Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/3085

Title

A new coaxial line in vitro exposure device for fluorescent microscopy imaging during concurrent 900 MHz RF exposure

Author(s)

Anderson, Vitas;  Wood, Andrew W.

Abstract

OBJECTIVE: To develop a radiofrequency (RF) exposure device that allows accurate quantifiable RF field exposures of biological cells while being imaged by a confocal or general fluorescence microscope. RESULTS: The device consists of a cylindrical cell medium chamber at the end of a modified coaxial transmission line (Figure 1). It provides a perfusable, temperature controlled environment for maintaining cells in physiological or viable conditions and is easily disassembled for cleaning and autoclaving. Temperature is continuously monitored inside the device with a fluoroptic temperature probe, and stable temperatures (37 0.2°C) have been obtained for 2 W/kg exposures. The device is small enough to fit on any inverted microscope stage and can be used with standard microscope objectives. A glass coverslip forms the floor of the cell chamber and tissue slices or cells resting on the coverslip are viewed through a central 1 mm diameter hole in an underlying steel shim. The purpose of the shim is to shield the cells from the electromagnetic scattering influence of the nearby objective. Near the center of the hole, the optical imaging quality of cells in the device is not degraded relative to normal coverslip viewing conditions for cells. RF exposures inside the device were analysed using Method of Multipoles (MMP) electromagnetic modeling software (Hafner C. and Bomholt L. The 3D Electromagnetic Wave Simulator, Wiley, 1993) and found to be in excellent agreement with return loss and SAR measurements. The device provides a uniform SAR distribution throughout the volume of the cell chamber and generates high SARs for small forward power inputs. For a 1 W input the SAR distribution inside the cell chamber has a mean of 182.5 W/kg and a standard deviation of 15.7 W/kg. However, there is a substantial local perturbation of the field in the area immediately above the viewing hole. This perturbation has been quantified and was found to be partially influenced by the characteristics of the microscope objective (Figure 2) such as working distance and the presence of immersion media (oil or water). The total error in SAR exposure of the imaged cells due to uncertainty in the accuracy of the field calculations, the level of power delivered to the device, and locational error is estimated to be 0.8 dB. DISCUSSION: All aspects of the exposure field (SAR, |E|, |H|, polarization, phase, impedance) have been documented to provide a comprehensive picture of the field exposure. This information is particularly useful for testing hypotheses of athermal mechanisms, where SAR may not be the only relevant metric of exposure. The high uniformity of exposure allows investigation of power density window effects, and the unusual feature of enabling observation of cells during exposure is particularly useful when studying endpoints (such as [Ca++]i ) which are subject to strong homeostatic mechanisms. Finally the high efficiency of the device allows relatively high exposures without the need for expensive RF amplification equipment.

Publication type

Conference abstract

Research centre

Swinburne University of Technology. Faculty of Life and Social Sciences

Source

Proceedings of the 22nd Annual meeting of the Bioelectromagnetics Society, St. Paul, Minneapolis, USA, 10-14 June 2001

Publication year

2001

Publisher URL

http://www.bioelectromagnetics.org/pubs.php#abstracts