Distortion of millimeter-wave absorption in biological media due to presence of thermocouples and other objects

Specific absorption rate (SAR) distributions in the vicinity of a thermocou ple or air bubble in water and in the presence of hair or sweat duct in ski n were calculated using analytical and two-dimensional impedance methods. T he objects were exposed to uniform 42.25 GHz plane electromagnetic fields. Insertion of a 0.1-mm thermocouple or similarly sized air bubble into water produced a strong localized disturbance of the otherwise uniform SAR distr ibution. However, the average of SAR values immediately surrounding the the rmocouple was close to the undisturbed uniform average SAR. This allows mea suring the average SAR during exposure of both unbounded and bounded media using calibrated small thermocouples (up to 0.1 mm). The SAR distribution i n the vicinity of a hair was qualitatively similar to that produced by an a ir bubble. The maximal value of SAR was more than three times higher than t he overall average SAR value in the skin. Sweat ducts produced a smaller di sturbance of the millimeter-wave (mm-wave) field.