Reduced-order modeling for hyperthermia control

The feasibility of using reduced-order modeling techniques in the design of multiple-input, multiple-output (MIMO) hyperthermia temperature controllers is analyzed. State-space thermal models based on a finite-difference expansion of the bioheat transfer equation model of a scanned focused ultrasound system are created. These models are reduced using the balanced realization technique, and an order-reduction criterion is tabulated. Results show that a drastic reduction in model dimension can be achieved. The reduced-order model is then used to design a reduced-order optimal servomechanism controller for a two-scan input, two-thermocouple-output tissue model. A full-order optimal servomechanism controller is designed, and both controllers are applied to a variety of perturbed tissue thermal models to test the robust nature of the reduced-order controller. The comparison validates the use of open-loop balanced reduced-order models.