MRI Shim Unit Segmentation for Field Homogeneity
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in maintaining the homogeneity of the primary magnetic field due to variations caused by the subject being examined, leading to substandard image quality.
Innovation Solution
A method involving multiple scanning blocks with distinct shim settings is implemented to adjust and optimize the shim unit's current distribution, allowing for real-time frequency adjustments during the MRI process, matching shim settings to specific imaging volumes and breath-holding cycles, thereby improving the homogeneity of the primary magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single shim setting is used for the entire examination, then the device operation is simple, but the homogeneity of the primary magnetic field deteriorates when examining different body regions
Solution Approach 1:
The examination volume is divided into multiple scanning blocks, each with its own optimized shim settings. This segmentation allows different regions of the body to be examined with region-specific shim configurations, improving magnetic field homogeneity for each specific examination area while maintaining overall system simplicity through automated switching between predefined shim settings.
Solution Approach 2:
The shim settings are made dynamic by automatically selecting and switching between different pre-calculated shim configurations based on the current scanning block being examined. This dynamic adaptation allows the system to optimize magnetic field homogeneity for different body regions without requiring manual reconfiguration, resolving the contradiction between operational simplicity and field stability.
2Stability of the object's composition
If frequency adjustments are performed repeatedly during examination, then the homogeneity of the primary magnetic field is improved, but the examination time increases
Solution Approach 1:
Multiple different shim settings are pre-calculated and stored before the examination begins, each optimized for specific scanning blocks or body regions. During the actual examination, the system simply switches between these pre-prepared settings based on the current scanning block, eliminating the need for repeated frequency adjustments and measurements during the examination, thus reducing examination time while maintaining field homogeneity.
Solution Approach 2:
Instead of continuous or repeated frequency adjustments, the system implements periodic shim setting changes synchronized with the scanning block structure. Each shim setting is applied for the duration of its corresponding scanning block, creating a rhythmic pattern of adjustment that minimizes interference with the imaging process and reduces total adjustment time.
3Stability of the object's composition
If multiple different shim settings are used for different scanning blocks, then the homogeneity of the primary magnetic field is improved, but the device complexity increases
Solution Approach 1:
All necessary shim settings for different scanning blocks are pre-calculated and stored in memory before the examination begins. The control unit automatically retrieves and applies the appropriate pre-calculated settings based on the current scanning block, eliminating the need for complex real-time calculations or manual configurations during the examination. This approach maintains improved field homogeneity while keeping the operational interface simple.
Solution Approach 2:
The control unit automatically manages the switching between different shim settings based on the scanning block information, without requiring manual intervention from the operator. The system serves itself by autonomously selecting the optimal shim configuration for each scanning block, reducing the operational complexity for the user while maintaining multiple optimized settings for different examination regions.
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 enhances the homogeneity of the primary magnetic field, resulting in improved image quality and reduced examination time, increasing patient comfort by minimizing the need for repeated frequency adjustments.
Implementation Method 1
electrical shim coils, when driven with different shim currents, generate different compensation magnetic fields in order to improve the homogeneity
Implementation Method 2
the nuclear spins of particular atoms resonantly excited by the radio-frequency pulses are tilted by a defined flip angle with respect to the magnetic field lines of the primary magnetic field
Implementation Method 3
the nuclear spins of particular atoms resonantly excited by the radio-frequency pulses are tilted by a defined flip angle with respect to the magnetic field lines of the primary magnetic field
Implementation Method 4
When the nuclear spins are relaxed, radio-frequency signals (e.g., magnetic resonance signals) are emitted, received by suitable radio-frequency antennas, and processed further
Data Source
AI summary
In order to provide an improved homogeneity of a primary magnetic field during a magnetic resonance imaging process, a method for magnetic resonance imaging of a subject under examination using a magnetic resonance device includes an acquisition of magnetic resonance image data in a plurality of scanning blocks. Different shim settings are set in each case for the plurality of scanning blocks.