A finite element model of the current distribution in the skin
Author
Pedersen, Mathilde
Term
4. term
Publication year
2009
Abstract
This thesis addresses how to target cutaneous nociceptors during transcutaneous electrical stimulation while avoiding activation of other sensory organs and nerve fibers. To investigate this, a finite element model of the skin’s electrical properties was developed to compute current density distributions under a concentric surface electrode. The skin was represented by two layers: the stratum corneum and a combined cellular epidermis/dermis, with skin appendages omitted. The diameter of the inner cathode was varied to test whether a smaller cathode would concentrate current density in the superficial layers where nociceptors are located. Simulations indicated that the current density in the upper layers, particularly at the edge of the cathode, was higher with a small cathode than with a large one. This suggests that smaller electrodes can stimulate nociceptors more selectively. The analysis uses current density as a proxy for potential activation and recommends incorporating explicit nerve fiber models in future work for direct activation estimates.
Dette speciale undersøger, hvordan elektrisk stimulation af huden kan målrettes mod nociceptorer uden samtidig at aktivere andre kutane sanseorganer og nervefibre. For at belyse dette blev der udviklet en finittelementmodel af hudens elektriske egenskaber, der beregnede strømtæthedsfordelingen ved brug af en koncentrisk overfladeelektrode. Modellens hudrepræsentation bestod af to lag: stratum corneum samt et samlet lag for den cellulære epidermis og dermis; hudappendager blev ikke inkluderet. Den indre katodes diameter blev varieret for at undersøge, om en mindre katode i højere grad kunne koncentrere strømtætheden i de øverste hudlag, hvor nociceptorerne befinder sig. Simulationerne viste, at strømtætheden i de øverste lag, især ved katodens kant, var større med en lille katode end med en stor katode. Dette peger på, at små elektroder mere selektivt kan stimulere nociceptorer. Arbejdet anvender strømtæthed som en indikator for mulig aktivering og anbefaler, at fremtidige modeller udvides med eksplicitte nervefibermodeller for at vurdere aktivering direkte.
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