P. Gas, and A. Miaskowski, “Specifying the ferrofluid parameters important from the viewpoint of Magnetic Fluid Hyperthermia”, 2015 Selected Problems of Electrical Engineering and Electronics (WZEE), IEEE Xplore, 2015, art. no. 7394040, [pp. 1-6]. Available at: http://dx.doi.org/10.1109/WZEE.2015.7394040 978-1-4673-9452-9/15/$31.00 ©2015 IEEE Specifying the ferrofluid parameters important from the viewpoint of Magnetic Fluid Hyperthermia Piotr Gas AGH University of Science and Technology Department of Electrical and Power Engineering al. Mickiewicza 30, 30-059 Krakow, Poland e-mail: piotr.gas@agh.edu.pl Arkadiusz Miaskowski University of Life Sciences in Lublin, Department of Applied Mathematics and Computer Sciences Akademicka 13, 20-950 Lublin, Poland e-mail: arek.miaskowski@up.lublin.pl Abstract — The article presents the experimental study of magnetic fluid hyperthermia (MFH) utilizing magnetite nano- particles with diameter of 15.2 nm. Temperature measurements of the ferrofluid samples were carried out in real measurement system using parallel resonance phenomenon. Based on the obtained temperature curves the basic heating parameters of ferrofluid, namely the Specific Absorption Rate (SAR) and power losses in tested nanoparticles have been specified. The authors systematize the current knowledge of these quantities and addi- tionally propose two models that simplify their determination with given errors, omitting the mass and volume concentrations of the individual components of magnetic fluid. Keywords — magnetic fluid hyperthermia; specific absorption rate; power losses; superparamagnetic nanoparticles; resonance; temperature measurements I. INTRODUCTION The ability of magnetic nanoparticles (MNPs) to function as an efficient source of heat has been shown many years ago [1]. However, in the last few years MNPs gained interest due to their easy injection into the body and use for medical purposes. Using localized magnetic field gradients it is possible to deliver such particles to a target tissue, and thus impact on local hyperthermia (HT), chemo-, radiotherapy, immunotherapy, or gene therapy in the tumor [2]. In some cases, the magnetic fluid (MF) can be injected directly into the tumor and heated using magnetic fields produced by external applicators [3]. In the majority of hyperthermia techniques many problems in heating of the deep seated tumors are observed. Difficulties are mainly manifested by surface tissue burning in direct contact with the applicator and the overheating of healthy tissues surrounding the tumor [4]. Nowadays, the researchers repose high hopes in usage of nanotechnology in cancer treatment, drug delivery, molecular diagnostics and imaging [5], [6]. MNPs of various types, sizes and magnetic properties are commonly tested during various in vivo and in vitro studies [7]. In the most cases the iron oxide nanoparticles (IONPs) like magnetite and maghemite as well as the iron-platinum and iron-cobalt magnetic nanoparticles are suited for magnetic fluid hyperthermia (MFH) [8], [36]. However, the most popular of them seems to be the colloidal magnetite NPs (Fe 3 O 4 ) because of assuring the best heating properties, low toxicity, good biological compatibility and tolerability by the human body [9]. The ferrofluids, based on Fe 3 O 4 , have also some important technical applications [10]. Utilizing of MNPs in thermal therapy allowed focusing electromagnetic (EM) energy strictly into targeted tissue, thereby minimizing the negative side effects of conventional HT methods [11]. The phenomenon of conversion of the power loss into the heat in MNPs is essential for the treatment of tumors during the MFH procedures. These losses are connected with changes in magnetization of MNPs exposed to external alternating (AC) electromagnetic field (EMF) and are caused mainly due to hysteresis loss as well as Neel and Brown relaxation losses [12], [13]. It should be emphasized that the heating capacity of the ferrofluid significantly depends on the size and shape of nanoparticles as well as on the material properties. Moreover, the diameter of the colloidal MNPs may be successfully measured using various techniques including the dynamic light scattering (DLS) [14]. The paper presents results of in vitro calorimetric tests of magnetic fluid HyperMAG ® C that was heated up in the real measuring system magneTherm TM . In the current literature on experimental investigations of various ferrofluids there is enormous confusion in identification of the basic parameters necessary to evaluate the thermal exposures of the MNPs. The scientists often give contradictory definitions in this matter within their papers. For this reason, the authors attempt to systematize the fundamental concepts associated with MFs, what is fully justified. Based on the ferrofluid temperature characteristics, the main parameters as the Specific Absorption Rate (SAR) and power dissipated in the test MNPs have been specified. In addition, the authors propose two simplified models to determine the heating parameters of used magnetic fluid, omitting the mass and volume concentrations of the individual components of magnetite suspension. Moreover, the detailed description of the performed experiment helps in understanding the theory governed the MFH occurring in the external AC electromagnetic field. II. BASIC DEFINITIONS One of widely discussed aspects of the interaction EMFs on biological structures is an attempt to normalize energy processes occurring in living tissues under the influence of applied EMF. For this purpose, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) introduced the so-called Specific Absorption Rate (SAR) to determine the amount of EM energy induced in mass unit of the exposed object according to the relation [15], [16]: