A shape memory alloy probe for electrovaporization of renal cell carcinoma.

Abstract

e15090 Background: We developed a new shape memory alloy (SMA) probe for percutaneous treatment of renal cell carcinoma (RCC) by electro-vaporization, and investigated its efficacy and safety in experimental models. Methods:The SMA electrode can be manipulated to any shape at room temperature and regains its original shape at ≥ 65 °C. By adding a high-frequency electric current to the probe, the electrodes quickly regain their original shape and vaporize tissues into a spherical defect. The performance of this probe was tested using agar, dog kidney and rat RCC models. The treatment effect was evaluated by magnetic resonance imaging (MRI) and histological examination. Results: The vaporizing electrode produces heat due to its own resistance to the high frequency electric current, and vaporizes surrounding agar. In the agar model, the electro-vaporization inside the spherical electrode was successfully achieved in several seconds. The area of ≥ 60 °C extended about 5 mm beyond the periphery of the vaporized part, and corresponded with the histological findings on the dog kidney that an irreversible heat denaturation occurred to the same extent. A tumor model made by transplanting RCC cell line in the subcutaneous tissue of nude rats. After applying the electorical current, the electrode part completely recovered to a full sphere shape. The study on the RCC model also confirmed that about 5 mm extent of heat denaturation was seen in the muscular tissue adjacent to the tumor. In the study using the RCC model, some remaining tissues close to the tumor were observed after vaporization. However, dynamic MRI demonstrated no enhancement in this area and no viable tumor cells were documented by histological examination. Conclusions: This novel tissue ablation system has potential as a viable option for percutaneous treatment of renal tumors.