| Abstrakt: |
The motivation for this work arose from the desire to measure the temperature distribution in phantom material and in mouse tumours when irradiated with microwaves launched from a miniature coaxial line applicator embedded in the medium. The design and construction of this applicator has been described in a previous publication (Szwarnowski et al., 1980). The small size of the tumours and the compact field produced by the applicator required the use of very small temperature-measuring probes. The only type of thermometric probe of sufficiently small dimensions which was readily available and convenient to use was a thermocouple.However, it has long been recognized that a thermocouple is not suitable for measuring temperature in an electromagnetic field, due to the interaction of the field with the metals of the thermocouple and its connecting leads (Johnson and Guy, 1972; McRee and Pendergrass, 1973). It has been suggested (Allis et al., 1975; 1977) that thermocouples with shielded leads perpendicular to the field may be used. However, this would not be practicable, for example, in a tumour where the direction of polarization of the wave could not be determined.Alternative methods of temperature measurement exist, such as high resistivity thermistors with highresistance connecting leads (Bowman 1975; 1976); but these are difficult to construct and are not readily available. Liquid-crystal thermometers (Olsen et al., 1973; Johnson et al., 1974; Rozzell et al., 1974; Deficis and Priou, 1977) do not interact with the electromagnetic field. |
