Eddy Current Compensation in Magnetic Resonance Sequences
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Solution Overview
Problem
Eddy currents in magnetic resonance apparatuses lead to artifacts in imaging measurements, requiring longer repetition times to decay, which increases measurement time and may necessitate sequence adaptations.
Innovation Solution
A method for automatically compensating eddy currents using a compensation computing unit that generates eddy current compensation gradient pulses by analyzing original magnetic resonance sequence data, inserting these pulses into the sequence to cancel out eddy-current induced field perturbations, allowing for real-time adaptation without modifying the original sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If longer effective repetition times are chosen to allow eddy currents to decay, then eddy current artifacts are reduced, but measurement time increases
Solution Approach 1:
The patent applies preliminary anti-action by computing and inserting eddy current compensation gradient pulses into the magnetic resonance sequence before the actual measurement occurs. The compensation computing unit calculates the expected eddy current effects based on the gradient waveform, then pre-inserts compensating gradients that generate opposite eddy currents to cancel out the harmful artifacts, allowing shorter repetition times without sacrificing image quality
Solution Approach 2:
The system performs preliminary computation of eddy current information and preparation of compensation gradients before the magnetic resonance measurement begins. The compensation computing unit processes the gradient waveform in advance to determine the appropriate compensation parameters, so that when the actual measurement occurs, the compensation is already in place and no additional measurement time is required
2Adaptability or versatility
If eddy current compensation is implemented, then sequence adaptability is improved, but device complexity increases
Solution Approach 1:
The patent introduces a compensation computing unit as an intermediary layer between the gradient waveform input and the magnetic resonance sequence execution. This intermediate processing unit computes eddy current compensation parameters and generates compensation gradients without requiring modifications to the original sequence design, thereby maintaining sequence versatility while adding compensation capability through a dedicated intermediate component
Solution Approach 2:
The system implements self-service by automatically computing and applying eddy current compensation without requiring manual sequence adaptation or external intervention. The compensation computing unit autonomously processes the gradient waveform, calculates the necessary compensation parameters, and inserts the appropriate compensation gradients into the sequence, making the system self-sufficient in eliminating eddy current artifacts
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 straightforward, sequence-independent eddy current compensation, reducing measurement time and eliminating the need for specific sequence adaptations, particularly effective in low field strengths where eddy current impacts are significant.
Implementation Method 1
For spatial encoding of the magnetic resonance signals, a (mostly linear) magnetic field gradient (e.g., called a 'gradient field' or 'gradient' for short) may be superimposed on a homogeneous main magnetic field
Implementation Method 2
Eddy currents are generated by time-varying magnetic fields, in particular by ramps of gradient pulses
Implementation Method 3
The compensation computing unit computes from this eddy current information at least one eddy current compensation gradient pulse for compensating the eddy currents
Data Source
AI summary
Methods for automatically compensating eddy currents in a magnetic resonance apparatus include determining modified magnetic resonance sequence data by a compensation computing unit and performing a magnetic resonance measurement in which a gradient generating system generates magnetic field gradients based on the modified magnetic resonance sequence data. The determining of the modified magnetic field gradient includes: receiving original magnetic resonance sequence data of a predetermined magnetic resonance sequence; computing eddy current information about eddy currents that would be produced in the magnetic resonance apparatus by applying the original magnetic resonance sequence data; computing, based on the computed eddy current information, at least one eddy current compensation gradient pulse for compensating the eddy currents; generating modified magnetic resonance sequence data by inserting the at least one eddy current compensation gradient pulse into the original magnetic resonance sequence data; and outputting the modified magnetic resonance sequence data to the gradient generating system.