Numerical and experimental dosimetry of petri dish exposure setups

Abstract

Crawford TEM cells are often used to expose cell cultures or small animals in order to study the effects caused by high-frequency fields. They are self-contained, easy-to-use setups that provide a rather homogeneous field distribution in a large area around its center, corresponding approximately to far-field conditions. However, a number of conditions must be met if such TEM cells are intended to be used for in vitro experiments. For instance, poor interaction with the incident field must be maintained to avoid significant field disturbances in the TEM cell. This is best achieved with E-polarization, i.e., when the E-field vector is normal to the investigated cell layer lining the bottom of a synthetic Petri dish. In addition, E-polarization provides the most homogeneous field distribution of all polarizations within the entire layer of cells. In this paper, we present a detailed dosimetric assessment for 60 and 100 mm Petri dishes as well as for a 48-well titer plate at 835 MHz. The dosimetry was performed by using numerical computations. The modeling and the simplifications are validated by a second numerical technique and by experimental measurements. For thin liquid layers, an approximation formula is provided with which the induced field strength for many other experiments conducted in Petri dishes can be assessed reliably.

Evaluation of hematopoietic system effects after in vitro radiofrequency radiation exposure in rats

“…The expected SAR profile was guided by the analysis presented in (Burkhardt et al 1996). In an idealised set-up (where the geometry can be simplified to that of a thin horizontal conductive sheet subject to an E-field that is vertically polarised), the authors derive analytical formulae that suggest the SAR is highest at the bottom and top of the Petri dish, and uniform in the horizontal direction.…”

“…Figure 1 highlights the uniformity of SAR in the bottom layer where the bones lie. This is in line with the theoretical approach of (Burkhardt et al 1996), where, the SAR profile is uniform in the horizontal direction (apart from near the sides of the dish), and highest at the top and the bottom. Due to the uniformity of SAR distribution along the bottom of the dish, the precise positioning of the bones on the bottom layer was not critical.…”

“…TEM cell can generate a well defined and homogeneous RF field distribution in the central area between the septum and the top (or bottom) walls (Burkhardt et al 1996). Factors that must be considered when conducting an RF dosimetric assessment of an in vitro sample include the dielectric properties, geometry, size, and orientation of the sample as well as the field polarisation, frequency and modulation characteristics of the RF exposure (Chou et al 1996).…”

Tumor specific gene expression profiles in human leiomyosarcoma

“…The cells, which intially float in the medium, line down on the bottom of the petri disk in a few minutes. For this reason the attenuation of field at the bottom of the petri dish used can be ignored since it has been calculated to be less than 2% (Burkhardt et al, 1996). The medium was always pre‐heated at 37°C in order to avoid the temperature raise time and the stress to the cells.…”

The radial transmission line as a broad-band shielded exposure system for microwave irradiation of large numbers of culture flasks

“…4A. Medium volume is an important parameter because eddy currents (and hence SAR) are expected to increase quadratically with medium height [Burkhardt et al, 1996;Staff, 1943], while thermal diffusion affects the plateau linearly with increasing thickness. Numerical simulations revealed that thermal diffusion effects should have become steady with medium volumes of Շ40 ml.…”