Dosimetry and Temperature Evaluations of a 1800 MHz
TEM Cell for in Vitro Exposure with Standing Waves
A 1800 MHz transverse electromagnetic wave (TEM) cell is introduced for experiments investigating effects on biological samples caused by the exposure from mobile communications. To characterize and quantify the exposure environment in the setup for standardized in vitro experiments, we evaluate the dosimetry and the exposure-induced temperature rise in cultured cells. The study is numerically based on the finite-difference time-domain (FDTD) formulation of the Maxwell equations and the finite-difference formulation of the bioheat transfer equation, with all algorithms and models strictly validated for accuracy. Two sample formations of cells are considered including the cell layer and the cell suspension cultured in the 35 mm Petri dish. The TEM cell is designed to establish standing waves with the maximum E field and the maximum H field, respectively, at the position of the Petri dish. The Petri dish is oriented to E, -E, H, k, and -k directions of the incident field, respectively, to receive the exposure. The specific absorption rate (SAR) is calculated in cells for 10 exposure arrangements combined from the maximum fields and Petri dish orientations. A comparison determines the best arrangement with the highest exposure efficiency and the lowest exposure heterogeneity. The dosimetry and the exposure-induced temperature rise in cells are evaluated for the selected arrangement. To avoid thermal reactions caused by overheating, the maximum temperature rises in cells are recorded during the exposure. Based on the records, the temperature control is performed by setting limits to the exposure duration. We introduce a method to further reduce the exposure heterogeneity and evaluate the influence of the Petri dish holder on the dosimetry and temperature rise. The study compares the TEM cell to the waveguide, as well as the standing wave exposure to the propagating wave exposure. The TEM cell and the selected arrangement of the standing wave exposure improve the exposure quality over the traditional methods, with increased efficiency and decreased heterogeneity of the exposure.