Improved reliability of repetitive RF interstitial heating in combination with brachytherapy: the effective use of...

Interstitial heating and brachytherapy are often combined in the treatment of cancer. In such instances, a needle-type internal electrode is inserted into the RALS (remotely controlled afterloading system) catheter instead of a radioactive source. A problem with this approach, however, is that the temperature distribution pattern generated by the inserted electrode varies at any given target region in each heating treatment, which makes it difficult to accurately replicate the heating treatment protocol. This variation is suspected to be caused by non-uniformity in the small gap between the internal electrode and the inner surface of the surrounding catheter, causing electric currents to flow between the electrode and the heating material, which differs from procedure to procedure. To solve this problem, the gap was filled with water of high permittivity, and the temperature distribution was investigated using phantoms. With this method, a stable and reproducible temperature rise distribution was obtained in the phantom experiment.