IMD Orientation Calibration via Gravitational Vector Analysis
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Solution Overview
Problem
Implantable medical devices (IMDs) face challenges in maintaining accurate posture detection over time due to shifting or rotation within the patient's body, leading to errors in posture monitoring and therapy delivery, as the initial reference orientation becomes invalid with changes in the device's position or orientation.
Innovation Solution
The IMD automatically recalibrates its reference orientation by sensing multiple orientation vectors with respect to the gravitational field, identifying an upright vector, and classifying them to define sagittal and transverse planes, allowing it to determine its current orientation and the patient's posture, even as the device's position changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the IMD uses an initial reference orientation for posture detection, then the device can perform posture monitoring immediately after implantation, but the accuracy of posture detection deteriorates over time as the device shifts or rotates within the patient's body
Solution Approach 1:
The system performs preliminary calibration by collecting orientation vectors during an initial period after implantation when the device is still settling. These preliminary measurements are used to establish a baseline reference orientation that accounts for the device's final position within the body, enabling accurate posture detection from the start without requiring later recalibration
Solution Approach 2:
The system continuously monitors the device's orientation vectors and compares them against the established reference orientation. When deviations exceeding a threshold are detected, the system automatically triggers recalibration procedures to update the reference orientation, ensuring ongoing accuracy despite device migration or rotation over time
2Reliability
If the clinician performs manual recalibration periodically, then the posture detection accuracy can be maintained, but the complexity of device operation and the need for repeated clinical visits increase
Solution Approach 1:
The IMD performs automatic self-calibration by autonomously collecting orientation vectors, identifying gravitational direction, and updating its reference orientation without clinician intervention. The device monitors its own positional changes and triggers recalibration procedures automatically, eliminating the need for manual recalibration and reducing clinical follow-up requirements
Solution Approach 2:
The system dynamically adjusts the reference orientation parameters based on detected changes in device position or orientation. By monitoring orientation vectors and comparing them to the established baseline, the system automatically updates calibration parameters when deviations are detected, maintaining accuracy without manual intervention
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
This approach enables continuous accurate posture detection and reduces the need for manual recalibration by the clinician, ensuring reliable monitoring and therapy delivery without the accumulation of errors from shifting or rotation of the IMD.
Implementation Method 1
sensing, by one or more sensors of an implantable medical device (IMD), a plurality of orientation vectors of the IMD with respect to a gravitational field
Data Source
AI summary
Techniques are disclosed for automatically calibrating a reference orientation of an implantable medical device (IMD) within a patient. In one example, sensors of an IMD sense a plurality of orientation vectors of the IMD with respect to a gravitational field. Processing circuitry of the IMD processes the plurality of orientation vectors to identify an upright vector that corresponds to an upright posture of the patient. The processing circuitry classifies the plurality of orientation vectors with respect to the upright vector to define a sagittal plane of the patient and a transverse plane of the patient. The processing circuitry determines, based on the upright vector, the sagittal plane, and the transverse plane, a reference orientation of the IMD within the patient. As the orientation of the IMD within the patient changes over time, the processing circuitry may recalibrate its reference orientation and accurately detect a posture of the patient.