Investigating Gelatine Based Head Phantoms for Electroencephalography Compared to Electrical and Ex Vivo Porcine Skin Models

Abstract

Gelatine based phantoms for electrophysiology are becoming widely used as they allow the controlled validation of new electrode and new instrumentation designs. The phantoms mimic the electrical properties of the human body and allow a pre-recorded electrophysiology signal to be played-out, giving a known signal for the novel electrode or instrumentation to collect. Such controlled testing is not possible with on-person experiments where the signal to be recorded is intrinsically unknown. However, despite the rising interest in gelatine based phantoms there is relatively little public information about their electrical properties and accuracy, how these vary with phantom formulation, and across both time and frequency. This paper investigates ten different phantom configurations, characterising the impedance of the gelatine and electrodes, comparing this to both previously reported electrical models of Ag/AgCl electrodes placed on skin and to a model made from ex vivo porcine skin. This article shows how the electrical properties of the phantoms can be tuned using different concentrations of gelatine and of sodium chloride (NaCl) added to the mixture, and how these properties vary over the course of seven days for a.c. frequencies in the range 20-1000 Hz. The results demonstrate that gelatine phantoms can accurately mimic the frequency response properties of the body-electrode system to allow for the controlled testing of new electrode and instrumentation designs.INDEX TERMS Gelatine phantoms, tissue-mimicking, electrical properties, electrophysiology, electroencephalography (EEG), electrocardiogram (ECG).

Fully printed and multifunctional graphene-based wearable e-textiles for personalized healthcare applications

“…The PSG data is scored into different sleep stages by a trained expert to identify sleep disorders (Sharma et al, 2021;Yildirim et al, 2019). To demonstrate the feasibility of using the e-textiles for EEG recordings, we simulate the EEG part of a PSG using two electrodes and a gelatine head phantom (Owda and Casson, 2021), Figure 5A. This setup simulates one EEG electrode placed on the central forehead (referred to to as Fpz in the international 10-20 standard), and a reference electrode placed elsewhere (here, we utilize the Cz location, which is in the center of the scalp).…”

Skin and Artificial Skin Models in Electrical Sensing Applications

“…A relatively thorough study was conducted by Owda and Casson in which they investigated the electrical properties of gelatin models and evaluated them as phantoms for electrophysiological measurements. 111 They made gelatin models with variations of gelatin content and salt concentration and conducted impedance measurements over the frequency range of 20−1000 Hz. Figure 15a,b shows the test setup in which the tests were performed on the skin model and on porcine skin, respectively.…”

“…(a) Test setup for impedance measurements on the gelatin-based skin model developed by Owda and Casson . One Ag/AgCl electrode is embedded within the gel, and the other is mounted on the top surface of the model.…”

“…(c) Example of the impedance results for a selected skin model in a 7 day period compared to those of the porcine skin. Reproduced with permission from ref with minor modifications. Copyright [2021] [IEEE].…”

3D-printed, directly conductive and flexible electrodes for personalized electroencephalography

“…To systematically characterize the electrical properties of the new electrodes, an EEG phantom was used for measurements of electrode contact impedance, contact noise, drift rate, and power line noise susceptibility. A cuboid phantom was used in this work, made of water and pork gelatine powder, as previously reported in [14,21,22]. Here we used 20% gelatine concentration per mass, with no added NaCl.…”