Biopotential Current Measurement Circuit for EMI-Resistant Sensing
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Solution Overview
Problem
Biopotential measurements in medical procedures are susceptible to electromagnetic interference (EMI), leading to degraded signal quality and noise, particularly in clinical environments where devices like electrosurgical instruments and microwave ablation units are used, and existing solutions are complex and not suitable for portable applications.
Innovation Solution
A novel biopotential measurement system that measures current rather than voltage, using high resistance resistors and amplifiers to isolate the measurement subject from electrical ground, thereby reducing common mode signals and interference, and employing a current detection method to improve signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional voltage measurement methods are used in clinical environments, then biopotential signals can be obtained, but electromagnetic interference from devices like electrosurgical instruments and microwave ablation units degrades signal quality and increases noise
Solution Approach 1:
The patent replaces conventional voltage measurement methods with a current measurement method. By measuring current through high resistance resistors connected to electrodes, the system achieves immunity to electromagnetic interference while maintaining the ability to detect biopotential signals. This substitution of measurement methodology fundamentally resolves the vulnerability to EMI in clinical environments.
Solution Approach 2:
The patent introduces high resistance resistors as intermediary elements between the electrodes and the measurement circuit. These resistors serve as mediators that convert the measured quantity from voltage to current, thereby isolating the measurement system from electromagnetic interference while still allowing detection of the underlying biopotential signals through the current they generate.
2Measurement precision
If existing EMI mitigation techniques are implemented, then signal-to-noise ratio improves, but system complexity increases making them unsuitable for portable applications
Solution Approach 1:
The patent replaces complex active EMI mitigation circuits with a passive current measurement approach. By fundamentally changing from voltage to current measurement, the system achieves superior signal-to-noise ratio without requiring complex filtering, shielding, or active cancellation circuits, thereby enabling portable implementations.
Solution Approach 2:
The patent employs simple, passive high resistance resistors as the core EMI mitigation element. These inexpensive, passive components provide robust EMI rejection without the complexity, power consumption, or cost of active mitigation systems, making the overall system suitable for portable and potentially disposable applications.
3Adaptability or versatility
If lead wire extension cables are used to reach from patient to ECG device, then connectivity is achieved, but susceptibility to RFI is exacerbated
Solution Approach 1:
The patent replaces voltage measurement with current measurement, which fundamentally changes the system's susceptibility to interference. Current measurement through high resistance resistors is inherently more immune to RFI than voltage measurement, allowing the use of extension cables without exacerbating interference problems.
Solution Approach 2:
The patent converts the potential harm of long lead wires into a benefit by using current measurement. The high resistance resistors ensure that even with extended cable lengths, the current measurement remains stable and immune to RFI, turning what would normally be a vulnerability into an advantage for flexible patient positioning.
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 provides robust, portable, low-power biopotential measurements with improved signal quality, reduced noise, and the ability to measure electrode impedance, making it suitable for various medical applications while being immune to external electrical and magnetic fields.
Implementation Method 1
using high resistance resistors and amplifiers to isolate the measurement subject from electrical ground, thereby reducing common mode signals and interference
Implementation Method 2
A novel biopotential measurement system that measures current rather than voltage, using high resistance resistors and amplifiers
Data Source
AI summary
System and apparatus for measuring biopotential and implementation thereof. A device for mitigating electromagnetic interference (EMI) thereby increasing signal-to-noise ratio is disclosed. Specifically, the present disclosure relates to an elegant, novel circuit for measuring a plurality of biopotentials in useful in a variety of medical applications. This allows for robust, portable, low-power, higher S/N devices which have historically required a much bigger footprint.