AN ADAPTIVE CONTROL METHOD FOR ULTRASOUND PROSTATE HYPERTHERMIA

摘要

For thermal treatment of prostate diseases, an ultrasound phased array was designed and operated with a computer controlled amplifier system which adjusted the power and phase of each transducer element. The clinical application of such a system is to increase the temperature in the prostate to 43-45oC and maintain the temperature for 30-60 minutes for a hyperthermia therapy treatment. In this paper, an adaptive self-tuning regulator (STR) controller has been designed and implemented with this hyperthermia system using a negative feedback transfer operator and a feed-forward transfer operator. The transfer operators' parameters were obtained directly from plant input and output with recursive least square estimation (RLSE). The advantage of this controller was that it did not need a priori knowledge of the tissue properties and could adaptively change its control variables according to the perfusion rate or other dynamic properties. Simulations indicated that the prostate reached the target temperature without overshoots and oscillations within 100 seconds. The system also successfully adapted to the dynamic tissue properties. Phantom experiments showed that the measured temperature tracked the reference temperature closely and reached the target temperature with a little oscillations and without overshoots within 150 seconds, which was consistent with the computer simulations.