Magnetic Resonance Field Vector Correction
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges due to deviations from ideal magnetic field conditions, leading to geometric distortions and artifacts in images, caused by non-linear gradient fields and orthogonal components, which existing methods like dynamic field cameras struggle to accurately correct.
Innovation Solution
A method involving a magnetic field sensor unit to detect vectors at various positions, creating a vector field model using spherical harmonic basis functions, allowing for precise correction of magnetic fields and accounting for dynamic behavior, including eddy currents, to improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gradient coils are used to generate magnetic fields for spatial encoding, then magnetic resonance imaging can be performed, but geometric distortions and artifacts occur due to non-linear gradient fields and orthogonal components
Solution Approach 1:
The patent applies preliminary action by measuring and characterizing the magnetic field properties (including non-linearities and orthogonal components) before performing the actual magnetic resonance imaging. A field map is created in advance that documents the deviations from ideal gradient fields, which then serves as a reference for correcting image distortions during reconstruction
Solution Approach 2:
The patent implements feedback by using the measured field map information to adjust and correct the magnetic resonance image reconstruction process. The system continuously compares the actual magnetic field conditions against ideal conditions and applies compensatory corrections to eliminate geometric distortions and artifacts in the final images
2Ease of operation
If dynamic field cameras are used to measure magnetic fields, then field characterization is possible, but measurement precision is insufficient for accurate correction of geometric distortions
Solution Approach 1:
The patent applies segmentation by dividing the magnetic field measurement task into distinct components: measuring the main magnetic field, measuring gradient fields, and separately characterizing orthogonal components. This segmented approach allows each component to be measured and corrected with appropriate precision using specialized methods for each field type
Solution Approach 2:
The patent transitions from scalar magnetic field strength measurements to vector field measurements by incorporating directional information. The system measures not only the magnitude but also the direction of magnetic field vectors, enabling precise characterization of orthogonal components and their contribution to image distortions
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 more accurate and precise determination of magnetic fields, reducing geometric distortions and artifacts, thereby enhancing the quality of MRI images by correcting for non-ideal magnetic field conditions.
Implementation Method 1
A magnetic field sensor unit is used to detect a plurality of magnetic field vectors at different positions of the magnetic field
Implementation Method 2
a gradient coil unit of the magnetic resonance apparatus is used to generate gradient magnetic fields (e.g., gradient pulses) that are usually used for spatial encoding
Implementation Method 3
A further problem is associated with the eddy currents induced by the gradient coil unit in electrically conductive parts of the magnetic resonance apparatus
Data Source
AI summary
A method for ascertaining a magnetic field of at least one magnetic coil unit of a magnetic resonance apparatus, a magnetic resonance apparatus, and a computer program product are provided. According to the method, the magnetic field is generated by the at least one magnetic coil unit. A plurality of magnetic field vectors are detected at different positions of the magnetic field by a magnetic field sensor unit, where each magnetic field vector of the plurality of magnetic field vectors describes a strength, such as a magnitude, and a direction of the magnetic field at the respective position. The magnetic field is ascertained. To ascertain the magnetic field based on the plurality of magnetic field vectors, a model of a vector field is ascertained.