Dielectric properties of biological tissue at low temperatures demonstrated on fatty tissue.

Dielectric behaviour of fatty tissue was investigated from T = 300 K to 4 K and f = 20 Hz to 1 MHz. Characteristic curves were obtained only at low frequencies. With decreasing temperature four important features were detected: the water-ice transition at T = 265 K, a relaxation process of the fat molecules (near 260 K) and one connected with the ice-part (210 K-170 K). The reason for the fourth relaxation at T = 140 K has not been fully understood yet: it may be caused by segmental rotation of the fatty acid molecules or the presence of multiple bonds. The epsilon"-maximum caused by the ice relaxation at T congruent to 200 K can be used to detect successful application of cryotherapy, i.e. the temperature fall below the minimum value of 233 K.

A measuring technique for the investigation of the dielectric behaviour of biological tissue at low temperatures.

The experimental technique described can be used to measure the complex dielectric constant of different kinds of samples in the temperature range T = 300 to 4K. The specially designed sample holder guarantees simple preparation and allows in-vitro measurements of biological tissues as well as investigations of related materials of interest including liquids. The results of fatty tissue chosen as a model substance will be shown and discussed in comparison to simple basic compounds in subsequent papers.