Modified Dixon Technique for Flexible Echo Time MRI
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Solution Overview
Problem
Conventional Dixon imaging techniques for MRI are limited by fixed echo times, reducing flexibility in sequence design and increasing scan times, which constraints the water-fat angle and affects the accuracy and efficiency of fat suppression and quantification.
Innovation Solution
A modified Dixon technique that measures signals at arbitrary echo times, calculates differential phase error candidates, and selects the appropriate candidate based on smoothness assumptions to reconstruct water and fat images, allowing for increased flexibility in protocol parameter selection and improved image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed echo times are used in conventional Dixon imaging, then the water-fat angle is constrained and phase errors are simplified, but scan time increases and flexibility in sequence design is reduced
Solution Approach 1:
The patent applies dynamics by transitioning from fixed, static echo times to arbitrary, flexible echo times that can be dynamically selected based on the specific imaging requirements. The system allows echo times to be adjusted and optimized for different clinical scenarios, enabling adaptive sequence design that balances scan time with image quality and fat suppression accuracy.
2Productivity
If fixed echo times are used in conventional Dixon imaging, then the acquisition protocol is simplified, but scan time increases
Solution Approach 1:
The patent implements parameter changes by allowing arbitrary selection of echo times (TE1 and TE2) rather than being constrained to fixed values. This enables optimization of the water-fat angle and phase error characteristics for each specific imaging scenario, improving scan efficiency by reducing the number of required acquisitions while maintaining or enhancing image quality.
3Adaptability or versatility
If arbitrary echo times are used, then flexibility in protocol parameter selection is increased, but complexity of phase error correction increases
Solution Approach 1:
The patent employs feedback mechanisms through iterative phase error correction algorithms that use the acquired signal data to refine and adjust phase corrections. The system calculates phase errors based on the arbitrary echo times selected, then uses this information to correct the images, creating a feedback loop that maintains accuracy despite the increased flexibility in echo time selection.
4Measurement precision
If conventional Dixon imaging with fixed echo times is used, then acquisition is simpler, but fat suppression accuracy is reduced
Solution Approach 1:
The patent applies preliminary action by carefully selecting and optimizing the echo times before data acquisition to achieve the desired water-fat angle and minimize phase errors. By pre-planning the echo time parameters based on the specific imaging requirements, the system achieves accurate fat suppression without requiring complex post-processing corrections.
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 reduces scan time, enhances image quality, and increases the flexibility of protocol parameter selection, leading to more efficient and accurate differentiation between water and fat tissues in MRI data.
Implementation Method 1
Different materials (e.g., fat and water) nuclei resonate or 'spin' back to their original positions at different rotational velocities. An echo is caused and detected by the MR scanner
Implementation Method 2
Dixon imaging, which is based on the different chemical shift of water and lipid protons and resulting phase differences between the signals from them at different echo times
Implementation Method 3
measuring a first signal (I1) and a second signal (I2) at different arbitrary echo times during a magnetic resonance (MR) scan of a subject
Data Source
AI summary
When distinguishing between fat and water in acquired MR data, a modified Dixon technique includes acquiring first and second signals Ii and I2, calculating the first and second components B and S of the signals Iχ and I2, where one of the first and second components corresponds to fat and the other corresponds to water, deriving two differential phase error candidates from them, and selecting a phase error candidate based on the assumption of smoothness of the disturbing field inhomogeneity. The exact determination of the absolute values of the water and fat components is then made by solving three signal equations for two variables that respectively correspond to water and fat, and is performed using for example a least square minimization with a Newton method.