Background: Currently, various types of heat treatment modalities are available, but none of these methods have the ability to accurately deliver high heat energy to deeply seated tumors without damaging the healthy surrounding tissues. In this work, by the effective usage of DC Magnetic Field Gradients and Magnetic Fluids, a novel RF ablation system was developed which is capable of focusing the heat into very small regions in the order of millimeters.

Methods: By depositing appropriate DC magnetic field gradients on the AC magnetic fields one can generate AC field dominant regions and achieve focused heating of the magnetic particles at these regions. Figure1a shows a focused ablation system that accomplishes this task. Here, two solenoids on the right and left are fed with equal but opposite DC currents. The solenoid in the middle is fed with an AC current.
Various experiments were made on the focused ablation system. Three different DC magnetic field conditions were tested by applying different static currents to DC solenoids. In, in vitro experiments(Figure1a), three plastic cups, filled with ferrofluid were placed in the middle.
In vivo experiments were done on the tails of adult rats and ferrofluids were injected percutaneously to the tails.

Results: The temperature rise of the central cup doesn’t change(Figure2) while the temperature rise of the lateral cups decreases as the amplitudes of the DC currents increases. This shows that focusing is achieved succesfully by increasing the DC current amplitudes. Also, results showed that position of the focus can be easily shifted(Figure2, rightmost plot).
Results of the rat experiments successfully verified the focusing ability of the system, where detailed macroscopic and histological examinations of the rat tails were done.

Conclusions: A novel focused ablation system, capable of heating deeply seated tumors without damaging any surrounding tissue is implemented and verified through experiments.