Mobile MRI Shield Thermal Compensation for Field Homogeneity
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Solution Overview
Problem
Mobile magnetic resonance tomography systems face challenges in maintaining image quality due to temperature-induced changes in the susceptibility and expansion of the iron shield, leading to inhomogeneities in the static magnetic field, especially in constrained spaces like trailers where complete thermal and mechanical insulation is impractical.
Innovation Solution
A temperature measurement system with sensors at multiple points on the shield feeds data to a compensation system, which uses heating/cooling elements and shim coils to correct temperature differences and restore magnetic field homogeneity, potentially adjusting the frequency of the transmit coil to compensate for field shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the iron shield is mounted in a mobile MRT system, then the system can be transported to deployment locations, but temperature changes cause susceptibility changes and expansion in the shield, disrupting magnetic field homogeneity
Solution Approach 1:
The patent applies parameter changes by using temperature sensors to detect temperature variations in the iron shield and adjusting the current through compensation coils to counteract the magnetic field inhomogeneity caused by thermal expansion and susceptibility changes. This dynamic adjustment of electrical parameters compensates for environmental temperature changes, maintaining magnetic field homogeneity despite the mobile system's exposure to varying temperatures.
2Object-affected harmful factors
If additional heat insulation is provided in the external walls of the trailer, then thermal shielding is improved, but space requirements and external dimensions are increased
Solution Approach 1:
The patent replaces the mechanical/physical approach of adding thick thermal insulation layers with an active compensation system using temperature sensors and compensation coils. Instead of mechanically increasing the trailer's insulation thickness (which would increase volume), the system uses electrical compensation to counteract thermal effects, maintaining magnetic field homogeneity without additional physical space.
3Manufacturing precision
If the iron shield is completely thermally and mechanically insulated, then magnetic field homogeneity is maintained, but the system becomes more complex and space-consuming
Solution Approach 1:
The patent implements a feedback control system where temperature sensors continuously monitor the temperature of the iron shield, and the compensation system adjusts the current through compensation coils based on this temperature data. This closed-loop feedback mechanism maintains magnetic field homogeneity by dynamically compensating for thermal effects, replacing the need for complex passive insulation structures with a simpler active control system.
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 improves image quality by neutralizing thermal influences on the magnetic field, using cost-effective temperature sensors and heating elements, and allows continuous compensation during scans, optimizing performance in varying environmental conditions.
Implementation Method 1
a temperature measurement is taken by a temperature measuring system at a plurality of points on the shield
Implementation Method 2
The temperatures measured here are forwarded to a compensation system in which a temperature profile may now be generated that enables a targeted compensation of the temperature fluctuations
Implementation Method 3
a plurality of heating and/or cooling elements of the compensation system
Implementation Method 4
MRT is based on very strong magnetic fields, generated in a magnetic resonance tomography (MRT) system
Implementation Method 5
alternating magnetic fields in the radio frequency range by which specific atomic nuclei (mostly the hydrogen nuclei/protons) in the body are excited into resonance, thereby inducing an electrical signal in a receiver circuit
Implementation Method 6
excited into resonance, thereby inducing an electrical signal in a receiver circuit
Implementation Method 7
the shielding iron expands as a result of its being heated, which likewise affects the homogeneity of the static magnetic field
Implementation Method 8
The change in temperature of the iron leads to a change in the susceptibility of the iron and consequently to a change in magnetization
Data Source
AI summary
A method for operating a mobile magnetic resonance tomography system having magnets and/or coils generating a magnetic field and a shield surrounding the magnets and/or coils is intended to enable an optimal image quality during the examination and at the same time have a small space requirement. For this purpose, a temperature is measured at a plurality of points on the shield by a temperature measuring system, where measured data of the temperature measuring system is sent to a compensation system, and where effects of temperature differences on the homogeneity of the magnetic field are compensated by the compensation system.