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Figure 8.21 The maximum temperature inside the heated tissue as a function of the antenna
power for constant versus temperature-dependent dielectric tissue properties. Adapted from
Morega, M., Neagu, M., Morega, A.M., 2008. Bidirectional coupling of electromagnetic and thermal pro-
cesses in radiofrequency hyperthermia. In: Proceedings of the 12th International Conference on
Optimization of Electrical and Electronic Equipment—OPTIM 2008, Brasov, Romania, pp. 257 262.

smaller dose of radiation with magnetic hyperthermia (then radiation alone) (Johannsen
et al., 2010). Several magnetic nanomaterials were considered for their potential for hyper-
thermia, including Iron oxide nanoparticles (Fe 3 O 4 and γ Fe 2 O 3 ) stabilized by ligands
such as dextran, PEG, and polyvinyl alcohol, to increase their circulation time in the body
and to prevent clearance by the Mononuclear phagocyte system (MPS) (Itoetal.,2005;Kumar
and Faruq, 2011). The Iron oxide MNPs are nontoxic, highly biocompatible, and they are
metabolized to form blood hemoglobin, thus maintaining homeostasis of iron inside cells.
Other promising applications of MNPs are in the controlled drug release for the treatment
of diseases including tumors. MNPs along with therapeutic molecules are encapsulated in a
pH or heat-sensitive polymers. Drug release can be triggered by external stimuli. For sensi-
tive polymers, the heat generated within the MNPs may lead to the formation of pores in
polymers, resulting in releasing therapeutic molecules.
Magnetic hyperthermia uses MNPs delivered at the tumor site before the application of
the EMF. MNPs can be passive, by convection diffusion mechanisms invascularizedtis-
sues, or active, using targeting surface-attached ligands for binding to appropriate receptors
expressed at the tumor site and not expressed by normal cells (Danhier et al., 2010).

The magnetic field work interactions
The external magnetic field work interaction with the MNPs depends on the frequency and
on the size and other characteristics of the MNPs, and, in ferrofluids, it occurs through
two mechanisms: hysteresis (Warburg theorem, Chapter 1: Physical, Mathematical, and
Numerical Modeling), because small particles exhibit a large hysteresis loop, and