defined frequency, the so called Larmor frequency or MR frequency.
Implementation Method 2
the magnetization performs a precessional motion about the z-axis
Implementation Method 3
constant magnetic field gradients extending along the three main axes are superposed on the uniform magnetic field, leading to a linear spatial dependency of the spin resonance frequency
Implementation Method 4
Any variation of the magnetization can be detected by means of receiving RF antennas, which are arranged and oriented within an examination volume of the MR device in such a manner that the variation of the magnetization is measured in the direction perpendicularly to the z-axis.
Implementation Method 5
an additional dimension, the chemical shift dimension, is defined and encoded by acquiring a couple of images at slightly different echo times
Data Source
Figure 1
AI summary
The invention relates to a method of imaging at least two chemical species using magnetic resonance imaging with signal separation for two chemical species resulting in separate signal datasets for these two chemical species, the method comprising: acquiring first and second echo data at different echo times resulting in a first and second acquired complex dataset, modelling the first and second acquired dataset by employing a spectral signal model of at least one of the chemical species, said modelling resulting in a first and second modelled complex dataset, said first and second modelled dataset comprising a first and second phase error and the separate signal datasets for the two chemical species, - determining from the first and second acquired dataset and the first and second modelled dataset the separate signal datasets for the two chemical species.