Browsing by Subject "Hyperthermia"

Now showing 1 - 2 of 2

Open Access
Focused RF ablation using magnetic fluids
(2006) Taşçı, T. Onur
In most developed countries, cancer is presently responsible for about 25% of all deaths. Heat therapies like hyperthermia and thermoablation are very promising approaches in the treatment of the cancer. Since these are physical treatment methods they have fewer side affects compared to chemo- and radio-therapy. Currently, various types of heat treatment modalities are available like microwave, ultrasound, RF capacitance hyperthermia, RF probe hyperthermia, magnetic fluid hyperthermia, but non of these methods have the ability to accurately deliver high heat energy to deeply seated tumors without damaging the healthy surrounding tissues. In this thesis, a novel RF ablation system was developed capable of focusing the heat in to very small areas in the order of millimeters, which will allow heating of the tumors without destroying collateral normal tissues. Generally, in this system the tumor ablation is achieved via coupling RF energy on the magnetic fluids which are previously dispersed in to the tumor tissue. By considering the human safety limits (nerve stimulation and tissue eddy current heating safeties) optimum treatment parameters like particle size of the magnetic fluids, frequency and strength of the applied RF field are obtained. The utilization of the optimum parameters may lead to the very effective operation of the ablation system where treatments can be done with very small amounts of fluid injections, in short durations. We believe that by the studies conducted in this thesis, magnetic fluid hyperthermia (tumor ablations using magnetic fluids) can be a much more effective method so that it can be used as the one of the most important tumor treatment techniques in future.
Open Access
Focused RF hyperthermia using magnetic fluids
(WILEY, 2009-04-27) Tasci, T. O.; Vargel, I.; Arat, A.; Guzel, E.; Korkusuz, P.; Atalar, Ergin
Heat therapies such as hyperthermia and thermoablation are very promising approaches in the treatment of cancer. Compared with available hyperthermia modalities, magnetic fluid hyperthermia (MFH) yields better results in uniform heating of the deeply situated tumors. In this approach, fluid consisting of superparamagnetic particles (magnetic fluid) is delivered to the tumor. An alternating (ac) magnetic field is then used to heat the particles and the corresponding tumor, thereby ablating it. However, one of the most serious shortcomings of this technique is the unwanted heating of the healthy tissues. This results from the magnetic fluid diffusion from the tumor to the surrounding tissues or from incorrect localization of the fluids in the target tumor area. In this study, the authors demonstrated that by depositing appropriate static (dc) magnetic field gradients on the alternating (ac) magnetic fields, focused heating of the magnetic particles can be achieved. A focused hyperthermia system was implemented by using two types of coils: dc and ac coils. The ac coil generated the alternating magnetic field responsible for the heating of the magnetic particles; the dc coil was used to superimpose a static magnetic field gradient on the alternating magnetic field. In this way, focused heating of the particles was obtained in the regions where the static field was dominated by the alternating magnetic field. In vitro experiments showed that as the magnitude of the dc solenoid currents was increased from 0 to 1.8 A, the specific absorption rate (SAR) of the superparamagnetic particles 2 cm apart from the ac solenoid center decreased by a factor of 4.5, while the SAR of the particles at the center was unchanged. This demonstrates that the hyperthermia system is capable of precisely focusing the heat at the center. Additionally, with this approach, shifting of the heat focus can be achieved by applying different amounts of currents to individual dc solenoids. In vivo experiments were performed with adult rats, where magnetic fluids were injected percutaneously into the tails (with homogeneous fluid distribution inside the tails). Histological examination showed that, as we increased the dc solenoid current from 0.5 to 1.8 A, the total burned volume decreased from 1.6 to 0.2 cm3 verifying the focusing capability of the system. The authors believe that the studies conducted in this work show that MFH can be a much more effective method with better heat localization and focusing abilities.