Non-linear Magnetic Field Gradients for MRI Spatial Resolution
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) methods using linear additional magnetic fields are limited by technical and physiological constraints, resulting in suboptimal spatial resolution and longer irradiation times for location-dependent changes in magnetization, which restricts the ability to achieve higher resolution and shorter measurement durations.
Innovation Solution
The use of non-linear additional magnetic fields with spatial gradients that are not constant at least at one point in time, combined with high-frequency pulses calculated based on location-dependent time profiles of these fields, allows for more precise and efficient location-dependent changes in magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear additional magnetic fields are used for location-dependent magnetization changes, then the method is simple to implement, but spatial resolution is limited and irradiation duration increases
Solution Approach 1:
The patent applies parameter changes by transitioning from linear to non-linear additional magnetic fields, fundamentally altering the field distribution parameters. This enables higher spatial resolution magnetization changes because non-linear fields provide more granular control over different spatial locations, allowing precise targeting of specific regions without requiring extended irradiation times across the entire examination volume.
Solution Approach 2:
The patent implements preliminary action by calculating the high-frequency pulses in advance based on predetermined non-linear additional magnetic field configurations. This pre-calculation approach allows the system to optimize pulse sequences for specific non-linear field patterns, enabling faster execution of location-dependent magnetization changes without requiring real-time computation during the actual irradiation process.
2Measurement precision
If linear additional magnetic fields are used, then the system is easier to control, but technical and physiological constraints limit performance
Solution Approach 1:
The patent applies dynamics by introducing time-varying non-linear additional magnetic fields that can be dynamically adjusted during the magnetization process. These fields are not static but evolve over time according to predetermined patterns, enabling flexible control of magnetization changes across different locations while managing the complexity through systematic field evolution rather than simultaneous complex spatial variations.
Solution Approach 2:
The patent uses calculated high-frequency pulses as an intermediary between the control system and the non-linear additional magnetic fields. These pre-calculated pulses serve as mediators that translate the complex non-linear field configurations into actionable magnetization changes, simplifying the control process by decoupling field generation from pulse application while maintaining precise spatial control.
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 higher spatial resolution and shorter irradiation durations for magnetization changes, overcoming the limitations of linear field methods while reducing technical and physiological challenges.
Implementation Method 1
exposing the examination object within the examination volume of a magnetic resonance measuring apparatus to an essentially static and homogeneous basic magnetic field, also referred to as the main magnetic field
Implementation Method 2
The associated alignment of the magnetic dipole moments of the atomic nuclei leads to magnetization within the object in the direction of the main magnetic field, which is referred to as longitudinal magnetization. In the MR examination (MR: magnetic resonance) this magnetization within the examination object is excited to a precession movement by irradiation of electromagnetic HF pulses
Implementation Method 3
a spatial coding, generally referred to as spatial coding, is imposed on the precession movements of the nuclear spins by temporally varying superimpositions of additional, location-dependent magnetic fields
Implementation Method 4
The transverse component of the precessing magnetization associated with the nuclear spins, also referred to below as transverse magnetization, induces voltage signals in one or more HF receiving antennas surrounding the examination object, which are also referred to as magnetic resonance signals
Data Source
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AI summary
A method for spatially changing the magnetization in an object, according to a specification within the framework of a magnetic resonance experiment, wherein high-frequency pulses are irradiated in combination with spatially and temporally varying additional magnetic fields, which are superimposed on the static and homogeneous background field of a magnetic resonance measuring apparatus aligned along a z-direction, is characterized in that non-linear additional magnetic fields are applied, the spatial gradient of which of the z-component is not constant at at least one time point of the irradiation, and that the high-frequency pulses to be irradiated are calculated in advance, wherein spatially calculated and/or measured temporal profiles of the field strengths of the additional magnetic fields in the area of the object are included in this calculation.This enables the change in magnetization with at least a locally higher spatial resolution and/or a shorter duration of exposure to the high-frequency pulses and additional magnetic fields than is possible with linear additional magnetic fields generated by conventional gradient systems. This is therefore possible, in particular, under the same technical and physiological constraints that currently limit the performance of known methods when using linear additional fields.