Orthogonal Coil Pair Layout for MRI Magnetic Probe Tracking
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Solution Overview
Problem
Magnetic tracking systems are compromised by metallic elements in or near the radiated space, leading to calibration errors, particularly in magnetic resonance imaging (MRI) scanners.
Innovation Solution
A frame with three pairs of separated planar conductive coils, each pair having a common axis of symmetry, is used to generate a magnetic field with a preset spatial variance and temporal rate of change, allowing for accurate tracking by a probe with a sensor that responds to these changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional magnetic transmitters are used in MRI environments, then the tracking system can operate, but metallic elements in the MRI scanner compromise the calibration and reduce measurement precision
Solution Approach 1:
The transmitter is divided into multiple independent coil pairs, each pair consisting of two coils that can be independently controlled. This segmentation allows the system to generate complex magnetic field patterns by coordinating multiple simpler units, enabling precise field control despite the presence of metallic distortions in the MRI environment.
Solution Approach 2:
Each coil pair is designed to generate a specific magnetic field gradient in a particular direction. By assigning different functional characteristics to different coil pairs (x-direction, y-direction, z-direction gradients), the system achieves precise local control over the magnetic field properties, allowing accurate tracking even when global calibration is compromised by metallic elements.
2Adaptability or versatility
If metallic elements are present in the radiated space, then the MRI scanner can function, but the magnetic field calibration is compromised and tracking precision deteriorates
Solution Approach 1:
The system changes the parameters of the magnetic field by using alternating current to drive the coil pairs, creating time-varying magnetic fields with specific spatial gradients. By modulating the frequency and amplitude of the alternating current, the system can adapt the field characteristics to compensate for metallic distortions and maintain measurement precision in the MRI environment.
Solution Approach 2:
The coil pairs are driven by alternating current that periodically reverses direction, creating oscillating magnetic fields. This periodic action allows the system to encode position information in the temporal variations of the magnetic field, enabling accurate tracking even when the static field calibration is compromised by metallic elements in the MRI scanner.
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
The solution provides precise tracking of the probe's position and orientation within the MRI environment by minimizing the impact of metallic distortions, ensuring accurate calibration and effective tracking.
Implementation Method 1
an alternating current power supply coupled to drive the separated coils of each pair in anti-phase so as to generate a magnetic field having a preset spatial variance over the volume
Implementation Method 2
a probe configured to enter the volume and having a sensor coupled to generate a signal responsive to a temporal rate of change of the magnetic field and to the preset spatial variance thereof
Data Source
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AI summary
Apparatus, having a frame encompassing a volume. The apparatus includes three pairs of separated planar conductive coils, the separated coils of each pair having a common axis of symmetry, the three pairs being attached to the frame so that the common axes of symmetry are mutually orthogonal, and so that the coils surround the volume. An alternating current power supply is coupled to drive the separated coils of each pair in anti-phase so as to generate a magnetic field having a preset spatial variance over the volume. The apparatus also includes a probe that is configured to enter the volume and that has a sensor coupled to generate a signal responsive to a temporal rate of change of the magnetic field and to the preset spatial variance thereof. A processor is configured to receive the signal and in response formulates a position of the probe within the volume.