Magnetic Field Sensor Compensation Circuit for MRI Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current magnetic field sensors used in MRI apparatuses are blinded by strong static magnetic fields, making it impossible to accurately measure and compensate for magnetic noise fields, which affects image quality and diagnostic capabilities.
Innovation Solution
A magnetic field sensor system that includes a resistive sensor and field compensation coils assembly, with a compensation circuit to generate a magnetic field that compensates for the static magnetic field at the sensor position, allowing for accurate measurement of magnetic noise fields even in the presence of stronger static fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic field sensor is placed in an MRI apparatus to measure magnetic noise fields, then the sensor can be positioned close to the imaging cavity for effective noise compensation, but the strong static magnetic field from the MRI apparatus will blind or saturate the sensor, making it impossible to accurately measure the noise fields
Solution Approach 1:
The patent divides the magnetic field measurement task into two separate sensing systems: one for measuring the strong static magnetic field (using a first type of sensor capable of operating in high field conditions) and another for measuring the weaker AC noise fields (using a second type of sensor that would be blinded by the static field alone). This segmentation allows each sensor to be optimized for its specific measurement task without interference from the other field components.
Solution Approach 2:
The patent introduces magnetic field shielding structures and compensation coils as intermediary elements. The shielding structures selectively block or redirect the static magnetic field away from the noise field sensor, while allowing AC noise fields to pass through. Compensation coils generate opposing magnetic fields to cancel out the static field effect at the sensor location, enabling accurate noise field measurement in the presence of strong static fields.
2Reliability
If the sensor is placed farther from the MRI apparatus to avoid static field saturation, then the sensor can operate without blinding, but the measurement accuracy of magnetic noise fields deteriorates due to increased distance from the noise source
Solution Approach 1:
The patent employs separate sensor systems positioned at different locations: one sensor system is placed close to the MRI apparatus for accurate noise field detection, while another sensor system is placed farther away in a region with lower static field intensity. The systems are coordinated to provide complementary measurements, allowing the close sensor to capture noise field characteristics while the distant sensor operates in a more favorable magnetic environment.
Solution Approach 2:
Magnetic shielding structures are positioned between the sensor and the MRI apparatus to create a controlled magnetic environment. These shields selectively attenuate the static magnetic field while permitting AC noise fields to reach the sensor, enabling the sensor to be placed closer to the noise source without suffering from static field saturation.
3Device complexity
If a single magnetic field sensor is used to measure both static and AC magnetic fields, then the device complexity is reduced, but the measurement precision deteriorates because the sensor cannot distinguish between the two field types when both are present
Solution Approach 1:
The patent implements separate dedicated sensor systems for measuring static magnetic fields and AC noise fields. The first sensor system is optimized for DC/static field measurement with high range and stability, while the second sensor system is optimized for AC/noise field measurement with high sensitivity and bandwidth. This functional segmentation eliminates cross-interference and allows each sensor to be tuned to its optimal operating characteristics.
Solution Approach 2:
The patent employs dynamic field separation techniques where compensation coils actively generate time-varying magnetic fields to cancel out the static field component at the noise sensor location. The system dynamically adjusts the compensation field strength and polarity based on real-time measurements, enabling the noise sensor to selectively respond only to AC variations while ignoring the static background field.
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
Enables effective compensation of magnetic noise fields within the MRI apparatus, improving image quality and diagnostic accuracy by avoiding sensor saturation and allowing for precise measurement of noise fields.
Implementation Method 1
field compensation coils assembly, with a compensation circuit to generate a magnetic field that compensates for the static magnetic field at the sensor position
Implementation Method 2
A magnetic field sensor system that includes a resistive sensor
Data Source
AI summary
Magnetic field sensor, in particular for measuring magnetic noise fields caused by environmental magnetic noise in combination with MRI apparatus, the magnetic field sensor being further provided with field compensation coils assembly and with a compensation circuit driving the field compensation coils assembly to generate a magnetic field compensating the static magnetic field dissipating outside from the static magnetic field generator or from the gantry of the MRI apparatus at the position of the magnetic sensor. A method for operating the magnetic field sensor and a method and a system for compensation magnetic noise caused by environmental noise are also provided. An MRI apparatus is also disclosed comprising such a system and carrying out such a method for compensating magnetic noise fields.