Dynamic Shimming for MRI Magnet Positioning
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Solution Overview
Problem
Magnetic resonance apparatuses face challenges in maintaining a homogeneous magnetic field due to external influences and variable positions, which current shimming methods cannot effectively address, especially when the magnet's position changes relative to the patient's body or examination region.
Innovation Solution
Incorporating sensors to determine the spatial location of the magnetic resonance apparatus within the examination room and using a positioning apparatus to adjust the magnet's position and orientation, coupled with a method to dynamically adjust shim parameters based on a magnetic field database to compensate for inhomogeneities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the magnetic resonance apparatus is moved to different positions in the examination room, then the adaptability to different patient positions and examination regions is improved, but the magnetic field homogeneity deteriorates due to external influences and position-dependent inhomogeneities
Solution Approach 1:
The patent implements dynamic shimming by continuously monitoring the magnetic field homogeneity through sensors and automatically adjusting shim coil currents based on detected inhomogeneities. This dynamic adaptation allows the system to maintain field homogeneity across different positions and patient configurations, resolving the contradiction between adaptability and field stability
Solution Approach 2:
The system changes electrical parameters (shim coil currents) in response to position changes and detected field inhomogeneities. By dynamically adjusting these parameters based on sensor feedback and database lookups, the system maintains magnetic field homogeneity while adapting to various examination scenarios and patient positions
2Manufacturing precision
If separate shim coils are used to compensate for higher-order inhomogeneities, then the manufacturing precision of the magnetic field is improved, but the device complexity increases
Solution Approach 1:
The patent implements a universal shimming approach where gradient coils perform both their primary gradient function and secondary shimming function. By utilizing existing hardware for dual purposes and combining this with sensor-based detection and database-driven parameter selection, the system achieves high field precision without proportionally increasing device complexity
Solution Approach 2:
The system performs self-characterization by automatically mapping magnetic field inhomogeneities at different positions using sensors and storing this information in a database. This self-service capability eliminates the need for manual field mapping and enables automatic shimming parameter selection, reducing operational complexity while maintaining high precision
3Manufacturing precision
If small iron plates are mounted at prescribed positions to set the magnetic field, then the manufacturing precision is improved, but the ease of operation deteriorates when position changes are required
Solution Approach 1:
The patent replaces static iron plate configurations with dynamic electronic shimming using shim coils. This allows the magnetic field to be adjusted electronically rather than requiring physical repositioning of iron plates, thereby maintaining manufacturing precision while dramatically improving ease of operation when position changes are needed
Solution Approach 2:
The system substitutes mechanical adjustment of iron plates with electronic control of shim coil currents. This replacement of mechanical shimming with electronic shimming enables rapid, precise field adjustment without physical manipulation of components, resolving the contradiction between precision and operational ease
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 solution allows for precise adjustment of the magnetic field homogeneity even when the apparatus is moved, improving image quality and enabling imaging examinations on patients in various positions, including sitting or standing, while minimizing external interference.
Implementation Method 1
A magnetic resonance apparatus comprises a magnet (13) which is embodied to generate a magnetic field
Implementation Method 2
at least one sensor (23) which is embodied to determine a spatial location of the magnetic resonance apparatus (10) in the examination room
Implementation Method 3
shim elements, such as for example small iron plates and/or electronic shim coils, are used in order to obtain a main magnetic field that is as homogeneous as possible
Data Source
AI summary
A magnetic resonance apparatus may include at least one sensor and a controller. The magnetic resonance apparatus is positionable in an examination room. A spatial location of the magnetic resonance apparatus in the examination room can be determined using the sensor. In a method for supporting an adjustment of a shim parameter of a magnetic resonance apparatus, a current spatial location of the magnetic resonance apparatus in an examination room is determined using the sensor, and a shim parameter of at least one shim element of the magnetic resonance apparatus is determined based on the current spatial location of the magnetic resonance apparatus and information of a magnetic field database. The magnetic field database may include information about a spatial location of the magnetic resonance apparatus and also magnetic field data correlated with the spatial location.