FDTD simulation of exposure of biological material to electromagnetic nanopulses

Abstract

Abstract.Ultra-wideband (UWB) electromagnetic pulses of nanosecond duration, or nanopulses, are of considerable interest to the communications industry and are being explored for various applications in biotechnology and medicine. The propagation of a nanopulse through biological matter has been computed in the time domain using the finite difference-time domain method (FDTD). The approach required existing Cole-Cole model-based descriptions of dielectric properties of biological matter to be re-parametrized using the Debye model, but without loss of accuracy. The approach has been applied to several tissue types. Results show that the electromagnetic field inside a biological tissue depends on incident pulse rise time and width. Rise time dominates pulse behavior inside a tissue as conductivity increases. It has also been found that the amount of energy deposited by 20 kV /m nanopulses is insufficient to change the temperature of the exposed material for the pulse repetition rates of 1 M Hz or less.

FDTD analysis of a gigahertz TEM cell for ultra-wideband pulse exposure studies of biological specimens

“…This clearly shows that only the short-time-scale features couple into the interior of the cell culture medium volume: as claimed in Section III-A, the slow-timescale tail feature of the measured waveform is ignorable. These results are completely consistent with the observations in [18] where only the fast-rise-time leading edge portion of their pulse penetrated the interior of the sample, while the slowly decaying trailing edge did not couple.…”

“…Under these exposure conditions, we conclude that a conservative upper bound for the maximum possible temperature rise due to the pulse train is on the order of . This verifies that the temperature rise is negligible during these UWB EMP exposure experiments, which is consistent with [18]. Consequently, any unusual cell function or histopathology can be associated with nonthermal effects.…”

“…In our study, we investigated the regime where the pulse width is comparable to the pulse rise time. This complements the results of [18] which focused on a specific regime in which the pulse width is much larger than rise time.…”

“…Such characterizations of field patterns in the unloaded GTEM cell cannot be used to reliably predict the spatial and temporal field variations inside cell-culture flasks inserted into the GTEM cell. The electromagnetic properties of a GTEM cell loaded with a cuvette has been investigated via numerical simulations [18]; however, that study was conducted in two-dimensional rather than three-dimensional (3-D). Experimental dosimetry techniques rely upon the use of in situ sensors, such as D-dot sensors [20], [21], placed inside the flasks.…”

Use of the z‐transform to investigate nanopulse penetration of biological matter

“…Moreover, it is not yet clear why bioeffects should depend on pulse width or rise time. Of course, the energy deposited in a sample will depend on pulse width, but when the pulse is so short, the temperature rise will be insignificant [Vernier et al, 2004;Simicevic and Haynie, 2005]. Further experimental study is needed to elucidate mechanisms of non-thermal effects.…”