Implantable Stimulator Field Modeling Using Directional Tissue Resistance
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Solution Overview
Problem
Current implantable neurostimulator devices face challenges in accurately modeling and visualizing the stimulation field within the patient's tissue, which can lead to suboptimal therapeutic outcomes due to the assumption of homogeneous tissue resistance and lack of directional resistance data.
Innovation Solution
The implementation of a system that includes an implantable stimulator device and an external device capable of applying test currents between electrode nodes, measuring voltage data sets, and using improved field modeling algorithms to determine a three-dimensional representation of the electric field in the patient's tissue, taking into account directional resistances rather than bulk tissue resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If homogeneous tissue resistance is assumed for field modeling, then device complexity is reduced, but measurement precision and therapeutic outcome accuracy deteriorate
Solution Approach 1:
The system performs preliminary measurements of voltage data at multiple electrode nodes before finalizing the field model. This preliminary action allows the system to characterize directional resistances in advance, enabling more accurate field modeling without increasing real-time computational complexity during therapy delivery.
Solution Approach 2:
The system uses measured voltage data from multiple electrode nodes to feedback-adjust the field model. By comparing actual voltage measurements with modeled expectations, the system refines the resistance characteristics and improves field visualization accuracy iteratively.
2Ease of operation
If bulk tissue resistance is used instead of directional resistance, then ease of operation is improved, but measurement precision and therapeutic efficacy worsen
Solution Approach 1:
The system segments the tissue resistance characterization into directional components by measuring voltages at multiple electrode nodes in different orientations. This segmentation allows the system to capture anisotropic resistance properties (different resistance values in different directions) while maintaining a systematic measurement approach that remains operationally manageable.
Solution Approach 2:
The system transitions from scalar bulk tissue resistance to three-dimensional directional resistance characterization by measuring voltages at multiple spatial locations and orientations. This dimensional expansion captures the full complexity of tissue resistivity without requiring overly complex operational procedures.
3Measurement precision
If three-dimensional electric field representation is implemented, then measurement precision and therapeutic accuracy are improved, but device complexity and computational requirements worsen
Solution Approach 1:
The system uses the stimulator's own electrode nodes as both the stimulation interface and the measurement sensors. This self-service approach eliminates the need for separate measurement apparatus, reducing overall system complexity while enabling three-dimensional field characterization through existing hardware.
Solution Approach 2:
The electrode nodes serve dual functions: delivering therapeutic stimulation and measuring voltage data for field modeling. This multi-functionality reduces the number of separate components needed, thereby reducing device complexity while achieving accurate three-dimensional field representation.
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 allows for a more accurate visualization and adjustment of the electric field within the tissue, enabling better targeting of therapeutic effects and minimizing side effects by accounting for the variability in tissue resistivity, thereby improving the efficacy of neurostimulation treatments.
Implementation Method 1
first control circuitry configured to execute an algorithm configured to provide at least one test current between at least two of the electrodes nodes, and in response to the at least one test current measure a voltage data set at at least some of the plurality of electrode nodes
Data Source
AI summary
A field measurement algorithm and measuring circuitry in an implantable stimulator, and an field modelling algorithm operable in an external device, are used to determine an electric field in a patient's tissue. The field measuring algorithm provides at least one test current between two electrodes, and a plurality of voltage differentials are measured at different combinations of the electrodes. The voltage differential data is telemetered to the field modelling algorithm which determines directional resistance at different locations in the patient's tissue. The field modelling algorithm can then use a stimulation program selected for the patient and the determined directional resistances to determine voltages in the patient's tissue at various locations, which in turn can be used to model a more-accurate electric field in the tissue, and preferably to render an electric field image for display in a graphical user interface of the external device.