Harmonic Magnetic Marker Detection for Surgical Signal Interference
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Solution Overview
Problem
Existing magnetic detection systems struggle to accurately distinguish between magnetic markers and tracers, particularly in the presence of metallic tools, human tissue, and other magnetically responsive materials, leading to interference and inaccurate localization during surgical procedures.
Innovation Solution
A detection system utilizing a non-linear magnetic marker with a large Barkhausen discontinuity and a harmonic filter to generate a pure single-frequency sinusoidal waveform, combined with a harmonic detection circuit to isolate the marker's response from spurious signals, allowing for accurate localization and quantification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic detection system uses a handheld probe to detect magnetic markers during surgery, then the marker can be localized, but the probe cannot distinguish the marker from other magnetically responsive materials such as tracers, metallic tools, and human tissue
Solution Approach 1:
The system applies periodic alternating magnetic field excitation at a specific fundamental frequency to the marker. The marker responds with harmonic frequencies that are integer multiples of the fundamental frequency. By detecting and analyzing these harmonic frequencies, the system can distinguish the marker's response from other magnetic materials that do not exhibit the same harmonic frequency pattern, thereby resolving the interference problem while maintaining accurate localization.
2Reliability
If a magnetic marker with high magnetic susceptibility is used to improve detection sensitivity, then the marker can be detected at greater distances, but the marker's signal cannot be distinguished from signals generated by metallic surgical tools
Solution Approach 1:
The system uses periodic alternating magnetic field excitation at a fundamental frequency and detects the marker's response at harmonic frequencies (integer multiples of the fundamental frequency). Metallic surgical tools respond to the fundamental frequency but do not generate the same harmonic frequency pattern as the magnetic marker. This frequency-based discrimination allows the system to maintain high detection sensitivity while filtering out interference from metallic tools.
3Measurement precision
If a liquid marker containing radioisotope is used for sentinel lymph node detection, then the lymph nodes can be identified for excision, but the radioisotope has short half-life requiring injection close to surgery time
Solution Approach 1:
The system uses super-paramagnetic iron oxide nanoparticles as a magnetic tracer that can be injected days or weeks before surgery. Unlike radioisotopes with short half-lives, these nanoparticles have no half-life and remain stable in the body. The magnetic detection system can identify the tracer in sentinel lymph nodes at the time of surgery, providing both scheduling flexibility and accurate lymph node identification.
4Adaptability or versatility
If a magnetic probe detects both magnetic markers and iron oxide nanoparticle suspension, then both can be detected, but the detection system cannot distinguish the lesion marker from other magnetically responsive materials
Solution Approach 1:
The system applies periodic alternating magnetic field excitation at a fundamental frequency and detects responses at harmonic frequencies. The magnetic marker (containing bistable material) exhibits a non-linear magnetic response that generates harmonic frequencies, while the iron oxide nanoparticle suspension responds linearly at the fundamental frequency only. By analyzing the frequency spectrum and detecting harmonic components, the system can distinguish the magnetic marker from the nanoparticle suspension, maintaining both detection versatility and differentiation accuracy.
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 system effectively distinguishes between magnetic markers and tracers, providing precise localization and quantification, reducing excess tissue removal and improving surgical accuracy by minimizing interference from human tissue and other materials.
Implementation Method 1
A handheld probe generates an alternating field which excites a magnetically responsive marker, and detects the responding magnetic field.
Implementation Method 2
A detection system utilizing a non-linear magnetic marker with a large Barkhausen discontinuity and a harmonic filter to generate a pure single-frequency sinusoidal waveform
Implementation Method 3
A further approach is to use a suspension of super-paramagnetic iron oxide nanoparticles. These particles have no half-life which means that they can be available in any hospital and can be injected a number of days before surgery, making scheduling more convenient.
Data Source
Figure 1A~1B
Figure 1C~1E
Figure 2
AI summary
A method for detecting a magnetic marker comprises generating a driving magnetic field comprising first and second frequencies and detecting a response magnetic field comprising first and second response components. The magnetic marker provides a non-linear response to the driving signal. A primary portion of the response components is generated by the magnetic marker, and a secondary portion of the response components is generated by a secondary magnetic source. The method comprises determining a driving factor representing a ratio of the frequencies in the driving signal; determining a correction factor corresponding to the secondary portion of the second response component, based on the first response component and the driving factor; determining a detection signal corresponding to the primary portion of the second response component, based on the second response component and the determined correction factor; and generating an output signal based on a strength of the detection signal.