Implanted Sensing Circuit Calibration Using In-Body Stimulus Comparison
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Solution Overview
Problem
Current calibration methods for the sensing circuitry of implanted medical devices are limited by external noise and cannot account for variations in external components, leading to improper sensitivity optimization and long calibration times, especially since they are typically performed during manufacturing and not after implantation.
Innovation Solution
A system and method that uses electrodes to deliver a calibration stimulus with a signal characteristic of interest, allowing the sensing circuitry to adjust parameters such as gain or sensitivity correction factors in real-time, accounting for all components affecting the sensing channel, including those external to the integrated circuit, and enabling continuous 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 completed before implantation, but the calibration does not account for external components and is prone to noise interference
Solution Approach 1:
The patent performs calibration during the manufacturing process using integrated circuit test equipment before the device is implanted. This preliminary calibration establishes baseline sensitivity values that are stored in non-volatile memory, allowing the device to operate with pre-calibrated sensing channels while still enabling post-implantation adjustments if needed.
Solution Approach 2:
The patent introduces an intermediary calibration process that bridges manufacturing and clinical operation. External test equipment is used during manufacturing to establish initial calibration, while the device retains the capability for post-implantation recalibration using the same external equipment, creating a continuous calibration pathway that accounts for both manufacturing constraints and clinical requirements.
2Loss of time
If calibration is performed at the integrated circuit test stage, then calibration time is reduced, but external components in the sensing circuitry are not accounted for
Solution Approach 1:
The patent performs initial calibration during manufacturing at the integrated circuit test stage, establishing baseline sensitivity values before the device is implanted. This preliminary calibration reduces the time required for clinical deployment while storing calibration data that can be refined post-implantation to account for external components.
Solution Approach 2:
The patent enables dynamic recalibration of sensing channel sensitivity both during manufacturing and after implantation. The calibration values are stored in non-volatile memory but can be updated and adjusted, allowing the system to adapt to actual performance characteristics of external components while maintaining the efficiency of initial manufacturing calibration.
3Measurement precision
If fine resolution gain adjustment is used in analog amplifiers or digital domain, then sensing sensitivity can be tuned to high accuracy, but each device requires individual trimming or calibration
Solution Approach 1:
The patent implements self-service calibration where each device automatically determines its own sensitivity characteristics during manufacturing and stores calibration values in its own non-volatile memory. The fine resolution gain adjustment capability is used, but the calibration process is automated and device-specific, eliminating the need for manual trimming while maintaining high sensing accuracy.
Solution Approach 2:
The patent utilizes parameter changes in the form of digital gain values that are automatically determined during manufacturing calibration. Instead of manual trimming, the system automatically adjusts digital domain parameters to achieve the desired sensitivity, reducing device complexity while maintaining high measurement precision through automated parameter optimization.
4Measurement precision
If small stimulus is used for calibration during manufacturing, then the sensing channel gain can be extracted, but the stimulus is prone to be corrupted by external noise sources
Solution Approach 1:
The patent performs gain measurement during manufacturing when the device is in a controlled environment with minimal external noise interference. The small stimulus approach is used to extract sensing channel gain, and the calibration values are stored for later use, effectively capturing the device characteristics before external noise becomes a factor during clinical operation.
Solution Approach 2:
The patent uses an intermediary calibration stimulus that is delivered through the integrated circuit test equipment during manufacturing. This intermediate calibration process establishes baseline gain values that are then used to correct for variations in external components, effectively mediating between the controlled manufacturing environment and the variable clinical environment.
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.