Susceptibility Probe Taring for Accurate Surgical Marker Localization
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Solution Overview
Problem
Existing susceptibility probes for detecting implanted magnetic markers in surgery face challenges in accurately determining marker position due to residual baseline voltages induced by manufacturing tolerances and coil positioning inaccuracies, especially in smaller probes, which interfere with the sense voltage and hinder precise localization.
Innovation Solution
The probe design incorporates at least two first coils and one second coil arranged as a gradiometer, with a baseline voltage taring device comprising an elongate conductor generating a balancing magnetic field to offset residual baseline voltages, allowing for accurate determination of marker proximity by minimizing interference from drive coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a smaller probe diameter is used to reduce surgical incision size, then the invasiveness of the procedure is reduced, but the accuracy of marker localization deteriorates due to larger relative changes in drive field and sensed voltage from small positioning variations
Solution Approach 1:
A baseline voltage taring device is introduced as an intermediary component to compensate for the residual baseline voltage caused by manufacturing tolerances and positioning variations. This device generates a counter-voltage that cancels out the unwanted baseline signal, thereby improving measurement accuracy without requiring larger probe dimensions
Solution Approach 2:
The patent adjusts electrical parameters by introducing a taring voltage that can be tuned to match and cancel the residual baseline voltage. By changing the electrical compensation parameter (taring voltage magnitude and phase), the system maintains accurate marker localization despite physical dimension constraints
2Measurement precision
If coil positioning precision is improved to reduce residual baseline voltage, then the accuracy of marker detection is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The system incorporates a feedback mechanism where the residual baseline voltage is measured and then compensated by the taring device. This closed-loop approach allows the system to automatically correct for manufacturing variations without requiring extremely tight manufacturing tolerances
Solution Approach 2:
The baseline voltage taring device serves as a mediator that decouples the relationship between manufacturing precision and measurement accuracy. It absorbs the impact of manufacturing variations, allowing standard manufacturing tolerances to be used while still achieving high measurement precision
3Reliability
If drive coil strength is increased to improve marker detection sensitivity, then the detection capability is improved, but the residual baseline voltage induced in sense coils increases, reducing measurement accuracy
Solution Approach 1:
The patent converts the harmful effect of strong drive coils (which generate large baseline voltages) into a beneficial situation by using the taring device to measure and cancel the baseline voltage. The stronger drive coils that would normally be problematic now enable better signal-to-noise ratio, with the baseline simply being compensated electronically
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 configuration enables more precise localization of magnetic markers by ensuring that sense voltages are predominantly attributed to the response field, thereby improving the accuracy of surgical procedures with smaller probe diameters.
Implementation Method 1
A current is supplied to a drive coil, thereby generating a driving magnetic field. The driving magnetic field induces a response from the magnetic marker
Implementation Method 2
The driving magnetic field induces a response from the magnetic marker, which, in turn, induces a sense voltage in a sense coil
Implementation Method 3
a baseline voltage taring device comprising an elongate conductor generating a balancing magnetic field to offset residual baseline voltages
Data Source
AI summary
A probe for locating a magnetic marker for use in surgery. The probe comprises at least two first coils (3a, 3b) and at least one second coil (5) which are arranged substantially coaxially on a longitudinal axis of the probe for measuring the proximity of a magnetic marker to the probe, and a baseline voltage taring device (7) comprising a first elongate conductor which defines a conducting path extending partially around the probe axis. The conducting path is configured and arranged such that in use the balancing magnetic field induces a balancing voltage in a sense coil that at least partially offsets the baseline voltage. Also disclosed is a method of manufacturing such a probe, a method of setting up such a probe for use in sensing a magnetic marker, and detection apparatus for locating a magnetic marker during surgery.