In Vitro Dosimetry and Temperature Evaluations of a Typical Millimeter-Wave Aperture-Field Exposure Setup

Abstract

Aperture-field exposure setups are applied in experiments detecting the effects of millimeter-wave (MMW) exposure on cells in vitro. In this paper, the studied exposure setup with standard components includes cells plated in a 35-mm Petri dish at the aperture of a horn irradiating 50.0-GHz MMW. Incorporating the subvoxel model and symmetry formulas, the finite-difference time-domain algorithm of the Maxwell equations and the finite-difference algorithm of the Pennes bioheat equation are used to calculate the specific absorption rate (SAR), absorption efficiency of the MMW power, and temperature rise in the cell culture. The numerical methods and models are supported by experimental measurement and theoretical analyses. The exposure of 31.2-mW MMW results in an averaged SAR of 44.9 W/kg in cells, quantitatively compatible with the International Commission on Non-Ionizing Radiation Protection limits to the incident power density. 46.9% of the MMW power is efficiently absorbed and accumulates a maximum temperature rise of 0.12°C in cells. The exposure intensity is selectable with acceptable homogeneity by proper cell sampling. The MMW multiple reflection of the aperture-field exposure is analyzed about its significant influences on the dosimetry and temperature results. Another comparison reveals the efficacious power matching of the Petri dish and its dosimetric contribution. The power threshold for time-unlimited exposures, time limits for high-power exposures, and adaptive air cooling are quantified to control the temperature variance within ±0.1°C. This paper presents the first detailed quantification and characterization of the dosimetry and temperature environments for the MMW aperture-field exposure setup in application to in vitro experiments for over 30 years.