Impedance Loss Model Calibration for Electrosurgical Power Control
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Solution Overview
Problem
Electrosurgical generators face inaccuracies in power control due to RF impedance losses in transmission lines, leading to improper tissue heating during surgical procedures, which current methods attempt to mitigate with complex and costly hardware for phase sampling.
Innovation Solution
The method calibrates impedance loss models using simple equations and low-cost hardware, predicting phase values based on fixed reactance in transmission lines, allowing for accurate voltage and current measurements at the tissue site by calculating source and leakage impedance parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase sampling is performed to accurately measure voltage and current, then measurement precision is improved, but device complexity increases due to requirements for high-speed hardware and greater computational complexity
Solution Approach 1:
The patent replaces expensive, complex high-speed hardware with inexpensive, commonly available microprocessors, FPGAs, or DSPs that can be implemented using standard components. The solution uses affordable computational resources to achieve the same measurement accuracy without requiring specialized expensive equipment.
Solution Approach 2:
The patent substitutes complex hardware-based phase sampling mechanisms with a software/mathematical approach. Instead of using complex physical hardware to directly measure phase, the invention uses mathematical relationships between impedance magnitude and phase to compute the required values through calibration procedures and equations.
2Manufacturing precision
If RF impedance losses are not compensated, then device complexity is reduced, but manufacturing precision deteriorates due to inaccurate power control and improper tissue heating
Solution Approach 1:
The patent performs calibration procedures in advance to determine the relationship between impedance magnitude and phase for the specific transmission line. This preliminary action stores calibration data that can be used during operation to compensate for impedance losses without requiring complex real-time measurement systems.
Solution Approach 2:
The patent introduces an impedance loss model as an intermediary between the measured impedance and the actual tissue parameters. This model, calibrated in advance, acts as a mediator that translates measured values into accurate tissue power and temperature estimates while accounting for transmission line losses.
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 provides accurate power control and tissue heating by compensating for impedance losses, ensuring precise electrosurgical energy delivery with reduced computational complexity and hardware costs.
Implementation Method 1
The tissue's impedance converts the electrical energy (also referred to as electrosurgical energy) associated with the alternating current into heat, which causes the tissue temperature to rise.
Data Source
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AI summary
Calibrating parameters of a transmission line coupled to an electrosurgical device, comprising: applying electrosurgical energy generated by the electrosurgical device separately to a plurality of test loads, sensing a voltage and a current of the electrosurgical energy at an output of the electrosurgical device to obtain a plurality of sensed voltages and a plurality of sensed currents; calculating a sensor impedance value for each of the plurality of test loads based on the plurality of sensed voltages and the plurality of sensed currents; determining a phase value for each of the plurality of test loads based on a polynomial function of the sensor impedance value to obtain a predicted phase value; calculating an impedance loss model parameter associated with the transmission line based on the predicted phase value for each of the plurality of test loads and a previous impedance loss model parameter; and calculating a voltage and a current at a test load based on the plurality of sensed voltages, the plurality of sensed currents, and the impedance loss model parameter.