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Validity of Gabriel et al. tissue dielectric model below 10 Hz

Ascertain the validity of the Gabriel et al. parametric model for dielectric properties of biological tissues at frequencies below 10 Hz, which lie outside the experimental data range used for fitting, to ensure accurate selection of conductivity and permittivity for low-frequency neuromodulation waveforms.

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Background

The Gabriel et al. dielectric data and model are widely used to assign tissue electrical properties in neuromodulation simulations across 10 Hz to 20 GHz. The paper leverages these data to discuss the frequency dependence of tissue parameters relevant to QSA.

For very low frequencies (<10 Hz), the figure caption explicitly states that the model is extrapolated beyond its fitted range and its validity is unknown, which is critical for dc and near-dc stimulation regimes such as tDCS and certain pulsed protocols.

References

Dashed lines indicate extrapolation of the model to very low frequencies (<10 Hz), outside the range of experimental data (10 Hz to 20 GHz) to which the model was fitted, where the model has unknown validity.

— Quasistatic approximation in neuromodulation (2402.00486 - Wang et al., 1 Feb 2024) in Figure 2 caption, Section 2.4