Implanted Sensing Circuit Calibration Using In-Body Stimulus Signals
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Solution Overview
Problem
Current calibration methods for sensing channels in implantable medical devices (IMDs) are inadequate as they do not account for external components, leading to improper calibration due to noise interference and require lengthy test times, limiting sensitivity optimization.
Innovation Solution
A system and method that utilizes electrodes to deliver a stimulus with known characteristics, allowing for in-body calibration of sensing circuitry by comparing the stimulus signal with sensed signals to adjust parameters such as gain and sensitivity, accounting for all components affecting sensitivity, and enabling real-time calibration post-implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration is performed during manufacturing using external test equipment, then calibration can be done before implantation, but the calibration does not account for external components and is prone to noise interference
Solution Approach 1:
The patent performs calibration after implantation rather than during manufacturing, allowing the system to account for all actual components including external components that affect sensing. The IMD autonomously generates test signals and performs calibration without external equipment, eliminating noise interference from external test equipment.
Solution Approach 2:
The IMD performs self-calibration using its own sensing circuitry and signal generation capabilities. The device generates test signals through its pulse generator, senses these signals through its sensing circuitry, and autonomously determines calibration factors without requiring external test equipment or manual intervention.
2Loss of time
If calibration is performed during manufacturing, then calibration time can be reduced, but external components affecting sensitivity are not accounted for
Solution Approach 1:
The system performs calibration after implantation when all components are in their final positions, ensuring that external components affecting sensitivity are accounted for. The calibration process includes measuring actual signal characteristics through the complete signal path from pulse generator through sensing circuitry.
Solution Approach 2:
The patent determines calibration factors by comparing expected signal parameters with actual measured parameters. The system adjusts sensitivity parameters based on the ratio of expected to actual signal characteristics, accounting for all components in the final implanted configuration.
3Measurement precision
If fine gain adjustment steps are used, then sensitivity can be tuned to high accuracy, but calibration complexity increases
Solution Approach 1:
The IMD autonomously performs calibration by generating test signals, sensing them, and automatically calculating calibration factors. The system compares expected signal characteristics with actual measurements and adjusts gain parameters without requiring complex external calibration equipment or manual procedures.
Solution Approach 2:
The system uses feedback from actual signal measurements to determine appropriate calibration factors. By comparing expected signal parameters with measured parameters, the IMD automatically adjusts sensitivity settings to achieve accurate calibration without complex external intervention.
Data Source
AI summary
A system is provided that includes electrodes configured to be implanted in a body, and a pulse generator (PG) circuitry to deliver a stimulus to one or more of the electrodes. The system also includes sensing circuitry configured to define a sensing channel between one or more of the electrodes to sense signals indicative of a physiologic activity of interest, and the sensing circuitry further configured to collect a calibration signal over the sensing channel. The sensing circuitry and PG circuitry are housed within an implantable medical device (IMD). The system also includes one or more processors configured to determine a signal characteristic of interest (COI) of the calibration signal. The one or more processors are also configured to compare a signal COI of the stimulus to the signal COI of the calibration signal, and adjust a parameter of the sensing circuitry or PG circuitry based on the comparison.