Gradient Coil Unit Without Active Screening
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Solution Overview
Problem
Conventional gradient coil units in magnetic resonance devices require active screening with secondary coils, which reduces the internal diameter of the patient receiving region and increases energy consumption, while also generating eddy currents that can affect image quality.
Innovation Solution
A gradient coil unit designed without active screening, featuring a primary coil with a conductor structure that includes neutral regions with reduced current density, allowing for controlled eddy current fields and minimized eddy currents, thereby optimizing the patient receiving region size and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If secondary coils are added for active screening, then eddy currents are suppressed, but the internal diameter of the patient receiving region is reduced
Solution Approach 1:
The patent removes the secondary coil unit entirely from the gradient coil assembly, eliminating the space-consuming screening component while accepting controlled eddy current effects. The primary coil unit operates without active screening, extracting the harmful suppression function to achieve larger patient receiving region dimensions.
Solution Approach 2:
The conductor structure implements non-uniform current density distribution with neutral regions having reduced current density (less than 25% of maximum). This local variation in electrical properties allows the coil to generate the desired magnetic field gradient while minimizing eddy current generation in specific zones without requiring secondary coils.
2Object-affected harmful factors
If secondary coils are added for active screening, then eddy current fields are suppressed, but energy consumption increases
Solution Approach 1:
The patent eliminates the secondary coil unit and its associated gradient amplifier, removing the energy-consuming active screening subsystem. The system accepts controlled eddy current fields in exchange for significantly reduced power requirements and simplified energy delivery.
Solution Approach 2:
The conductor structure uses non-uniform current density distribution with neutral regions where current density is less than 25% of the maximum. This parameter variation in the electrical characteristics allows the primary coil to generate appropriate magnetic field gradients while minimizing eddy current generation, reducing overall energy consumption without active screening.
3Power
If current density is increased in the conductor structure, then magnetic field gradient strength is improved, but eddy currents increase
Solution Approach 1:
The conductor structure implements spatially varying current density with neutral regions having reduced current density (less than 25% of maximum) and other regions having higher current density. This local differentiation allows the coil to generate strong magnetic field gradients in regions where high current is beneficial while minimizing eddy currents in neutral regions where the conductor structure is optimized for reduced electromagnetic interference.
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
The gradient coil unit achieves a larger patient receiving region and reduced energy consumption compared to actively screened units, while minimizing eddy currents and improving image quality by effectively managing leakage fields.
Implementation Method 1
A primary coil is typically designed for generating a magnetic field gradient in one spatial direction. A magnetic field gradient is typically a first order and/or linear order magnetic field, in particular a magnetic field the amplitude of which rises in a linear manner along a spatial direction.
Implementation Method 2
In the driving of a primary coil, leakage fields are generated outside the gradient coil unit, said leakage fields interacting with conductive structures surrounding the gradient coil unit, whereby eddy currents arise.
Data Source
AI summary
A gradient coil unit is described that is designed as a hollow cylinder surrounding a patient receiving region in the longitudinal direction and is subdivisible into four quadrants, comprising a primary coil including a conductor structure that includes a geometric arrangement of an electrical conductor with a conductor cross-section arranged within a quadrant of the four quadrants. The quadrant comprises at least one neutral region, which is defined in the longitudinal direction between a first longitudinal position and a second longitudinal position, and characterized in that the current density averaged over the neutral region is less than 25% of the maximum current density averaged over the conductor cross-section within the neutral region. The gradient coil unit is free of a secondary coil and/or free of an active screening.