Magnetic Resonance Gradient Compensation for Eddy Current Artifacts

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Solution Overview

Problem

Magnetic resonance systems using Turbo Spin-Echo sequences are prone to artifacts caused by eddy currents, which affect image quality due to their sensitivity to imperfections in the imaging process.

Innovation Solution

A method to avoid artifacts in magnetic resonance systems by determining compensation gradients based on both the loaded measurement protocol and system-specific data characterizing the gradient unit, which is used to switch gradients after the final RF refocusing pulse and before the next RF excitation pulse.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If TSE sequences are used to accelerate data capture, then productivity is improved, but measurement precision deteriorates due to increased sensitivity to eddy currents and timing instabilities

Engineering Contradiction:

Improvedata capture speedVSAvoidimage quality

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by calculating and storing compensation gradients in advance based on the specific TSE sequence parameters (turbo factor, echo train length, gradient amplitudes) before actual image acquisition. These pre-calculated compensation gradients are then applied during the sequence execution to counteract eddy current effects, thereby maintaining both high productivity and measurement precision

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If periodic gradient shapes are used in TSE sequences, then device complexity is reduced, but object-generated harmful factors increase due to cumulative eddy current effects

Engineering Contradiction:

Improvegradient waveform designVSAvoideddy current artifacts

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful eddy current effects into a beneficial compensation mechanism. By calculating compensation gradients that are equal in magnitude but opposite in direction to the expected eddy current gradients, the system transforms the problematic periodic gradient design into an opportunity for systematic artifact correction, thereby reducing harmful effects without increasing device complexity

Inventive Principle:

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

3Productivity

If multiple refocusing pulses are applied to produce multiple spin-echo signals, then productivity is improved, but reliability deteriorates due to accumulated eddy current effects affecting subsequent excitations

Engineering Contradiction:

Improvemeasurement timeVSAvoidsignal consistency

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent implements feedback by using the known sequence parameters and gradient waveforms to predict eddy current effects, then applying compensation gradients that counteract these predicted effects. This closed-loop approach ensures that each refocusing pulse and subsequent excitation maintains signal consistency, thereby improving reliability while preserving the productivity gains from multiple echoes

Inventive Principle:

Principle #23Feedback

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 significantly reduces perturbing effects from eddy currents, leading to improved image quality by minimizing artifacts in the reconstructed image data.

Implementation Method 1

Rapidly switched magnetic gradient fields, or gradients for short, are overlaid on the main magnetic field in order to spatially encode the measurement data

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

radio-frequency excitation pulses (RF pulses) are irradiated into the object under examination, the triggered nuclear spin resonances are measured as k-space data

Methodology Applied

Scientific EffectElectromagnetic radiation:

Implementation Method 3

the object under examination is to this end positioned in a magnetic resonance device in a comparatively strong static, homogeneous main magnetic field, also known as B0 field

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Data Source

PatentUS12313717B2Avoidance of artifacts in measurement data captured using a magnetic resonance system

Publication Date: 2025.05.27 SIEMENS HEALTHINEERS AG

AI summary

A method for avoiding artifacts in measurement data captured using a magnetic resonance system which has a gradient unit. The method includes loading data which characterizes the gradient unit of the magnetic resonance system; loading a measurement protocol to be used for capturing the measurement data, wherein the measurement protocol includes gradients to be switched and RF excitation pulses and RF refocusing pulses to be irradiated, wherein, after irradiation of an RF excitation pulse, a train of at least two RF refocusing pulses is irradiated and measurement data is captured after each RF refocusing pulse; determining compensation gradients which, after the capture of the measurement data, are to be switched after a final RF refocusing pulse of the train of RF refocusing pulses associated with the RF excitation pulse and before a following RF excitation pulse as a function of the loaded measurement protocol and of the data which characterizes the gradient unit; and carrying out the measurement protocol using the determined compensation gradients.