Periodic output feedback controller for cancer treatment with optimization

Abstract

The primary goal of hyperthermia controller is to achieve and maintain desired temperatures of ≥43°C within the tumor while limiting temperatures outside the tumor to safe levels ≤41°C from a baseline temperature of 37°C for a time duration of 30–60 minutes (3600 secs). The thermal model of the tissue is obtained by Pennes' bio-heat transfer equation and solved using finite difference method. A scanned focused ultrasound transducer is used to heat the tumor. The purpose of the controller for ultrasound hyperthermia treatment is to achieve the desired tumor temperature with an optimal rise time of 360 sec, a fast settling time of less than 720 sec with small oscillations. Therefore a Periodic Output Feedback (POF) Controller which is a type of multi-rate output feedback (MROF) technique is proposed. This control algorithm needs the system to be completely controllable and observable and can give the desired performance even in the presence of unmeasured disturbances. The performance of the periodic output feedback controller is tested on the 1-D model of the tissue. Using performance index minimization, the inter-sampling oscillations and the control efforts are reduced. Simulations are done by varying tumor size and thermal conductivity.