Design, implementation, and dosimetry analysis of an S‐band waveguide in vitro system for the exposure of cell culture samples to pulsed fields

Abstract

The interaction between electromagnetic fields and biological media, particularly regarding very high power, short pulses as in radar signals, is not a fully understood phenomenon. In the past few years, many in vitro, cellular communications-oriented exposure studies have been carried out. This article presents a high-power waveguide exposure system capable of dealing with monochromatic, multicarrier or pulsed signals between 1.8 and 3.2 GHz (L- and S-band) with a pulse duration as low as 90 ns, minimum pulse repetition of 100 Hz, and maximum instantaneous power of 100 W. The setup is currently being used with a 2.2 GHz carrier modulated by 5 micros pulses with a 100 Hz repetition period and approximately 30 W of instantaneous power. After a worst-case temperature analysis, which does not account for conduction and convection thermal effects, the experiment's exposure is considered sub-thermal. Evaluation of the results through the specific absorption rate distribution is not considered sufficient enough in these cases. An electromagnetic field distribution analysis is needed. For monochromatic signals, the representation of the modulus of the electric and magnetic field components is proposed as a suitable method of assessment.

Cytostatic response of NB69 cells to weak pulse-modulated 2.2 GHz radar-like signals

“…The system for in vitro-exposure is illustrated in Figure 1 and is identical to that described in a previous paper by Varela et al [2010], except for the signal generator and modulator specifically used in the present study. The system was designed for evaluation of the cellular response to pulse-modulated, radar-like signals, which are characterized by high RF instantaneous amplitudes with very low average power.…”

“…Since RF exposure at work has been proposed as a potential factor in human cancer promotion, we have investigated the responses of two human cancer cell lines, NB69 from a neuroblastoma and HepG2 from a hepatocarcinoma, to an RF radarlike signal. The study was conducted using a newly designed double waveguide applicator for in vitro exposure to RF signals inside commercial CO 2 incubators [Varela et al, 2010]. Taking into account the mean specific absorption rate (SAR) value (0.023 W/ kg) in space and time and the heat diffusion effect, the temperature rise in the cultures due to the 24-h exposure to the chosen RF parameters would be negligible.…”

High-accuracy adaptive modeling of the energy distribution of a meniscus-shaped cell culture in a Petri dish

“…Some authors state that in addition to control the SAR, one also needs to impose some additional conditions, e.g., polarization, on the distribution of the full electromagnetic fields to secure the proper evolution of the cell culture (see [22] and references therein). Furthermore, the meniscus shape developed at the interface of the liquid with the dish provides a complex shape, whose geometry is typically expressed as a mathematical formula involving exponential and hyperbolic functions.…”

“…Moreover, it should provide an error estimation in order to minimize uncertainty and guarantee the correctness of the solution for each model. Several numerical methods have been employed for Petri dish simulations exposed to EM fields in different configurations, e.g., [3,20,21,16,1,22,23]. Approaches based on differential formulations are mainly used because of their flexibility to deal with complex geometrical and material configurations.…”

“…Unfortunately, the use of small voxel sides ofthe order of one tenth (or even one hundredth) of a wavelength may not be enough in some cases to have confidence on the results. In those situations, the voxels close to the solid/liquid interface are skipped from the SAR distribution assessments, as it is reported in [22].…”