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For a minimally invasive treatment of pathologic tissue, e.g. tumors, the benign prostate hyperplasia (BPH) or the concha hyperplasia in otorhinolaryngology (ENT), next to the laser- induced interstitial thermotherapy (LITT) or the monopolar HF- surgery the interstitial thermotherapy with high-frequency alternating current (HF-ITT) in bipolar technique is a good alternative. Investigation results are presented which prove the feasibility and show the performance of this technique. Bipolar needles of different geometries, adapted to the various application fields, such as palliative treatment of metastatic carcinomas in liver and concha hyperplasia, were built and tested. Basic investigations of the thermal field distribution in in vitro samples were performed. The efficiency of the developed applicators were examined in in vitro experiments with porcine liver, turkey breast and porcine concha. Coagulation volumes of different needle diameters and power settings are show. Carbonization and dehydration can be avoided by irrigation of the tissue during treatment through integrated flushing ports and thus the performance is increased. For the treatment of concha hyperplasia special designs are presented which could probably offer an additional increase of safety and a simplification of performing a concha coagulation procedure. The new design of a bipolar needle electrode permits the surgeon the use of a partial application of high frequency current for ITT. Less power is needed due to the limited current distribution at the immediate operation site, which means that it is not necessary to fix the neutral electrode to the patient. Thus an easy to handle and a highly safe procedure can be performed by the surgeon.
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