Magnetic Field Sensor Positioning for MRI Bed Alignment
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Solution Overview
Problem
Magnetic resonance tomography systems face challenges in accurately positioning patient beds within homogeneous magnetic fields, especially when examining larger body regions, due to variations in the static magnetic field and the need for precise alignment to ensure high-quality imaging.
Innovation Solution
A positioning device equipped with multiple magnetic-field-strength sensors along its axis, which can move relative to the magnetic resonance tomography system, uses these sensors to determine its position within the magnetic field by measuring the static magnetic field strength and gradient, allowing for precise alignment and calibration to achieve accurate positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cable pulls with encoders are used to track patient bed position, then position information can be obtained, but play occurs on direction changes and the relationship between encoder position and magnetic field must be established separately
Solution Approach 1:
The patent replaces the mechanical cable pull and encoder system with a magnetic field-based sensing system. Magnetic field strength sensors (such as Hall sensors) directly measure the static magnetic field strength at different positions, eliminating the mechanical connection and its associated play. The system substitutes mechanical position tracking with magnetic field characterization, where the relationship between position and magnetic field is inherent rather than requiring separate calibration.
2Adaptability or versatility
If the patient bed is moved through the homogeneous magnetic field region to examine larger body regions, then larger areas can be imaged, but the relationship between encoder position and magnetic field may change between examinations
Solution Approach 1:
The system performs self-calibration by automatically characterizing the magnetic field at multiple positions using the magnetic field strength sensors. The control unit stores the relationship between sensor positions and measured magnetic field strengths, creating a position-specific magnetic field profile. This self-service approach eliminates the need for manual recalibration between examinations, as the system autonomously adapts to any changes in the magnetic field environment.
Solution Approach 2:
The patent utilizes changes in magnetic field strength parameters at different positions to determine bed location. By measuring the static magnetic field strength (which varies predictably with position) using magnetic field strength sensors, the system translates magnetic field parameter changes into precise position information, enabling accurate tracking throughout the examination region.
3Measurement precision
If magnetic field strength sensors are used to determine position, then direct magnetic field measurement is achieved, but multiple sensors are required to account for production tolerances and ensure accuracy
Solution Approach 1:
The patent divides the position measurement function across multiple magnetic field strength sensors positioned at known locations along the patient bed. Each sensor independently measures the magnetic field strength at its specific position. The control unit processes signals from multiple sensors to determine the overall bed position, using the segmented measurements to compensate for individual sensor tolerances and achieve higher overall accuracy through redundancy and cross-validation.
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 enables precise and accurate positioning of the patient bed within the magnetic resonance tomography system, improving the operator's ability to correctly position the bed and enhancing the quality of imaging by accounting for production tolerances and magnetic field variations.
Implementation Method 1
Hall sensors are, for example, conceivable, but another possibility would be field probes based on electron or nuclear spin or devices based on an induction effect
Implementation Method 2
Magnetic resonance tomography systems are imaging devices that, in order to depict an examination object, align nuclear spins of the examination object with a strong outer magnetic field
Implementation Method 3
With the aid of magnetic gradient fields, spatial encoding is impressed on the signals and this subsequently permits assignment of the received signal to a volume element
Data Source
AI summary
The disclosure relates to a positioning device for positioning in a static magnetic field of a magnetic resonance tomography system and a magnetic resonance tomography system. The positioning device may be moved along a first axis in the magnetic field. Herein, the positioning device includes a plurality of magnetic-field-strength sensors arranged at a distance from one another in the direction of the first axis in predetermined positions on the positioning device.