Diffusion Gradient Coil Orientation for Torque Cancellation
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Solution Overview
Problem
In magnetic resonance imaging, diffusion gradient coils experience torques and induced currents due to interactions with the basic magnetic field and gradient fields, leading to vibrations, eddy currents, and potential hardware failures, which can degrade image quality and cause unpleasant sensations for patients.
Innovation Solution
The diffusion gradient coil is positioned with its conductor loops oriented orthogonally to the basic magnetic field and further gradient fields, allowing for the cancellation or substantial cancellation of torques and induced currents, thereby reducing disturbances and malfunctions during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the diffusion gradient coil is positioned to generate strong local magnetic fields, then the field strength is improved, but torques are produced that cause rotational movements and vibrations
Solution Approach 1:
The patent applies asymmetry by orienting the conductor loops of the diffusion gradient coil at specific asymmetric angles (e.g., 45 degrees) relative to the gradient fields. This asymmetric orientation causes the torques and induced voltages from different gradient field components to partially cancel each other, reducing the net harmful effects while maintaining the coil's ability to generate strong local magnetic fields for diffusion weighting.
Solution Approach 2:
The patent implements a counterweight principle by using multiple conductor loops oriented at different angles. The torques and induced voltages generated by each loop act in opposing directions, effectively canceling each other out. This allows the coil to maintain strong field generation capability while neutralizing the harmful rotational movements and vibrations.
2Adaptability or versatility
If the diffusion gradient coil operates in the presence of gradient fields, then imaging functionality is maintained, but induced voltages cause heating and field disturbances
Solution Approach 1:
The conductor loops are oriented at specific asymmetric angles (e.g., 45 degrees) relative to the gradient field directions. This asymmetric arrangement ensures that the induced voltages from different gradient field components (Gx, Gy, Gz) do not add constructively but instead partially cancel, reducing the total induced voltage, heating, and field disturbances while preserving imaging functionality.
Solution Approach 2:
The patent converts the potentially harmful induced voltages into a beneficial cancellation effect. By carefully selecting the orientation angles of the conductor loops, the induced voltages from different gradient fields are transformed from harmful additive effects into beneficial canceling effects, reducing net heating and field disturbances while maintaining the necessary imaging capability.
3Area of stationary object
If the diffusion gradient coil is placed close to the field of view for better imaging, then image coverage is improved, but even small eddy currents lead to disturbances that degrade image quality
Solution Approach 1:
The asymmetric orientation of conductor loops (e.g., at 45 degrees to gradient fields) reduces the magnitude of eddy currents induced during imaging sequences. This allows the coil to be positioned closer to the field of view for better image coverage while the reduced eddy current levels prevent the degradation of image quality that would otherwise occur.
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 arrangement effectively minimizes torques and induced currents, preventing vibrations, heating, and image quality degradation, while ensuring safe and reliable operation of the magnetic resonance device.
Implementation Method 1
a diffusion gradient coil serves to generate a strong magnetic field locally by means of a diffusion pulse
Implementation Method 2
As a result of the interaction of the currents in the diffusion gradient coil with the basic magnetic field of the magnetic resonance device, torques can be produced that act on the diffusion gradient coil
Implementation Method 3
If strong rotational movements of the diffusion gradient coil take place due to the torques, then vibration-induced eddy currents can be formed in parts of the magnetic resonance device
Implementation Method 4
the diffusion gradient coil is exposed during its use to the fields of the gradient coils, in which case voltages can be induced reciprocally in the coils due to the variation with time of the gradient fields and/or of the diffusion gradient field generated by the diffusion gradient coil
Implementation Method 5
If a flow of current also results due to the coupled-in voltages, then eddy currents, and in particular those induced in the diffusion gradient coil, can lead to a heating of the diffusion gradient coil
Data Source
AI summary
A magnetic resonance device is disclosed including a patient receiving zone, at least one diffusion gradient coil, at least one magnet for generating a basic magnetic field, and a plurality of gradient coils for generating gradient fields overlaying the basic magnetic field. The basic magnetic field extends substantially along a first direction in the patient receiving zone and a first gradient of a first gradient field runs in the first direction and at least one further gradient of a further gradient field runs in a further direction orthogonal to the first direction. The diffusion gradient coil has at least one conductor loop running in one plane or a plurality of conductor loops each running in parallel planes.