Magnetic Resonance Gradient Slew Rate Control
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Solution Overview
Problem
Magnetic resonance systems face challenges in minimizing peripheral nerve stimulation caused by gradient field changes, which can lead to health risks, especially when the patient's position affects the severity of stimulation, and existing methods often rely on worst-case scenarios to comply with safety limits.
Innovation Solution
A method that dynamically adjusts the position of the examination object within the magnetic resonance system to optimize gradient field exposure, allowing for faster imaging sequences while ensuring exposure limits are not exceeded, by detecting and modifying the position based on exposure values relative to predetermined limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the gradient system performs field changes as quickly as possible to reduce measuring time and improve image quality, then the measuring time is reduced and image quality is improved, but peripheral nerve stimulation increases and may cause health risks
Solution Approach 1:
The patent implements dynamic slew rate limitation that adapts to the patient's position within the examination volume. The control facility continuously monitors position and adjusts the maximum permissible slew rate accordingly, allowing faster gradient switching when the patient is in safe positions and reducing slew rate when positions approach stimulation thresholds. This dynamic adjustment resolves the contradiction by optimizing measuring speed while preventing peripheral nerve stimulation through real-time position-based control.
Solution Approach 2:
The system changes the operational parameter (slew rate) based on the patient's position. By calculating position-dependent maximum slew rates and adjusting the gradient system's operating parameters dynamically, the system achieves faster imaging when safe and reduces stimulation risk when positions are unfavorable. This parameter adaptation resolves the contradiction between speed and safety.
2Reliability
If the worst case approach is always assumed to ensure compliance with safety limits, then patient safety is ensured, but imaging speed is reduced and measuring time increases
Solution Approach 1:
The system implements a feedback mechanism where the control facility continuously receives position information from the positioning system and adjusts the maximum permissible slew rate accordingly. This closed-loop control allows the system to operate at higher speeds when positions are safe and automatically reduces speed when approaching stimulation thresholds, resolving the contradiction between safety and productivity through intelligent feedback-based adaptation.
Solution Approach 2:
The control facility pre-calculates position-dependent maximum slew rates based on the examination protocol and patient position before executing gradient pulses. By determining safe operating parameters in advance for each position, the system can operate efficiently without conservative worst-case limitations while maintaining safety compliance.
3Productivity
If the patient position is adjusted to optimize gradient field exposure, then imaging speed can be increased, but system complexity increases due to position monitoring and dynamic adjustment requirements
Solution Approach 1:
The control facility serves multiple functions: it manages the gradient system, receives position information, calculates position-dependent slew rates, and executes the imaging protocol. By making the control facility multi-functional, the system achieves position-based optimization without requiring separate dedicated positioning control systems, thereby reducing overall system complexity while maintaining high imaging speed capability.
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
Enables faster imaging with reduced artifacts and minimized health risks by dynamically adjusting the examination object's position to maintain exposure within safe limits, thereby optimizing imaging sequences without endangering the patient.
Implementation Method 1
the gradient fields that vary over time induce currents in the human body
Data Source
AI summary
A control facility of a magnetic resonance system receives parameters of a measuring sequence from an operator. The parameters define an activation of a gradient system of the magnetic resonance system. The control facility detects an exposure of at least one body region of the examination object brought about by the activation of the gradient system. The exposure is detected as a function of the position in which the examination object is disposed in an examination volume of the magnetic resonance system.