Electromagnetic Catheter Positioning via Wireless Induction
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Solution Overview
Problem
Current medical device positioning systems, such as those using electromagnetic fields, face challenges with accuracy and interference, particularly with smaller diameter catheters and the depth of placement, due to the need for heavy wires and small magnet signals, which limit their effectiveness in reducing radiation exposure and maintaining a sterile field.
Innovation Solution
The system employs an array of drive coil sets with a moveable sensor coil, using a digital signal processor and software architecture to determine the z-axis location accurately by measuring responses from x, y, and z-axis coils, and employing a quadruplet drive coil structure to enhance magnetic field generation and reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC driven coil in catheter tip is used with external sensor coils, then electromagnetic signal can be generated for location, but heavy or thick wires are needed to carry drive current which precludes use with smaller diameter catheters
Solution Approach 1:
The patent replaces the mechanical wire-based current delivery system with a wireless electromagnetic power transfer system. An external AC driven coil generates an electromagnetic field that induces current in the catheter tip coil, eliminating the need for heavy wires running through the catheter. This allows use of smaller diameter catheters while maintaining the ability to generate sufficient electromagnetic signals for accurate location tracking.
Solution Approach 2:
The system uses AC driven coils that are periodically activated in a scanning sequence rather than continuous operation. Multiple external coils are driven alternately, and the catheter tip coil responds to each in turn. This periodic activation reduces the current requirements and allows for smaller catheter diameter while maintaining measurement precision through temporal sampling of the electromagnetic responses.
2Measurement precision
If fixed magnet on catheter tip is used with external sensor coils, then location can be indicated, but magnet generates very small signal and field drops off quickly over distance limiting depth sensing
Solution Approach 1:
Instead of placing the active electromagnetic source on the catheter tip and having external sensors detect it, the patent inverts the configuration: external AC driven coils become the active sources, and the catheter tip contains a passive coil that responds to these external fields. This inversion allows for stronger signal generation at the external coils and better depth penetration, as the external coils can be positioned close to the patient's skin surface while still sensing deep internal structures.
3Measurement precision
If DC magnet system is used on catheter tip, then location can be determined, but additional charge is put into patient and other magnetic fields create significant interference
Solution Approach 1:
The system employs periodic AC driving of external coils at specific frequencies rather than static DC magnetism. By driving the external coils in a time-varying manner and using synchronous detection, the system can distinguish the catheter's electromagnetic response from other ambient magnetic fields and interference. The periodic nature allows for frequency-based filtering and signal extraction that is insensitive to DC offsets and low-frequency interference.
Solution Approach 2:
The patent changes the operational parameters from static DC magnetism to dynamic AC electromagnetic fields at controlled frequencies. By operating at specific AC frequencies and using phase-sensitive detection, the system achieves location determination while being immune to DC magnetic interference and minimizing patient charging effects. The frequency parameter is used as a discrimination tool to separate the desired signal from interference.
4Measurement precision
If x-ray or fluoroscopy is used to indicate catheter location, then reliable location indication is achieved, but patient and caregiver are exposed to undesirable amounts of radiation
Solution Approach 1:
The patent replaces the ionizing radiation-based x-ray and fluoroscopy systems with a non-ionizing electromagnetic field-based location system. External AC driven coils generate magnetic fields that induce responses in the catheter tip, and these responses are detected and processed to determine catheter location. This substitution eliminates radiation exposure to patients and caregivers while providing continuous, real-time location tracking through safe electromagnetic interactions.
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 provides more accurate and certain placement of medical devices, especially in three-dimensional space, reducing the need for radiation and maintaining a sterile field, while improving the accuracy of z-axis determination and overall system reliability.
Implementation Method 1
an array of drive coil sets, each set having two or three dimensionally oriented drive coils; a moveable sensor coil being electromagnetically communicative with the array of drive coil sets
Implementation Method 2
measuring responses from x, y, and z-axis coils, and employing a quadruplet drive coil structure to enhance magnetic field generation and reduce interference
Data Source
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AI summary
Methods, devices and systems for three-dimensional location of the disposition of a sensor coil in a subject including are disclosed. The systems include an array of three or more triplet or quadruplet drive coil sets, at least one moveable sensor coil configured to be disposed in a subject and to provide one or more sensor coil response signals responsive to the respective electromagnetic wave fields, a receiving component configured to control drive signals to the array of drive coil sets and to measure sensor coil response signals from the moveable sensor coil, and a processor is configured to determine a sensor coil disposition in the subject relative to said triplet or quadruplet drive coil sets. The receiving component provides a modified drive signal to maximize or optimize the generated respective electromagnetic wave fields, or the one or more sensor coil response signals.