Electromagnetic Thermotherapy for Deep Organ Ablation by Using a Needle Array Under a Synchronized-Coil System

Thermal ablation by using electromagnetic thermotherapy (EMT) has been a promising cancer modality in recent years. It has relatively few side effects and has therefore been extensively investigated for a variety of medical applications in internal medicine and surgery. The EMT system applies a high-frequency alternating electromagnetic field to heat up the needles which are inserted into the target tumor to cause tumor ablation. In this study, a new synchronized-coil EMT system was demonstrated, which was equipped with two synchronized coils and magnetic field generators to provide a long-range, penetrated electromagnetic field to effectively heat up the needles. The heating effect of the needles at the center of the two coils was first explored. The newly designed two-section needle array combined with the synchronized-coil EMT system was thus demonstrated in the in vitro and in vivo animal experiments. Experimental data showed that the developed system is promising for minimally invasive surgery since it might provide superior performance for thermotherapy in cancer treatment.

I. Introduction

Thermal ablation [1], [2] has been a popular method for cancer treatment or other treatments since its advent. This method involves rapid and local heating of the tumor or tissue to above 60 °C to cause necrosis of tumor cells. It is a simple therapy with relative few side effects and fewer complications. Recently, thermal ablation has been combined with minimally invasive surgery (MIS) [3], [4] as a new approach for treating cancer or other organ-enlargement diseases. For example, radio frequency ablation (RFA) [5]–[7] and microwave ablation [8]–[10] have all been applied in a variety of cancer treatments such as organ resection surgery and necrosis of tumor cells in internal medicine. Briefly, RFA employs a probe and a power generator to provide the required heating when an alternating electric current passes through the probe with a frequency ranging from 460 to 500 kHz. The temperature of the tissue could be rapidly and efficiently raised to about 100 °C locally such that the tissue ablation occurs. Alternatively, microwave ablation is another treatment approach using thermal ablation in which a probe delivers microwave energy to heat up water molecules in the cells and therefore generate a high temperature to cause ablation in the tissue. Applying RFA or microwave ablation in needle-array layout or large-range tumor treatment, however, is challenging because RFA and microwave ablation probes are expensive. The number of probes that could be simultaneously applied during treatments is thus limited to two to four probes [11], [12], which may hinder their practical applications in large-range treatment or organ-enlargement treatment.