The feasibility of MRI feedback control for intracavitary phased array hyperthermia treatments

Temperature feedback control has the potential to enhance hyperthermia treatments by providing more uniform heating of the target volume and improving the transient temperature response. A multivariable least squares batch algorithm was used to estimate system parameters for simulated prostate hyperthermia treatments. A multi-input, multi-output (MIMO) linear quadratic regulator (LQR) controller was designed for prostate hyperthermia treatments with an intracavitary phased array. A parametric study was performed for the one-dimensional control case, investigating factors relevant to magnetic resonance imaging (MRI) feedback control such as spatial resolution of temperature measurements (size of the averaging volume), sampling rate (image acquisition time), thermometry noise, control width, control depth, physiological parameter changes and reference input structure. Simulations utilizing the two dimensional (2-D) thermometry of MRI and the 2-D focusing capabilities of phased arrays demonstrated that near field heating can be controlled such that the size and shape of the heated volume can be tailored in 2-D. The control algorithms developed in this study show promising potential for incorporation into a noninvasive prostate hyperthermia system utilizing MRI feedback.