Dynamic Eddy Current Compensation in Magnetic Resonance Imaging
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Solution Overview
Problem
Current magnetic resonance (MR) methods suffer from undesirable eddy current effects caused by switched gradients, leading to off-resonance artifacts and reduced image quality, especially in sequences requiring strong gradients like diffusion imaging and HASTE sequences.
Innovation Solution
A method is introduced to dynamically determine and switch compensation gradients during the measurement process, checking for gradients exceeding a predefined threshold value and applying corresponding compensation gradients in subsequent repetitions to mitigate eddy current effects prospectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If strong gradients are switched to accelerate data acquisition (e.g., in diffusion imaging and HASTE sequences), then measurement speed is improved, but eddy current artifacts increase leading to reduced image quality
Solution Approach 1:
The patent applies preliminary anti-action by switching compensation gradients before the actual measurement gradients to counteract the eddy currents that will be generated. The control facility determines compensation gradients based on the planned measurement gradients and switches them in a preliminary phase, thereby preemptively抵消ing the harmful eddy current effects before they can degrade image quality.
Solution Approach 2:
The patent introduces compensation gradients as an intermediary element between the measurement gradients and the examination object. These compensation gradients act as a mediator that counteracts the eddy currents generated by the measurement gradients, thereby protecting the measurement process from the harmful effects without requiring changes to the primary measurement sequence.
2Manufacturing precision
If compensation gradients are switched to reduce eddy current artifacts, then image quality is improved, but the complexity of the gradient sequence increases
Solution Approach 1:
The patent applies preliminary action by determining and preparing the compensation gradients in advance based on the planned measurement gradients. The control facility calculates the required compensation gradients before the actual measurement sequence begins, allowing the system to automatically generate appropriate compensation without requiring complex real-time calculations during the measurement process.
Solution Approach 2:
The patent implements feedback by using information about the planned measurement gradients to determine the appropriate compensation gradients. The control facility monitors the gradient sequence and automatically adjusts the compensation gradients based on the expected eddy current effects, creating a closed-loop system that optimizes image quality while managing complexity.
3Measurement precision
If eddy currents are compensated in real-time during data acquisition, then measurement accuracy is improved, but the measurement time increases due to additional gradient switching
Solution Approach 1:
The patent applies periodic action by structuring the gradient sequence in repeating cycles that include both measurement gradients and compensation gradients. The control facility organizes the gradient switching in periodic patterns, allowing the system to efficiently alternate between data acquisition and eddy current compensation without requiring continuous additional time beyond the structured sequence.
Solution Approach 2:
The patent merges the eddy current compensation process with the data acquisition process by integrating compensation gradients into the measurement sequence itself. Rather than adding separate compensation steps, the system combines both functions into a unified gradient sequence, thereby achieving compensation without proportionally increasing total measurement time.
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 effectively reduces eddy current artifacts during data acquisition, enhancing the quality of reconstructed image data by compensating for eddy currents in real-time, thereby improving the accuracy and speed of MR imaging.
Implementation Method 1
the examination object is positioned for this purpose in a magnetic resonance device in a relatively strong static, homogeneous basic magnetic field, also called the B0 field
Implementation Method 2
radio frequency excitation pulses (RF pulses) are irradiated into the examination object, the triggered magnetic spin resonances are measured
Implementation Method 3
undesirable effects of eddy currents generated by switched gradients
Data Source
AI summary
Techniques are disclosed for creating measurement data of an examination object by means of magnetic resonance technology in a plurality of repetitions according to a pulse sequence pattern, existing information about gradients that have already been switched is considered to determine compensation gradients that are possibly to be switched in a following repetition for compensating eddy current effects. Such dynamic determination and switching of compensation gradients make it possible to dynamically compensate eddy currents. Consequently, the image quality of image data reconstructed from measurement data acquired using inventive compensation gradients is increased.