Magnetic Resonance Tomography Magnet Field Re-establishment
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Solution Overview
Problem
Magnetic resonance tomography (MRT) devices with low Helium Inventory (LHI) or dry magnets face challenges in accurately re-establishing the magnetic field after a ramp-down mode, leading to reduced transmission performance due to mismatch between the center frequency of emitted radiation and the receiving coil, especially in low-field systems.
Innovation Solution
A method that transfers the magnet from an operating to a non-operating state and back in ramp-down and ramp-up modes, using a reference parameter (current) to calibrate and adjust the magnetic field, allowing for accurate re-establishment of the desired magnetic field without direct magnetic field measurement, utilizing a shunt in the magnetic power supply for current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the magnetic field is re-established by directly ramping up the current to the previous operating value, then the ramp-up process is simple and fast, but the magnetic field accuracy is poor leading to center frequency mismatch
Solution Approach 1:
The patent introduces an intermediary parameter (reference parameter different from magnetic field, such as voltage, temperature, or current) that correlates with the magnetic field strength. This intermediary serves as a proxy for measuring and controlling the magnetic field during ramp-up, avoiding the need for direct magnetic field measurement while maintaining accuracy. The reference parameter acts as a mediator between the control system and the magnetic field, enabling indirect but precise control.
Solution Approach 2:
The patent replaces direct magnetic field measurement systems with alternative measurement approaches using different physical quantities (electrical, thermal, or optical parameters). This substitution eliminates the need for complex magnetic field sensors and measurement infrastructure, using instead simpler and more reliable measurement technologies that indirectly reflect the magnetic field state through calibrated relationships.
2Device complexity
If the Helium system is removed to reduce costs and simplify the system, then the device complexity and cost are reduced, but the reliability decreases due to risk of quench
Solution Approach 1:
The patent implements preliminary monitoring and control actions during the ramp-up process to detect and respond to conditions that could lead to quench before they occur. By continuously observing reference parameters and comparing them against calibrated target values, the system can identify approaching dangerous conditions and adjust the ramp-up rate or terminate the process preventively, ensuring safe operation of the Helium-free magnet.
3Ease of operation
If the ramp-up mode is completed based on reaching a predetermined current value, then the control is simple, but the magnetic field accuracy is insufficient due to drift from previous field state
Solution Approach 1:
The patent implements a feedback control mechanism where the reference parameter is continuously monitored during ramp-up and compared against a target value that was calibrated during the previous operating state. The ramp-up process automatically adjusts based on this feedback, slowing down or stopping when the reference parameter approaches the target, thereby achieving accurate magnetic field re-establishment without complex manual intervention while maintaining simplicity in the control logic.
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 cost-efficient and accurate re-establishment of the magnetic field, reducing downtime and eliminating the need for complex measuring systems, while maintaining optimal center frequency matching for the receiving coil, particularly beneficial for low-field systems.
Implementation Method 1
For superconducting magnets, the most common cryogenic solution is to cool the magnet in a Helium bath
Implementation Method 2
a magnet defining by its magnetic field a center frequency for the radiation emitted by a patient or a probe
Implementation Method 3
a receiving coil of the MRT-device is adapted for receiving the emitted radiation
Implementation Method 4
utilizing a shunt in the magnetic power supply for current measurement
Data Source
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AI summary
The present invention suggests a method for adjusting a magnetic field of a magnetic resonance tomography (MRT)-device (1) having a magnet (2), comprising: - transferring the magnet (2) from an operating state to a non-operating state in a ramp-down mode (10); - subsequently transferring the magnet (2) from the non-operating state to the operating state in a ramp-up mode (20) ; - observing (20) a reference parameter different from the magnetic field; - setting (25) a target value for the reference parameter; - comparing (35) the observed reference parameter to the target value; and - finishing (40) the ramp-up mode when the reference parameter reaches the target value.