[The influencing factors and interfering effects in the control of the power distributions with the BSD-20000 hyperthermia ring system. 1. The clinical observables and phantom measurements].

A new generation of annular-phased-array systems BSD-2000 has been clinically applied in a pilot study. Therapeutic intratumoral temperatures greater than 42 degrees C were obtained in 15/15 sessions with six patients. However, the control of power deposition pattern has to be improved in order to increase the therapeutic gain and to guarantee an efficient therapy. A retrospective analysis of clinical phenomena has been performed by phantom set-ups because the power deposition pattern cannot be determined during therapy. Phantom measurement techniques are outlined, specifically phantom materials and visualization of power distributions. The problem of focus balance and frequency choice is illustrated by self-developed phantoms (liquid crystal sheets, light-emitting-diode-arrays). Especially, the limitation of modeling calculations is demonstrated.