Passively Shielded Gradient Coil for Compact MR Scanners

Solution Overview

Problem

Existing magnetic resonance scanners face issues with eddy currents generated by gradient coils, which degrade image quality and impose space and cost limitations due to the need for active shielding and complex eddy current compensation mechanisms.

Innovation Solution

A magnetic resonance scanner with a managed eddy current structure that provides passive magnetic shielding by directing eddy currents through inductive coupling, using conducting control surfaces to cancel external magnetic fields and reduce the need for active shielding, allowing for unshielded gradient coils and smaller scanner designs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an actively shielded gradient coil is used to reduce eddy currents, then image quality is improved, but device complexity and space requirements increase

Engineering Contradiction:

Improveimage qualityVSAvoidgradient coil structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent converts the harmful eddy currents into a beneficial shielding mechanism. A conductive shield is positioned between the gradient coil and the magnet bore, where eddy currents generated in the shield by the gradient coil's magnetic field actually provide the shielding effect. This transforms the normally harmful eddy currents into the desired magnetic shielding, eliminating the need for complex active shielding coils while maintaining or improving image quality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If an actively shielded gradient coil is used to reduce eddy currents, then magnetic field uniformity is improved, but scanner size increases

Engineering Contradiction:

Improvemagnetic field uniformityVSAvoidscanner bore size

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent converts the harmful eddy currents into a beneficial shielding mechanism. A conductive shield is positioned between the gradient coil and the magnet bore, where eddy currents generated in the shield by the gradient coil's magnetic field actually provide the shielding effect. This transforms the normally harmful eddy currents into the desired magnetic shielding, eliminating the need for complex active shielding coils while maintaining or improving image quality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If eddy current compensation mechanisms are added to reduce image degradation, then image quality is improved, but device complexity and cost increase

Engineering Contradiction:

Improveimage qualityVSAvoidcompensation mechanism

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent converts the harmful eddy currents into a beneficial shielding mechanism. A conductive shield is positioned between the gradient coil and the magnet bore, where eddy currents generated in the shield by the gradient coil's magnetic field actually provide the shielding effect. This transforms the normally harmful eddy currents into the desired magnetic shielding, eliminating the need for complex active shielding coils while maintaining or improving image quality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Reliability

If a conductive shield is positioned between the gradient coil and magnet bore to reduce eddy currents, then magnetic field uniformity is improved, but the shield may heat up due to eddy current generation

Engineering Contradiction:

Improvemagnetic field uniformityVSAvoidshield temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent converts the harmful eddy currents into a beneficial shielding mechanism. A conductive shield is positioned between the gradient coil and the magnet bore, where eddy currents generated in the shield by the gradient coil's magnetic field actually provide the shielding effect. This transforms the normally harmful eddy currents into the desired magnetic shielding, eliminating the need for complex active shielding coils while maintaining or improving image quality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 passive shielding effectively reduces external magnetic field penetration and internal field non-uniformity, minimizing image quality degradation and scanner size while lowering costs and simplifying the design.

Implementation Method 1

a managed eddy current structure (110) which is inductively coupled to an otherwise unshielded gradient coil (108)

Methodology Applied

Scientific EffectInductive coupling: Electromagnetic Induction

Implementation Method 2

provide passive magnetic shielding for the gradient coil (108) as a result of the inductive coupling

Methodology Applied

Scientific EffectEddy currents: Eddy Currents

Data Source

PatentEP4300123B1Magnetic resonance scanner with passively shielded gradient coil

Publication Date: 2025.10.29 SIEMENS HEALTHCARE LTD

Figure 1~2
Figure 3~4

AI summary

The present disclosure relates to a magnetic resonance 'MR' scanner (100) utilising a passive magnetic shielding technique. The scanner (100) comprises a gradient coil (108) inductively coupled to a managed eddy current structure (110) which establishes passive magnetic shielding for the gradient coil (108) as a result of the inductive coupling. The present disclosure represents a paradigm shift in the way in which MR scanners may be magnetically shielded.