Magnetic Field Sensor Positioning for MRI Local Coils
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In magnetic resonance tomography units, accurately determining the position of local coils relative to the B0 field magnet, especially along the z-coordinate axis, is challenging due to restricted accessibility and the need for high precision, particularly in combined MRT-PET scans where radiation attenuation occurs.
Innovation Solution
A method using a magnetic field strength sensor to ascertain a characteristic magnetic field strength Bref, which is essentially equal across various x-y coordinate pairs for a given z-coordinate, allowing precise determination of the z-coordinate by moving the device along the z-axis until the sensor measures this strength within a predetermined tolerance, thereby establishing a reference point for subsequent movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the local coil is positioned close to the patient body to improve signal-to-noise ratio, then the coil position is not firmly defined and requires separate recording, but the accessibility for position determination is restricted and precision is compromised
Solution Approach 1:
A magnetic field strength sensor serves as an intermediary device to indirectly determine the z-coordinate of the local coil. Instead of directly measuring the coil position, the sensor measures the magnetic field strength at the coil location, which correlates to the z-coordinate through pre-acquired reference data. This intermediary measurement approach enables precise position determination despite restricted accessibility.
Solution Approach 2:
The patent replaces direct mechanical position measurement with magnetic field-based measurement. By using a magnetic field strength sensor to measure the magnetic field characteristics and correlating these measurements with pre-acquired reference data, the system substitutes mechanical positioning methods with a magnetic field-based determination method, achieving higher precision in confined spaces.
2Loss of information
If optical projection methods are used to determine local coil position, then position information can be obtained, but the method is difficult to implement in the scanning area due to restricted accessibility and potential coverage by heated blankets
Solution Approach 1:
The patent substitutes optical projection methods with magnetic field-based measurement. The magnetic field penetrates through heated blankets and other coverings that block optical methods, enabling position determination in the scanning area without being affected by restricted accessibility or coverage by heated blankets.
Solution Approach 2:
The patent changes the measurement parameter from optical projection to magnetic field strength measurement. Magnetic fields can penetrate through heated blankets and other materials that block light, allowing position information acquisition in conditions where optical methods fail.
3Measurement precision
In combined MRT-PET scans, if the local coil position is not precisely recorded, then radiation attenuation effects cannot be properly compensated, but achieving high precision position recording is challenging due to the complex environment
Solution Approach 1:
The patent performs preliminary acquisition of reference magnetic field strength data at multiple known z-positions before actual position determination. This pre-acquired reference data creates a mapping between magnetic field strength and z-coordinate, enabling precise position determination during scanning without requiring complex real-time calculations or additional hardware complexity.
Solution Approach 2:
The magnetic field strength measurement serves as an intermediary that simplifies the position determination process. Instead of directly tracking the coil position through complex mechanical or optical systems, the patent uses magnetic field strength as an intermediate parameter that can be easily measured and correlated to z-coordinate through reference data, reducing system complexity while maintaining high precision.
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 method enables precise positioning of local coils and shim coils relative to the B0 field magnet, improving signal-to-noise ratio and compensating for radiation attenuation effects in MRT-PET scans by accurately defining their z-coordinate and orientation, thus enhancing imaging accuracy.
Implementation Method 1
a magnetic field strength sensor (60) attached to the device (50) in a fixed relative position. In an act of the method, a characteristic magnetic field strength Bref of the B0 field magnet (11) is ascertained
Data Source
AI summary
A method for determining a position of a mobile device relative to a B0 field magnet along a z-coordinate axis, and a device and a magnetic resonance tomography unit for performing the method are provided. The device includes a magnetic field strength sensor arranged in a fixed relative position. A characteristic magnetic field strength Bref of the B0 field magnet that emerges for a plurality of x-y coordinate pairs with a same reference z-coordinate zref is ascertained. The device is moved along the z-coordinate axis until the magnetic field strength sensor measures the characteristic magnetic field strength Bref.