Implantable Lead Leakage Detection via Differential Amplification
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Solution Overview
Problem
Implantable medical leads experience signal leakage due to insulation deterioration and bodily fluid ingress, which can lead to faulty therapy as impedance tests fail to detect leakage, causing adverse effects on neurological signal sensing.
Innovation Solution
A method and system that utilize a stimulation signal below tissue activation threshold from one conduction path and sense it using two other conduction paths connected to a sensing circuit, such as a differential amplifier, to detect amplitude imbalances indicative of leakage between conduction paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impedance testing is used to detect conduction path integrity, then the testing method is simple and widely applicable, but leakage between conduction paths cannot be detected when leakage impedance is within normal range
Solution Approach 1:
The detection method segments the conduction path testing into multiple independent sensing channels. By using two separate sensing conduction paths instead of a single path, the system can compare signals to detect leakage. This segmentation allows the detection of leakage between specific conduction paths while maintaining overall system reliability.
Solution Approach 2:
The invention changes the detection parameter from impedance measurement to signal amplitude comparison. By providing a stimulation signal below tissue activation threshold and comparing the amplitudes of sensed signals on different conduction paths, the system can detect leakage that would be invisible to traditional impedance testing. This parameter change enables detection of leakage with impedance within normal ranges.
2Measurement precision
If stimulation signal level is increased to improve signal detection, then sensing capability improves, but tissue activation may occur causing adverse effects
Solution Approach 1:
The system uses a stimulation signal that is partial in strength—specifically, a level below the tissue activation threshold. This partial action approach allows the signal to be sufficiently strong for detection purposes while remaining sub-threshold to avoid causing tissue activation or adverse effects. The differential amplification compensates for the lower signal strength.
Solution Approach 2:
The invention introduces a differential amplifier as an intermediary device between the sensing electrodes and the detection system. This intermediary amplifies the small sensed signals from the conduction paths, enabling precise detection without requiring high stimulation levels that would cause tissue activation. The differential amplifier mediates between the weak sensed signals and the detection requirements.
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
Effectively detects signal leakage between conduction paths, preventing adverse therapy effects by identifying imbalances in sensed signal amplitudes, allowing for timely intervention and adjustment of therapy.
Implementation Method 1
the sensing circuit may include a differential amplifier that receives the signals on the two sensing conduction paths as the inputs. When leakage is present between one of the sensing conduction paths and the stimulation conduction path, the imbalance that occurs on the two sensing paths presents a relatively high differential at the inputs of the differential amplifier.
Data Source
AI summary
Leakage of signal between conduction paths of an implantable medical lead or lead and lead extension combination is detected. A stimulation signal is provided via one electrode. Two other electrodes sense the stimulation signal. A difference in amplitude of the two sensed signals is determined and based on this difference, leakage is detected. A sensing circuit may use differential amplification of the two signals and compare a resulting output signal to a leakage threshold. When the amplitude of the output signal exceeds the leakage threshold, then leakage is occurring between the conduction path providing the stimulation and one of the conduction paths used for sensing. Other techniques for determining leakage from the difference may also be used such as comparing the amplitudes of the two sensed signals and providing a value that is based on the comparison to indicate whether leakage is present.