Surgical Marker Susceptibility Probe With Phase-Stable Coil Balancing
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Solution Overview
Problem
Existing susceptibility probes for detecting magnetic markers suffer from phase flips in sense voltage due to varying magnetic flux when moving axially relative to the marker, leading to inaccurate positioning, and require large probe diameters or reduced sensitivity when attempting to minimize these effects.
Innovation Solution
A probe design with a first set of coils, including a sense coil between a pair of drive coils connected in series, and a balancing element axially separated from the coils, which offsets sense voltage induced by the drive coils, allowing for a single phase change in sense voltage as the probe moves axially.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long drive coil is used to generate a strong magnetic drive field, then probe sensitivity is improved and marker detection distance is increased, but magnetic flux variation increases causing phase flips in sense voltage
Solution Approach 1:
The drive coil is divided into two separate drive coils (first drive coil and second drive coil) positioned at different locations along the probe. This segmentation reduces the magnetic flux variation at any single location while maintaining the overall detection sensitivity through the combined effect of multiple coils.
Solution Approach 2:
A balancing coil is introduced as an intermediary element that generates a compensating magnetic field to offset the flux variations produced by the drive coils. This balancing coil acts as a mediator that stabilizes the sense voltage by counteracting the harmful magnetic flux reversals.
2Reliability
If the probe housing diameter is increased to contain side lobes, then phase flips are avoided, but surgical incision size increases
Solution Approach 1:
By segmenting the drive coil into multiple smaller coils, the side lobes are contained within smaller regions that fit within the original probe housing dimensions, eliminating the need to increase probe diameter.
Solution Approach 2:
The balancing coil serves as a mediator that actively suppresses side lobe formation through compensating magnetic fields, allowing the probe to maintain a compact size while preventing phase flips.
3Reliability
If drive coil length is reduced to minimize side lobes, then phase flips are reduced, but magnetic drive field magnitude decreases
Solution Approach 1:
Multiple drive coils are combined to produce a cumulative magnetic drive field that equals or exceeds the strength of a single long drive coil, while each individual coil maintains shorter length to reduce side lobes and phase flips.
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 design maintains high sensitivity and reduces phase flips, enabling accurate marker positioning without increasing probe diameter, thus suitable for surgical applications.
Implementation Method 1
An AC current may be supplied to a drive coil, thereby generating a magnetic drive field. The magnetic drive field induces a response from the magnetic marker
Implementation Method 2
The magnetic drive field induces a response from the magnetic marker, which, in turn, induces a sense voltage in the sense coil
Data Source
AI summary
A probe (303; 403) for sensing a magnetic marker, comprising a first set of coils (313; 413), which comprises a first coil of a first coil type, e.g. a sense coil (305; 405), disposed between a first pair of coils of second coil type, e.g. drive coils (301a, 301b; 401a, 401b), that are connected in series, and a balancing element (317; 417) which is axially separated from the first set of coils (313; 413) along a length of the probe (303; 403). The balancing element (317; 417) is configured and arranged to generate a sense voltage that wholly offsets, partially offsets, or minimises, a sense voltage induced in the sense coil or coils (305; 405) of the first set of coils from the drive coils or coil (301a, 301b; 401a, 401b). Also disclosed is a detection system comprising a probe (303; 403), a magnetic field generator arranged to drive an alternating magnetic field through the drive coils (301a, 301b; 401a, 401b) of the first set of coils and the balancing element (317; 417), and at least one detector arranged to receive a signal indicative of a sense voltage.