Asymmetric TTFields Electrode Layout to Reduce Electrosensation
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Solution Overview
Problem
Alternating electric fields used in treatments like TTFields can cause electrosensation, such as vibratory sensations or muscle contractions, discouraging subjects from continuing their treatment due to interactions with nerve cells near the transducer arrays.
Innovation Solution
The method involves using larger cathodes and smaller anodes with specific polarity and area relationships to reduce current density at the cathode, applying electrical pulses and signals in alternating sequences to balance charge and minimize electrosensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alternating electric fields are applied at higher amplitudes to improve therapeutic efficacy, then treatment effectiveness is improved, but electrosensation increases causing subject discomfort
Solution Approach 1:
The patent applies asymmetric electrode configuration where the cathode has a larger surface area than the anode. This asymmetry creates unequal current density distribution, with lower current density at the cathode (which causes electrosensation) and higher current density at the anode (which is less sensitive). This resolves the contradiction by allowing higher overall amplitudes for therapeutic efficacy while reducing electrosensation through the asymmetric area ratio.
Solution Approach 2:
The patent modifies the local quality of the electrode-tissue interface by creating different current density conditions at different locations. The larger cathode area specifically targets the region where electrosensation occurs, providing localized current density reduction at the cathode while maintaining or enhancing current density at the anode for therapeutic effect.
2Object-affected harmful factors
If larger cathodes are used to reduce current density and electrosensation, then electrosensation is reduced, but charge balance becomes more difficult to maintain
Solution Approach 1:
The patent changes the geometric parameter of the electrodes (area ratio) to simplify the charge balancing problem. By setting the cathode area to be at least twice the anode area, the system naturally accommodates the charge balancing requirement. The signal generator then applies charge-balanced signals where the integral of amplitude over time from the anode equals the integral from the cathode, making charge balance more achievable despite the area difference.
3Reliability
If alternating electric fields are applied to treat tumors, then therapeutic effect is achieved, but electrosensation occurs causing muscle contractions and discomfort
Solution Approach 1:
The asymmetric electrode design with larger cathode area reduces current density at the cathode, which is the primary source of electrosensation and muscle contractions. This allows the alternating electric field treatment to proceed with reduced discomfort, improving subject compliance and ease of operation while maintaining tumor treatment efficacy through the anode's higher current density.
Solution Approach 2:
The patent converts the harmful effect of high current density at the cathode (which causes electrosensation) into a beneficial configuration. By making the cathode larger, the system transforms what would be a high-current-density problem into a low-current-density solution, reducing electrosensation while maintaining therapeutic effectiveness through the complementary anode configuration.
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 effectively reduces or eliminates electrosensation during treatments, allowing subjects to continue therapy without discomfort, while maintaining the therapeutic efficacy of the electric fields.
Implementation Method 1
alternating electric fields e.g., at 50-500 kHz can increase the permeability of cell membranes so that large molecules can traverse cell membranes
Implementation Method 2
alternating electric fields e.g., at 50-200 kHz can increase the permeability of the blood brain barrier (BBB) so that, e.g., chemotherapy drugs can reach the brain
Implementation Method 3
Tumor Treating Fields, or TTFields, are alternating electric fields within the intermediate frequency range (e.g., 100-500 kHz) that inhibit cancer cell growth
Data Source
AI summary
When treating a subject using alternating electric fields (e.g., using TTFields to treat a tumor), some subjects experience an electrosensation effect. This electrosensation can be reduced or eliminated by applying a plurality of electrical pulses between two sets of electrode elements positioned on opposite sides of the target region. During the pulses, one set of electrode elements operate as the anode and the other set of electrode elements operate as the cathode. Electrosensation is reduced or eliminated because the collective area of the cathode is at least twice as large as the anode. An electrical signal with the opposite polarity is also applied to charge-balance the plurality of electrical pulses. The plurality of electrical pulses has an average amplitude that is at least twice the average amplitude of the charge-balancing signal.