Susceptibility Probe Coil Taring for Accurate Surgical Marker Detection
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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 in sense coils from drive coils, which are exacerbated by manufacturing tolerances and small probe diameters, leading to interference and reduced accuracy.
Innovation Solution
The probe design incorporates at least two first coils and one second coil arranged as a gradiometer, with the coils connected in anti-series or opposite directions to minimize baseline voltage, and a baseline voltage taring device with an elongate conductor generating a balancing magnetic field to offset residual voltages, ensuring the sense voltage is predominantly from the marker response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a coil arrangement is used to cancel voltages induced from drive coils, then measurement precision is improved, but device complexity increases due to additional coils and connection arrangements
Solution Approach 1:
A compensation coil is introduced as an intermediary element between the drive coil and sense coil. This compensation coil generates a magnetic field that specifically counteracts the spurious voltages induced in the sense coil by the drive coil, thereby isolating the sense coil from harmful electromagnetic interference while maintaining the necessary measurement function.
Solution Approach 2:
The invention modifies the magnetic field parameters by introducing a compensation coil with specific winding directions and current characteristics. The compensation coil's magnetic field is designed to be equal and opposite to the spurious field at the sense coil location, changing the net magnetic field parameters to eliminate unwanted voltage induction while preserving the drive field's useful function.
2Ease of operation
If probe diameter is reduced to minimize surgical incision size, then ease of operation is improved, but manufacturing precision becomes more difficult to achieve due to amplified voltage changes from small coil position variations
Solution Approach 1:
The invention converts the harmful sensitivity to coil position variations into a beneficial feature. By using the compensation coil to actively cancel spurious voltages, the system can operate with smaller probe diameters without suffering from amplified measurement errors. The compensation mechanism turns the previously problematic sensitivity into a controlled, compensatable effect, enabling miniaturization while maintaining precision.
3Power
If drive current is increased to improve signal strength, then power is improved, but object-generated harmful factors increase due to larger voltages induced in sense coils from drive coils
Solution Approach 1:
The compensation coil acts as an anti-weight or counterweight to the harmful electromagnetic effects. It generates a magnetic field that is equal and opposite to the spurious field induced by the drive coil, effectively balancing out the harmful voltage induction. This allows the drive current to be increased for stronger signals while the compensation coil simultaneously counteracts the increased spurious voltages.
Solution Approach 2:
The invention converts the harmful voltage induction from the drive coil into a beneficial compensation mechanism. The compensation coil uses the same drive current to generate a counter-field that cancels the spurious voltages, turning the harmful effect into a useful cancellation mechanism that enables higher power operation without interference.
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 design enhances the accuracy of marker position determination by minimizing baseline voltage interference, allowing for precise localization of magnetic markers even with smaller probe diameters, thus improving surgical precision.
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 which comprises a first elongate conductor defining a conducting path extending partially around the probe axis... adapted for connection to a current source to generate a balancing magnetic field in the vicinity of the one or more sense coils
Data Source
Figure 1~2
Figure 3~4
Figure 5
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.