Pink (1/f) noise is one of the most common behaviours of biosystems. Our present paper is devoted to clarify the origin of this interesting phenomenon. It is shown that the stationary random stochastic processes under self-similar conditions (as we have in living objects) generate pink noise independently of the kind and number of variables.

The classical hyperthermia effect is based on well-focused energy absorption targeting the malignant tissue. The treatment temperature has been considered as the main technical parameter. There are discussions about the mechanism and control of the process because of some doubts about the micro-mechanisms. The main idea of the extracellular hyperthermia is to heat up the targeted tissue by means of electric field, keeping the energy absorption in the extracellular liquid. This produces a temperature gradient and connected heat flow through the cell membrane, which initializes numerous nonequilibrium thermal microprocesses to destroy the cell membrane. Furthermore, before the heat shock activates the intracellular heat shock protein (HSP) mechanisms, the cell membrane has been already compromised, therefore the HSP synthesis in the cells starts secondarily only after the membrane damage. The process could explain why the nonuniform and basically unsatisfactorily high temperature locoregional hyperthermia could be effective.

Comparison of thermal noise limits and the effects of low frequency electromagnetic fields (LFEMF) on the cellular membrane have important implications for the study of bioelectro-magnetism in this regime. Over a decade ago, Weaver and Astumian developed a model to show that thermal noise can limit the efficacy of LFEMF. A recent report by Kaune [Kaune (2002) Bioelectromagnetics 23:622-628], however, contradicted their findings. Kaune assumes that the conductance noise current of cell membrane can be decomposed into two components, where one of them is identical regarding all segments (coherent), while the other is different (incoherent). Besides, this decomposition is not unequivocal and contradicts to the statistical independence of the segment noise currents, and therefore to the second law of thermodynamics as well. We suggest the procedure based on the method of symmetrical components, by the means of which we can re-interpret the result of Kaune in a correct way.

We shall assume, of course, that the objective of hyperthermia is to destroy the malignant cells. Destruction definitely needs energy. Description and quality assurance of hyperthermia use the Pennes heat equation to describe the processes. However the energy balance of the Pennes-equation does not contain the hyperthermic cell-destruction energy, which is a mandatory factor of the process. We propose a generalization of the Pennes-equation, inducing the entire energy balance. The new paradigm could be a theoretical basis of the till now empirical dose-construction for oncological hyperthermia. The cell destruction is a non-equilibrium thermodynamical process, described by the equations of chemical reactions. The dynamic behavior (time dependence) has to be considered in this approach. We are going to define also a dose concept that can be objectively compared with other oncological methods. We show how such empirical dose as CEM43oC could be based theoretically as well.

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