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Proceedings Paper

Interstitial bipolar rf-thermotherapy (RFITT): therapy planning by computer simulation and MRI monitoring--a new concept for minimally invasive procedures
Author(s): Kai Desinger; Thomas Stein; Gerhard J. Mueller; Martin G. Mack; Thomas J. Vogl
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Paper Abstract

In addition to the laser, microwave or other energy sources, interstitial thermotherapy with radio-frequency current (RFITT) in bipolar technique has already been shown in vitro to be a safe and an economical alternative energy source with a comparable operating performance. The therapeutical application efficiency of these bipolar RF-needle applicators was evaluated using 3 different types of probes: standard, flushed and high performance cooled RF-probes (3 mm). These can be used to create large coagulation volumes in tissue such as for the palliative treatment of liver metastases or the therapy of the benign prostate hyperplasia. It was shown that the achievable lesion size resulting from the cooled RF-probes could be increased by a factor of three compared to a standard bipolar probe. With these bipolar power RF-applicators, coagulation dimensions of 5 cm length and 4 cm diameter with a power input of 40 watt could be achieved within 20 minutes. No carbonization and electrode tissue adherence was observed. Investigations in vitro with adapted RFITT-probes, using paramagnetic materials such as titanium alloys and high performance plastic, have shown that monitoring under MRI (Siemens Magnetom, 1.5 Tesla) allows visualization of the development of the spatial temperature distribution in tissue using an intermittent diagnostic and therapeutical application. This is no loss in performance compared to continuous applications. A ratio of 1:4 (15 s Thermal Flash MRI, 60 s RF-energy) has shown to be feasible. A computer simulation of the temperature and damage distribution during a bipolar RFITT application has been developed. The simulation works on-line with a RF-generator and measures the output power continuously. The electric power density (heat generating term) and the damage distribution is displayed graphically in real time.

Paper Details

Date Published: 2 April 1998
PDF: 13 pages
Proc. SPIE 3249, Surgical Applications of Energy, (2 April 1998);
Show Author Affiliations
Kai Desinger, Laser- und Medizin-Technologie gGmbH (Germany)
Thomas Stein, Institut fuer Medizinische/Technische Physik und Lasermedizin/Freie Univ. Berlin (Germany)
Gerhard J. Mueller, Laser- und Medizin-Technologie gGmbH and Institut fuer Medizinische/Technische Physik und (Germany)
Martin G. Mack, Universitatsklinikum Rudolf Virchow/Humboldt-Univ. zu Berlin (Germany)
Thomas J. Vogl, Universitatsklinikum Rudolf Virchow/Humboldt-Univ. zu Berlin (Germany)

Published in SPIE Proceedings Vol. 3249:
Surgical Applications of Energy
Thomas P. Ryan, Editor(s)

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