MRI feedback control for phased array prostate hyperthermia

Temperature feedback control has the potential to enhance hyperthermia treatments by providing more uniform heating of the target volume and improving the response time required to reach therapeutic temperatures. A multivariable least squares algorithm was implemented using recursive and batch methods to provide on-line and off-line estimation of system parameters for simulated prostate hyperthermia treatments. A multi-input, multi-output (MIMO) Linear Quadratic Regulator (LQR) controller was implemented for simulated prostate hyperthermia treatments with a 64 element phased array. Control algorithms suitable for using magnetic resonance imaging (MRI) non-invasive measurements were investigated, taking into account issues relevant to MRI thermometry such as a large number of states (temperature measurements), a relatively slow sampling rate, and noise in the temperature information. An MRI compatible 62 element ultrasound phased array was constructed and tested in an MRI magnet. The phased array and control algorithms developed in the study have the potential to be incorporated into a non-invasive prostate hyperthermia system utilizing MRI feedback.